Low water pressure

9
Found 17th May
Hi All

I have had a new shower one the first floor and some body jets but the pressure is terrable on both the cold and hot so I assume its a mains pressure issue.

I have a vaillant combi boiler.

whats my options to boost the prssure?

Would upping to a 42kw boiler help at all?
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9 Comments
You probably need a bigger boiler if your relying on it to heat the water, something specifically for a house with multiple showers and lots of rads.
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A higher capacity boiler is pointless. Suggesting 42kw is counter-intuitive, at that rate you would get around 17l of hot water a minute, but as you have very little in pressure from mains you by sounds of it wouldn't get 17l a minute anyhow. Plus boiler rated at 42kw would be less efficient and overall cost more with absolutely zero gain.

To start it would depend on what shower you have had fitted, power, electric, mixer etc as that helps. Also what is pressure like from your taps upstairs. Was your shower professionally fitted, ask as we just had quote for new bathroom and guy measured our flow rate from out basin and bath and shower to gauge best fixtures and fittings.

Our flow rate from mains is high at 18l a minute, our current boiler only rated for 13l so for us at full pressure in shower and taps boiler couldn't produce enough hot water so opposite issue for us was to reduce pipe size until new bathroom fitted.

There are few options available, for a start you should find out your mains flow rate, if its too low then water board can help somewhat if below there minimum standards. A pump as mentioned above is another alternative.

If you had no issues with old shower before replaced then speak to person who installed it.

And oversizing boiler capacity has no effect on radiators at all, a radiator can only give out its rated heat no matter how big your boiler is but a bigger boiler will use more gas to give out same heat but it can also hinder issues with central heating as its flow rate means heat wont dissipate quick enough, so you find you use more gas just to heat up all your rads and in turn boiler will cycle on an off, come winter you'll notice it takes longer for your home to heat up.

Highest KW for any house upto large 4 bedroom with bathroom/shower is around 28kw. If water pressure and flow rate sufficient then stepping upto 30kw is advantageous. If you need 42kw you really should have secondary system installed for hotwater and bathrooms, with combi useful just for kitchen/WC
If you have a big rain shower head and jets then you're probably lowering the water pressure too much. Combi boilers only work on mains pressure so I doubt they will stand up to a power shower demand. My Mum had to have a pump and cylinder installed to boost her pressure but obvious costs involved and I would say a combi isn't suitable.

I would probably look at a pressure reducing shower head and see if that works.
There's a lot of misinformation here.

You can not pump mains water (you can fit a small booster). Talk of what shower you have is immaterial, it must be a mixer (and usually thermostatic).

Firstly get a proper plumber. He will need to check standing/working pressure and flow rates at the stop tap, and at the shower. This will tell you where the problem is, and what the problem is.

Check the minimum pressure and flow rate requirements of the shower.

A larger boiler output will be useless if the mains can not supply adequate pressure/flow.
Could it be the main valve/under kitchen sink valve has not been opened fully?
We had a similar problem. The plumber fitted a pump and now its sorted
getting a bigger boiler is pointless and would be a waste of money. get a plumber in to check flow rates etc
Hi All

Its a mixer shower and think I have found the issue. The rain water type shower head is too large and needs 3 bar pressure and so do the body jets.


I purchased these for the plumber to fit so is my fault.

I changed the shower head and it has doubled the flow and I have ordered smaller water jets.

Pressure at the house tested at 1.5 bar. Anglian water set at 1 bar.

Thanks all.
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