A common belief is that replacing a gravity system with a combination boiler will improve your showers in a home but for some customers its far from the truth.
I would strongly recommend that you do a flow test before allowing the plumber to rip out your old system as sadly in this country it is common for a plumber to make changes and then walk away from the problem or worst still expect you the customer to pay him thousands of £s to rectify the problem he caused. Before you spend a fortune you can carry out your own tests or insist your plumber carries out these tests before you fit a combi boiler.
WRightChoice Dynamic Pressure Testing Kits can be purchased from Alan Wright
If you are reading this article after already fitting a combination boiler and you have issues then a ShowerPowerBooster may be the solution you need.
To purchase a pump you can buy by using the buy now button above or visit our home page and follow the links. If in doubt please contact our technical team on 01928 620 099 or email SPB@flowflex.com (out of hours email alanderekwright@icloud.com )
In the absence of common sense advice from your plumber it is important that you the customer are aware of the science that underpins the decision to take out your combination boiler. PLEASE READ MORE
A combination boiler has two critical needs to work in your home and this is dependant upon the volume of water that your incoming service pipe can supply to your boiler and the pressure of the water at that supply volume.
I am writing this blog in response to a question I received today:-
I am a homeowner who is about to undergo a small renovation project which will include adding a ensuite within the loft, giving me two baths in total. I wanted to replace my exisitng conventional boiler with a system boiler, mainly because I am told a combi cannot handle more than 1 shower at a time. Do your pumps/ products, get around this problem and allow me to get a suitable flow rate to my ensuite shower, if for example the kitchen hot taps are on?
My flow rate of the mains has been measured at 9l/min. I am based in Bromley, Kent.
First of all we should look at volume and answer the question:- ‘Can I get enough water to my boiler.’
The output of a combination boiler is dependant upon the KW output of the boiler.
The bigger the boiler the more water you need and the output you can expect from your boiler is:-
The maximum flow from a Combi Boiler is determined by its KW rating and in winter, because water is colder, the output is less:-
24 KW Combi Boiler gives 11.5 litres a minute (2 showers)
30 KW Combi Boiler gives 14.5 litres a minute (2.4 showers)
42 KW Combi Boiler gives 20.0 litres a minute (3 showers)
The flow rate can be measured with a measuring jug and because the flow rate in summer is greater add 20% to the flow rates above and can this be achieved where your boiler is being fitted?
The second question that needs to be answered is at the maximum flow rate is there enough pressure where your boiler is being fitted. The MINIMUM pressure required is 1 bar (10 metres head).
The answer to the question I received today is rather simple. 9 litres a minute is nowhere near enough water for a combination boiler. You need to keep the 225 litre cold water storage tank.
