# Replumbed house - Combi installed - Pressure too low



## spreadsheet (23 May 2009)

I'm in the final stages of finishing my house refurbishment and just switching on the water after a full re-plumb.

I went for the option of installing a combi-boiler to do away with the hot water cylinder and attic water tank.

However it's looking like the incoming water pressure is too low. The shower is barely ok when switched on full, but if you flush both toilets, the shower goes back to a trickle for 10 minutes. 

The plumber installed an outside tap beside the boiler house which comes off the mains supply before the mains goes into the boiler. If I turn on this tap whilst running the shower indoors, the boiler effectively turns off. The outside tap pressure seems great though. 

The details are as follows:

2 bed mid terrace, Dublin 8
Natural Gas connected
Underfloor heating downstairs.
Dishwasher, washing machine, kitchen taps to be connected.
2 toilets, one upstairs and one downstairs with wash hand basins
Aqualisa iLux Digital shower and bath filler.
Sargon 30 combination boiler
4 radiators

The heating system hasn't been tested yet.

My questions are:
How can I get the water pressure increased?
Is it possible to pump the mains pressure coming in?
If I put a tank in the attic would that be sufficient?
Could I still drink the water from the tank if I put it in?

Thanks for taking the time to read this!


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## gary71 (23 May 2009)

It would be a basic requirement before a combi is fitted to confirm the mains water pressure meets the minimum requirements , because this wasn't done you now have a boiler that is not suitable for your property which is something i come across a lot, unfortunately you cannot pump the mains as you can't suck out whats not there but that doesn't stop nutters from fitting them anyway, what some installers will do is fit a break tank(not for drinking) which is just your mains held in a tank fed by a ball valve, this water can then be pumped giving you good pressure, the problem with this is it's really a set up for stored water, normally a unvented cylinder this makes it easer to workout the size of the break tank, i have yet to come across a combi fitted to a break tank which worked properly the tanks are to small, you would need to figure out the volume of water you would need under maximum use and store that amount of water which would have a great weight if fitted in the loft, the chances are you're "plumber" will go with the break tank and if it's to small it will still work sort of and most people learn to live with it, after all the doom and gloom you may want to check that there is nothing on the boiler slowing down the flow you can do this by running your cold tap in side and seeing if it slows up in the same way as the hot, good luck, Gary.


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## spreadsheet (24 May 2009)

Thanks for the detailed response Gary!
I imagine you could be right and the plumber will suggest a break tank of some sort.

I've been searching around the web and there were some sites which mentioned using a cold water accumulator or booster system like the ones below:

[broken link removed]

http://www.grundfos.co.uk/web/homeUK.nsf/Webopslag/DMAR-6RZKWV

Would any of these serve my purpose?
I'd like the water to stay drinkable if possible. I'd also be reluctant to run new pipes to the attic as the place is plastered and half decorated.


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## DavyJones (24 May 2009)

Everything Gary has posted is correct. I would be unhappy with installer. The first thing an installer should do is check incoming pressure and pipe size to determine if it needs upgradeing.

You could run fresh water to kitchen tap only and run everything else off your tank.

It is illegal to fit pump to mains.


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## glenamaddy (24 May 2009)

spreadsheet said:


> I'm in the final stages of finishing my house refurbishment and just switching on the water after a full re-plumb.
> 
> I went for the option of installing a combi-boiler to do away with the hot water cylinder and attic water tank.


 


DavyJones said:


> I would be unhappy with installer. The first thing an installer should do is check incoming pressure and pipe size to determine if it needs upgradeing.


 
Davyjones, Maybe Spreadsheet *specified* a combi boiler setup.


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## DavyJones (24 May 2009)

glenamaddy said:


> Davyjones, Maybe Spreadsheet *specified* a combi boiler setup.




Thats beside the point. They hired a professional and didn't get a professional service I.E even if it has specified by other, Installers job is to advice on why it can't be done because they are responsible for the end product working.

Most people involved in their own self builds etc don't have much of an idea of the tecnical side of the build and this is why they hired experts.


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## gary71 (24 May 2009)

glenamaddy said:


> Davyjones, Maybe Spreadsheet *specified* a combi boiler setup.


 
A installer either knows there job or they don't, to fit any kind of product without confirming if it's suitable is just mental, i see combis run off pumped mains and break tanks a lot and they're just crap installations and to blame the house holder is poor, you tell me another profession with manufactures instructions covering all aspects of the installation from the start to the finish, that includes pictures some of them colour and to still get it wrong? now thats stupid and costly. Gary.


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## gary71 (24 May 2009)

spreadsheet, unfortunately you have a boiler that is not suitable for the purpose that you wish to use it for, you are kind of in square peg round hole time, what ever you do the boiler will not work as the manufactures have designed it to work, as you would require decent water pressure and it would need to be constant, you could try the accumulator or booster system which i feel would work better than a small break tank, but you would still have the problem of running out of water after a given time, most people in the situation you are in do come up with a answer to the problem and learn to live with it, you have to decide how much hot water you think you are going to need ie one bath, two baths etc.. and then try to design the system to give you that, Gary.


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## DGOBS (24 May 2009)

In three words ........DUTY OF CARE

As for mental installs I believe you got a call the other day Gary about a Britony Combi Plus about the valves being removed from diverters cos installer can't wire a system!

Gary you got any knowledge on these intergas boilers? Good or bad


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## gary71 (24 May 2009)

Hi Tony, i had a long chat with those installers but unfortunately i couldn't get them to understand what they had in front of them, in regards to the Intergas boilers i haven't worked on them, but i do think now days it more to do with aftercare service and parts availability than build quality as boilers are being built better(as you know) Gary.


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## Angelic123 (29 Nov 2009)

Do you  mind me asking how much your replumb cost?


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