All posts by Seamus Sheehy

Self Builder Passive House

Self Build-Building a New Home-Self Builder

Factory Built or Site Construction 

There are many options today when deciding to build. One can use a factory built design or use traditional block work or timber frame on site. Some factory built designs are as follows by way of example .  One can select the level of input oneself such as only construct the frame and say the self builder can do the rest or let the builder/supplier do everything.

How much Work does a self builder take on.

As a self builder I would try and get the foundation, frame, roof and windows installed then one can work in the dry to finish it. One is left with indoor wall completion, plastering , air tightness, Heat recovery, Wiring, Plumbing, Rain Water Harvesting, House heating System, Water heating system, floor finish, Painting, furniture , kitchen more than enough work for the self builder. The above need to be well thought out before laying the foundation or erecting the frame and the finish design of the roof.

The Building Standards-Self Build

One needs to comply with the building regulations. Always remember these are the minimum standard. It is always better to go for a home that will last well into the future that is warm and supplies fresh air.  A lot of new homes built today are of a poor standard and this can be seen in the UK and Ireland. See example

The Sales Pitch

There are buildings that can receive different rating systems such as  LEED and BREEAM.  A good video on the good, the bad and the ugly of these can be seen here.  They focus on equipment and energy accessories so it is best to leave these and focus on the basics. What are the basics –Insulation, Air-tightness, WindowsHeat Recovery (fresh air supply), and minimising thermal bridging (heat loss through details on the build).  When one does the above one finds that the heating system is simple, the house costs very little to run and is healthy if the correct materials are selected and installed in correct sequence during the build.

The Gold Standard-Passive House

The highest energy standard to build a house , an apartment, school or commercial buildings is the passive house standard. It focuses on the basics and uses physics rather than rating systems to design the building.  All the calculations are done before the house is built on a passive house planning software package (PHPP) which takes into account for example how much solar heat the glass in the window will leave into the house, how much heat will be lost through the glass from the inside to outside, how much heat is lost through the frame, and the heat lost on how the window is installed in the wall. Every building detail physics are analysised to ensure that one ends up with a comfortable home.


Self-Build Solar PV , MPPT Chargers and Outdoor Lighting

Self Build the plan-Solar PV

The plan is to have all the outdoor lighting (Using LED -Light Emitting  Diodes) operate from a 12 volt recycled car battery and recharged by a solar PV panel. The lights will be controlled by the in-built timer in the MPPT charger. This will keep the cable cost to a minimum (small cable size) and keep the voltage low enough to be safe in a garden environment (when digging and planting).

Parts Required

Below is the CIS thin-film solar PV Panel (copper indium gallium selenide )  I mounted on the shed roof.

Solar PV Panel
Solar Battery Charger


I selected a 60 watt solar PV panel that was manufactured using CIS . This type of panel has a higher output voltage of 52 volts which work better with the  charger I selected rather than the typical mono  or poly crystalline cells of 30 volts . One needs to select a charger to suit the PV one buys. The panel was mounted on a 3 degree pitch facing south (see above) . During tests I found that this type of cell is more forgiving for shading and dirt (bird droppings mainly)-it maintains a consistent output power . For example when I partially shaded it with my hand it still outputs almost the same power. If one partially shades a monocrystiline /polycrystaline cell it will cause it to stop working as all the cells in the unit are wired in series.

Measuring the efficiency of the installation.

In order to check the efficiency I mounted a pyranometer at the same angle (top left of image) so that I could ensure that connections and charger were working correctly. One needs to know the input power in order to check the charger efficiency and that the system is working correctly.

The MPPT Battery Charger

Victron 75/15After reviewing products available I opted for the Victron SmartSolarCharger MPPT 75/15.  This can charge a 12v or 24v battery system. When selecting a unit one needs an inbuilt MPPT which stands for Maximum Power Point Tracker. In Ireland and the UK this is  important because of our natural cloudy weather which causes the solar panels to vary their output as the irradiance changes .  What happens is that the solar panel’s internal resistance changes when the irradiance changes (sun shining on panel) -so the job of the MPPT charger is to change its load resistance as the solar panel’s internal resistance changes.  When the load resistance matches the solar panel resistance then the maximum energy can be transferred to the load. If a charger did not have the MPPT then the efficiency of the complete system would be compromised. While there are different methods (algorithms) used  to build MPPT units some are more efficient than others. Some of the different MPPT design options available are called perturb and observe , Incremental Conductance , short circuit current method etc., The idea of all these MPPT systems is to get the maximum power from the solar panel -some MPPT are low cost and others are more efficient in cloudy weather.

Solar PV Charger

There are a number of advantages of the unit compared to others that I researched . It has charging algorithms for different battery types such as deep cycle and lithium ion.  It has a bluetooth connection so that one can programme and monitor the output without other devices /connections being required. Another advantage is that it has a lighting timer that can automatically switch lights on and off at night or at dawn.



Some of the advertised benefits of the Victron MPPT unit are:

Victron MPPT Charger






The Setup .

The setup is as follows . I plan to move the battery out of the shed as it is not best practise to have any battery system in a shed/garage/house because of the fire risk. The charger is mounted on a fire resistant material (Magnesium Board)









In order to access the data collected one logs on using the Bluetooth connection on your phone/tablet and the data is available. Below are different samples of the data available . The first indicates the solar power collected and the load usage. If the battery is fully charged it will take little or no power. If there is a load during the sunshine hours then the battery and solar panel will supply it.

Data Collected








Below is a chart showing how the MPPT charger adjusts its output/load to follow the changes in the irradiance levels (power from the sun) per second .

MPPT Irradiance Changes








As I am able to measure the input power using a pyranometer I built I was able to see that the system was working efficiently. The data below is the output power from the charge controller when the input power from the sun was 471 watts/m2.  The CIS panel provides 60 watts output when the irradiance is 1000 watts/m2 at STD (Standard Test Conditions) . This would mean that if the input power was 500 watts/m2 then the output would be 30 watts/m2. The data from the charge controller indicates an output power of approximately 27 w/m2 for the 471 watt/m2 input power.

Output power when Solar Irradiance input power is 471W/m2.



Self Build Remote Monitoring Passive House

Self-Build for Water Leaks, Power Measurement and Temperature.

The task of monitoring for water leaks, temperature and measuring power is best served by some remote tools available on the market.

Most tools rely on Wi-Fi, zigbee, 433mHz etc., signals to communicate through the internet connection remotely to your phone.

This in itself is a weakness as if your wi-fi is not working then most of these tools fail. But if the wi-fi or ethernet connection does not fail then these tools are of value.

Lets look at some of these tools that I feel are worth considering.

sonoff 433 RF Bridge
Water Leak Passive House









The lowest cost unit is the Sonoff suite of products. The list is comprehensive and the cost is low. For example the wi-fi / 433Mhz central hub for these devices costs less than €9.00 and as an example the water leak sensors are approximately €8 each and it uses a lithium battery for reliability (needs to be purchased separately).

Water Leak Passive House
Purchase Lithium batteries separately .







The product is  very well made and a certain level of IT skill is involved in setting these up. It operates at a very safe radio frequency like that of your car remote control rather than higher frequency’s but the hub uses wifi so if one keeps it close to your router and keep the router as faraway as possible from you it is probably the best approach.

I would advise that a separate sensor unit (regardless of which product you select)  is installed in a location that you can easily check to ensure that the system is functioning correctly as water leak sensors can end up in locations that are difficult to inspect and check such as behind dishwashers etc. One needs to change the battery every year or two on each of the sensors or when your test unit fails.

Next on the list is the Samsung smarthings hub and sensors

Samsung Smart Things







This type of device links to other well know products such as Amazon Alexa and costs around €90. They also provide water leak sensors to connect to the above. This will be easiest to set up.

Multiple options are available to integrate with the above

Type in smarthings hub in the search of their web site and one should find the relevant devices . Check your own country samsung web site for compatibility.

Another company that provides value is Shelly. They supply multiple sensor types including water leak sensors that integrate with the power unit below.

Power Measurement

I have not purchased this unit but it looks like good value at €69 but it uses wifi. It is made by Shelly

Power Measurement








A unit that measure power consumption and provides a Bluetooth option also looks like good value. It is the AT3010 AC50~320V 100A 3KKW Phone App AC Meter. It costs around €15 and can be purchased from .  It will need an enclosure to house the unit and it does not use wifi which is a benefit. I purchased this unit as a test and I am about to set it up.  I will use this meter to monitor the cost of heating the house and also monitor the condition of each storage heater.

Power Measurement

Lighting and KNX Update


I am just getting around to installing the light switches . This is how the finished light switches look at the moment. Later on I plan to change the front plate of this switch to one of the other options such as glass, wood or marble.

This is what the above light switch looked like before installation. Standard switches can be used if one uses the method described below. I used a screened alarm cable to connect the KNX binary device known as a universal interface. This voltage is extra low around 3 volts DC.

KNX Distribution Board

As seen above this is what a typical KNX lighting distribution board looks like. One has a Power Supply (top left) and a programming Interface (next to power supply) . The three actuators (12 way) on separate rows send power directly to the rooms or other devices such as towel heaters. Functionality such as timers, last state before power failure, purging (automatically switching on pumps/valves to ensure they do not stall) etc is already built into the KNX technology.


This is one type of LED Driver I have used to power each LED. Typically when one buys an LED they have already tried to fit all the electronics contained in the above unit in the lamp one buys . This is one reason why led lamps do not always live up to their expected life time of 50,000 hours. The majority of LED failures are due to heat stress. I am using 9 watt LED in the housings shown above and the Power supply is a separate unit. For lower power LEDs one requires less electronics.

Self Build-Images and Lighting Design Progress.

Progress to date.

Passive House

Floor Laying

Floor laying continues with the Junckers System. The floor boards  are 22 mm solid wood with a proprietary clip system. Each of the metal clips (shown below) connect each floor board. The clip type one selects depends on the expected humidity levels in the home. I used a soundproof underlay on the concrete floor. One can also nail this type of flooring.


Skirting Board Lighting

I started the design of the skirting board lighting that will be powered from a DC source (battery) connected to a solar panel. The idea is that this lighting would be on when it is dark and would also act as a lighting system if there was a power failure in order to minimise the use of candles.

The light output of this lighting would be equivalent to a candle and they are placed in bathrooms and corridors in order to allow one to walk around the house at night without switching on the main lights.

A first fix of how they will look is as shown below.




Heat Recovery Ventilation (HRV) Selection Part 3

Mounting of HRV Unit

Different HRV units have different mounting options. Some are floor only, wall only or ceiling or all three. Some units like the Airflow DV145 that I purchased can be mounted on the floor or wall while smaller Airflow units can be mounted on the ceiling, floor or wall. One needs to make sure that there is space underneath for the condensing water outlet.  If the unit is mounted on a wall make sure that vibrations do not interfere with noise sensitive rooms such as bedrooms. I mounted ours on a sound proof and isolated base and used other sound proof methods to isolate it from an adjacent room.

In the early stages of the build the fresh air inlet and stale air duct positions were selected with a spacing of over 2 metres. If the supply and exhaust ducts are too close this can interfere with the correct operation of the HRV unit. This entailed finding an HRV unit that would be flexible in the options available to simplify the space required for the main ducts and keep the runs as short as possible. The lengths of the supply and exhaust ducts play a big factor in the efficiency of the whole system. The Airflow unit comes in a right hand and left hand model. I found that different manufacturers have different duct layouts even though they have Right Hand and Left Hand models.

DATA from the HRV with the Post Heater On

HRV Data
HRV data February 2019 with post heater on

One can see from the above graph that with the winter sun I needed to switch of the heater and switch to summer bypass. The next plan is to automate the bypass mode when the solar irradiance level measured in W/m2 and temperature exceed a set value then the HRV would automatically switch over to the summer bypass mode as one is gaining solar heat.

HRV Soundproofing

As the internal fans are to the rear of the unit I added a small amount of soundproofing as an experiment. I was able to reduce the db level from 49 db to 44 db. Each 3 db approximately equates to twice as loud or twice as quite depending on whether you are increasing or decreasing the level.

I mounted the unit in the hallway entrance so extra sound proofing was required. If one has a utility room then  extra sound proofing would not be necessary I feel.

HRV Efficiency

Following on from the previous blog I had a display panel built that calculates the HRV efficiency using the supply method and extract method by means of the Modbus data connection available in the HRV unit . In the Image below one can see S100 (Supply method for calculating efficiency) and the E 90 (Extract method ) as a percentage.  The supply method is the one typically used by manufacturers in brochures. The D  displays the difference .

HRV Efficiency









The top line displays the temperatures of the Inside air and the air leaving the house followed by the Outside air temperature and the supply air temperature to the house.  When the post heater is on the efficiency calculated with the supply method sometimes displays a number greater than 100% as the heater is built into the unit and mounted before the thermostat.  The extract method for calculating the efficiency is a closer representation of the real efficiency and it is similar to the passive house method (uses the same principle ). The extract method does not use the supply air temperature in the formulae.

Access for repair and maintenance.

Some HRV units require side panel access so ensure that you have enough space to get access to fans/ filters for cleaning and maintenance . The Airflow DV145 can be fully maintained from the front cover so it can be fitted in a corner space without restricting future access to internal parts. The filters are also maintained from the front panel.

Functions and Benefits

When selecting a unit- what was important to me that there was an integrated summer bypass function in the unit,  software control by a smartphone with data capture (a manual control panel-is an extra cost and another item that could fail) and an integrated post electric heater.  Airflow also sell a ground source heat pump option connection to the HRV which I did not purchase. For those installing a stove / fireplace one requires a Fireplace function built into the HRV . The Airflow DV145 has this function.

September 2018 performance.

HRV Software review and Control.
Example of HRV in use in our home.


Summer Bypass

The summer bypass function allows one to bypass the heat recovery function during warm weather or reduce winter sun peaks (when the sun is low on the horizon). The way this works is to bring the air outside directly through the ducts in order to reduce the internal temperature at night or during the day. One can see from the image above on the 28 and 29th of September I forced the HRV unit to summer bypass during the day to keep the temperate under control with the winter sun. No heating had been switched on for the month of September and the night temperature outside has hit the lowest in the same month of 2 degrees.

The Airflow unit is software controlled by means of your phone or your personal computer . This helps keep the HRV cost down, gives remote control and it provides data for analysis. The physical manual control panels in general cost €200 or more.

The post heater in the Airflow DV145 unit has a PWM (pulse width modulation) heating element control which means that it can control the switching of the heater within a fine tolerance for heating the air rather than just switching the heater On and Off.  The reason I installed this was really to provide a back up option to the main house heating system (approximately €200 extra).

House Heating System

The house heating is currently designed around two storage heaters of 1.7 kw each to heat the house using off peak electricity and operate for 7 hours a day. I picked up one unit for free and the other unit cost €70.  I suppose one could say that the total capital cost of the heating system was €270 when one adds the HRV post heater.

For the month of October one of these heaters was switched on for 14 days.  The post heater also improves the frost protection functionality within the HRV and helps maintain a heating level of 21 degrees Celsius throughout the house.

Below is an example of how the HRV switches on different heating loads in the post heater while maintaining a set temperature . The time interval below is over 60 seconds (full screen view) and the heater appears to adjust the power output required continuously to maintain the set temperature.

Post Heater HRV
Post Heater being switched on and off approximately six times in a minute with different heating outputs.



Duct work for primary supply and extract

I selected an insulated 210mm EPS duct for the extract pipe as this duct carries the coldest air from the HRV unit .






Supply and Connecting Manifold Ducts

There are a number of options. My understanding is that the larger duct systems such as 150mm feeding multiple rooms with silencers is the best option if one can accommodate this in the build early on and find a good designer. I opted for the 91mm semi rigid ducts using a manifold system from and I am very happy with the low noise level and amount of air being delivered throughout the house. I use a co2 sensor to monitor how the flow rates are working in different rooms.

Hiding Ductwork

When one is designing a house to the passive house standard or installing an HRV unit in an energy efficient /airtight house one can reduce the cost on the system if one plans the service routes of the ducts early on and selects particular joist types. It is expensive to batten and counter batten to hide the ducts afterwards as one needs to try and keep the duct-work within the airtight envelope.

I opted for the manifold system using the largest semi rigid ducts I could find. These were the Fraenkische-profi-air classic pipe with an internal diameter of 78mm and outside diameter of 91mm. The larger the duct the lower the air friction and noise when delivering air to rooms such as bedrooms. These ducts are also anti-static and low emission.

Below are the choices I came across from the semi rigid range. The white duct is made by Fraenkische.








Connection ducts from Manifold to HRV.

For the ducts that connect between the main HRV unit and the manifold I used an insulated flexible sound reducing duct (as seen below).  This is made up of an inner foil with sound reducing properties, next an airtight plastic membrane and then insulation followed by another layer of foil. The inner rim is re-enforced with a steel wire to provide rigidity.  It is time consuming connecting this up but it appears to have done its job.

HRV Duct
HRV ductwork

Contact Details:

Heat Recovery Ventilation (HRV) Selection Part 2

Selection of the HRV unit.

For those building to the Passive House standard the HRV is independently tested by the Passive House Institute. They provide a full list of certified units at the following link Passive House Certified Heat Recovery Units.   

HRV Efficiency (How is it calculated)

There are principally three methods it seems. One is the Supply method (used by manufactures) and this usually gives a higher efficiency value than the real world values. The Extract efficiency method is used to give a closer to real world value and then the passive house efficiency method which adds the following formulae to the Extract efficiency method.

Pel = real electrical power, W
M = mass flow, kg/h
Cp = specific heat of the air, kJ/kgK

The good news is that it appears if the HRV is certified to the Passive House standard then the difference between the supply method and the extract method  is very small.

In the near future I plan to connect to the HRV unit I purchased and view the efficiency values.

The Passive House certificate shows the following

HRV Calculation


Cost Efficiency

The most cost efficient unit I came across was the Airflow DV145 passive house certified unit for our 200 m2 house with an airflow capacity of 542 m3/h. I paid around €2200 for it. If one has a smaller floor area then more savings can be made by using a smaller unit. As a self builder technical support was important and their main offices are in the UK.

If one opts for a non-certified HRV unit a 12% reduction must be applied to the manufacturers specification . Some manufacturers might not renew the certificate each year so it is a good idea to ask if a certificate exists. The data must be entered in the planning software for the passive house. For those interested in the passive house planning software (PHPP)  there are courses run in Ireland frequently so I would suggest that one does this 3 day course (typical) and usually one finds the software discounted on the course.

It is an enjoyable course where one can select your own pace (the first time I did the course I wanted to listen and learn rather than calculate the performance of our own home). One such place is

HRV Self BuildTo be continued………


Contact Details:

Heat Recovery Ventilation (HRV) Selection- Part 1


There are two types of HRV units that I came across -Heat (HRV) or Energy (ERV). The ERV is used principally for recovering humidity  and heat. I selected a HRV unit,

Size Matters

When selecting a HRV unit it appears that one of the biggest mistakes is to select a unit that is too small but still satisfies the current regulations. What appears to happen in the competitive world of quotations is that a unit that just ticks the box comes in as the best price.

In selecting a unit for our home I selected a unit that has a manufacturers capacity of 542m3/h where the floor area of our house is 205 m2. Currently the unit is running at 31% of its capacity and it is maintaining a CO2 (Carbon Dioxide) level of around 700 ppm when the four of us occupy it . I use a stand alone CO2 sensor to measure the CO2 in different rooms. (I have not commissioned the unit yet as the internal doors/glazing are not installed).  

Another advantage of selecting a larger unit is that it can run more efficiently at lower speeds and generates less noise through the ducts or from the unit itself.

Some of the options from the manufacturer Airflow (my unit is the third from the right).

HRV passive house
A choice from one particular manufacturer.

September 2018 performance (with no heating switched on yet).

The graph below gives an idea of how the HRV works when managing heat from the house and supplying fresh air. For the coldest days of the year so far (2 degrees at night-in September) I put the unit into summer bypass mode the next morning (take in outside air directly and pump it around the house) because the sun was shining that day. The winter sun is lower in the sky so solar gain increases in the winter (when the sun shines). The house is made of timber/glulam construction. The main thermal mass is the concrete floor at the moment soon to be covered by a 32 mm thick wooden floor so the response times of house I suspect will change. The floor and wall temperatures are approximately 22 degrees Celsius.

HRV Software review and Control.

Example above of HRV in use in our home.

Sample Data in our home using Google Fusion to visualise the HRV data for a week in October. (see link below)

  • One can select the chart tab and visualise the graph.
  • Use the bottom graph to zoom in.
  • The data is from the 21 October to the 28 October 2018.
  • One storage heater rated at 1.7kwh was used for 5.5 hours a day off peak.
  • The storage heater was switched off for one day on the 23rd October.
  • The graph starts at midnight on the 21 October.
  • Each ref reading is every 10 minutes.
  • The CO2 reading vary between 480ppm and 700ppm when fully occupied.


All HRV units contain a maintainable part called filters. They have a number of functions.

  • Clean the air being pumped into the house, and
  • Keep the internal components such as fans, ducts and HRV housing clean.

One typically finds one coarse filter and one fine filter on the air supply into the house and a coarse filter on the extract air from the house before the extract fan. The coarse filter is typically a G4 and the fine filter is a F7 (Pollen filter). I installed a 400mm x 400mm  G4 coarse filter at the duct inlet so that I could keep the main supply duct clean. It is a bit more effort to maintain this but it will hopefully minimise the maintenance of the duct.

To be continued………


Air tightness Test-Passive House 0.22ACH

Self Build air tightness test -0.22ach with a volume of 603 m3 @ 50 pascals. 

When one is building to a performance standard the day of reckoning is the airtight test. The reason for this is that when one is pumping fresh air into the house using a Heat Recovery System, rather than relying on simple multiple holes in the wall, it becomes important to control where the fresh air is coming from and where the heat is going.

Airtight Test
Airtight Test







If air is leaking in or out around windows /doors/walls or other gaps in the building fabric then heat is lost and moisture problems in the form of mould can arise or else give rise to damage to the building fabric.

The pressure 50 pascals equates to a 20 mile per hour wind which is not too untypical in Ireland. So if one opts for the Irish  building standard (a minimum standard) this equates to the air in the house changing/leaking 7 times a hour when a wind blows at 20 miles per hour. No wonder people block up the hole in the wall vents .

  • The current Irish building standard  require 7 air changes  per hour (ach) also called leakage at 50 pascals  typically with no heat recovery system As a guidance heat recovery manufactures recommend 3 Air leakages per hour to ensure that the heat recovery system can push fresh air into the house and recover heat leaving the house through its own system rather than through gaps in the building fabric.
  • The passive house standard for a new house requires 0.6 Air changes per hour (ach) at 50 pascals to ensure the heat recovery system works efficiently, ensure that occupants receive the correct amount of fresh air and minimise building fabric damage.

The passive house test differs from the Irish test because it must include pressurisation and depressurisation and use the volume as set out per Vn50 (EN13829).

The Test

Gavin O Shea from Greenbuild was hired for the job.  He is certified/audited by the National Standards Authority of Ireland (NSAI).

The preparation for this entailed sealing all cable ducts and the inlet and outlet pipes for the Heat Recovery System. One also ensures that the shower and sink outlet traps are full of water. The overflow outlet for two water tanks were not sealed off. I did consider a duck valve but it was not in place at the time of the test.

Air Tight Test
Airtight Test









The test using the Irish method gave a result of 0.181 m3

Gavin O Shea calculated that the equivalent size hole that equates to a result of 0.22 ach is approximately 65.25 cm2 (@50Pa) or a hole 81mm x 81mm if all of the leaks present in the dwelling were concentrated into one hole. That is about a tenth of an A4 sheet of paper.

The results of the air tight test can also help determine the selection of the  Heat Recovery System. If the airtight test is lower then more options are available when selecting a unit.

From my research a passive house standard Heat Recovery Unit will cost more because it needs to be independently tested by the Passive House Institute using their test method. Heat Recovery manufactures have also the burden of putting the unit through national tests or international tests with the end result being the customer pays more.  One has also the option to select a non passive house certified unit for a passive house but when calculating the performance value one needs to account for this in the PHPP software with a 12% reduction below the manufacturers performance claim.

If one wants to view certified Heat Recovery Units one can find and sort them at the following link.  One can see for example at this link the capacity (Column- Air Flow Range) that these units have as it is important to select a unit that is oversized for your particular self build. I would compare it to selecting a mini car to tow a caravan up a hill compared to using a larger car. The small car will struggle from an efficiency and noise point of view while the larger car will be quieter and more efficient at the require flow rates.  I will do a separate post on how I selected our Heat Recovery Unit.









Plumbing Update

Water Switch On.

I finally switched on the water supply to the house and then checked the compression connections on the gravity based system for leaks. The reason for using the gravity based system was to keep everything as simple as possible,  consume the lowest amount of energy and have a system that would be low in maintenance cost.  All the joint connections were brass compression fittings and I used a pipe called  “qual-pex” .  I insulated the cold and  hot water pipes for both the rainwater and the calorifier tank.

Gravity Tank 

I installed a  separate gravity tank for the toilets that will be fed from the rainwater tank in the garden eventually. I need to design a control unit to pump rainwater when required and operate from the mains to flush out the gravity tank at regular intervals. At the moment it is connected to the fresh water supply for testing.  This tank was mounted 2.71 metres above floor level.  Nylon washers were placed inside and outside of the tank brass connections fittings.

Storage Tank Connections








What worked for me in relation to the toilets was an 1/2 inch pipe that ran a distance of 15 metres approximately with a storage tank base to floor height of 2.71 meters and this enabled the cistern to fill in approximately 1 minute 45 seconds.

Lessons Learned

  • When tightening compression fittings- a good bit of advice is always leave room for an extra turn on the thread. In this way if there is a leak one can tighten the compression joint further.
  • On the calorifier connections use Jet Blue Plus paste or similar paste and check it is suitable for potable water.
  • The longest run was approximately 20 meters of 1/2 qual-pex and this  supplies enough pressure for a “natural” water flow at the furthest away sink outlet-I also removed the filter in the outlet of the tap to further increase the water flow.
  • Certain isolation On-Off valves have bore diameters that are smaller than the diameter of the pipe bore further reducing the capacity of the water flow. Visually check before purchase.
  • Check that the taps and shower fittings are designed for a gravity system. I used a tap that had a minimum operating pressure of 0.1 bar from the Grohe range (1 metre height of water is = 0.1 bar).
  • I was unaware of what an air lock can look like . In one case no water flowed and in another case I had a constant trickle of water with no air gurgling. To get rid of the air lock I used a small 5 litre pressure sprayer with a silicone hose on the end.Pressure Sprayer




  • Use copper inserts instead of nylon on “qual-pex” when trying to get gravity to work in your favour . They have a wider bore (see below).

Qual-Pex Inserts Copper and Plastic
Copper versus Plastic Inserts









Toilet Cistern

As most of the inlet valves on toilet cisterns are now designed for high pressure they come with a restriction devices and sometimes a filter. For use on the gravity system I removed these.

I plan to filter the water at the feed end of the water supply.  Both the toilet storage tank and the calorifier storage tank (supply’s the hot water) are within the thermal envelope. This means that the tanks will not freeze but this brings other issues to be dealt with, such as noise from filling and potential condensation. I installed rockwool insulation around the tank to minimise temperature differences of the indoor air and reduce the noise of water filling the tank as I have no attic space.

The original toilet had a bottom inlet valve made with plastic threads which proved difficult to install.

Cistern Inlet Valve


I did have problems with the original cistern valve where I cross threaded the plastic connection (which resulted in a leak) as one finds that space is limited under a toilet/cistern (see below).

Toilet Cistern with Penny valve for turning water off and on at the toilet.
Toilet Cistern Connection









Another problem I had was I could not get it to operate correctly from the gravity tank. To solve the above I replaced the inlet valve with a Jollyfill telescopic Wirquin brass inlet valve and removed the high pressure device.

Wirquin Bottom Inlet Valve









When I installed  the inlet valve the connection leaked between the rubber seal and cistern. I removed it and placed silicone above the rubber seal. The silicone cured the problem.


The gravity flow rate proved too low for the shower valve temperature control to work so plan B was acted on. I installed a 1.5 Bar 250w pump to raise the flow rate.

It is a Salamander RP50PT pump (45.5 dBA) . It cost €200 including postage. I am impressed with the low non-intrusive noise it generates. It comes with small sound isolating pads. One can roughly equate a 3dBA increase with twice the loudness.

Another factor to take into account when selecting  and sizing a pump for one, two or three shower units is that the power usage approximately doubles when one selects a 0.5 bar increase for this range of pumps.  So If one is sizing for the use of 3 showers being on at the same time (using one 3 bar pump) and only one  shower is on then one will be using 1000 watts of power most of the time . I feel it is more energy efficient to install separate pumps and in this way one uses the least amount of energy most of the time and the pump will also be quieter as noise increases also with each 0.5 bar of pressure.

Shower Pump