low pressure

Postby gsk » Thu Mar 26, 2009 7:25 pm


i have new combi valliant boiler fitted, but the main water pressure is very low during day. How can i increase this?

Also, looking to fit a shower, with hardly any pressure coming through mains. What would be my best solution to overcome this?

Before combi boiler i had a water supply via tank in loft into emersion heater where water pressure was good/high for decent showe, but has now all been taken off.

Hope you can help.
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Joined: Thu Mar 26, 2009 7:12 pm


Simply Build It

Postby rosebery » Fri Mar 27, 2009 7:56 am

First you must determine if this is your problem or the water company's problem.

Have you an outside tap or a washing machine? If so beg, borrow or ..... a pressure gauge and check the mains pressure at various times of the day.

Do your neighbours have the same problem? That should clarify your pressure issue and whether it fluctuates. Did your combi installer chack your incoming pressure before a) quoting and b) installing?

Second I it's possible you don't have a pressure problem at all but a flow rate problem. What is the flow rate of your combi boiler for DHW? Was it properly sized for your installation?

Third and I'm sorry for repeating myself but I AM going to keep saying this until I'm blue in the face:

"I had a new combi boiler fitted and now I'm not satisfied" = GET THE INSTALLER BACK TO LOOK AT IT.

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Postby gsk » Fri Mar 27, 2009 6:17 pm

Thanks for a quick responce.

I have had the boiler checked and it is ok, in term of pressure.
We also have a slow flow from direct cold mains, which increases around 9-10pm, but then slows down again in the morning around 6am. This is also the case with the neighbourhood.

I have heard that it is the local authority who are decreasing the pressure during the day, but my problem is that i cannot have a decent pressure from shower.

What do you advice?

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Joined: Thu Mar 26, 2009 7:12 pm

Postby plumbbob » Sat Mar 28, 2009 9:23 pm

It is not unknown for water supply companies to lower the pressure during the day to save water.

Contact them and ask them to test your supply. If more than one house is effected, they might increase the mains pressure. Be persuasive.

Of course, the trouble may be with your own individual supply. It may be furred up or even burst. Iron is the worst for a reduced bore as the corrosion and limescale build up and block the pipe.

I should say though, your boiler installer should have identified the potential problem before installing the Vaillant and offered advice.

Nice choice of boiler though. Do like Vaillant.
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Joined: Wed May 07, 2008 9:59 pm

Postby rosebery » Sun Mar 29, 2009 11:53 am

"What do you advice"

1. Discuss the problem with the water company; and

2. Discuss the problem with your installer.

and don't be browbeaten by either of them.

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Joined: Wed Sep 26, 2007 8:55 pm

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