low pressure problem

[Dean Heighington]

Two small CWS tanks in loft connected to each other, rather than one large one. Cylinder on ground floor. Getting very poor flow from wall mounted bath filler mixer tap - Bristan brand, requires 1bar pressure combined from hot and cold feeds. About to measure that today and have sourced an alternative brand that only requires 1/2bar. Other than installing a pump (which would now mean ALL outlets in bathroom would be pumped) what else could I do to increase the head of pressure? Raise tanks in loft? About as much work/cost as installing a pump. Does a single tank provide more head than 2 connected smaller tanks?

Looking for options with changing the mixer being the simplest but still doesn't improve pressure.

Tia, Deano

[Bob Minchin]

Head of water is simply what it says. It will not be improved by the number of tanks. It is the vertical distance between the top of the water in the tank(s) and the point of delivery - your mixer.

1 bar is about 10 metre head. You wont get that by messing with tanks!

The sort of mixers you are looking at are designed for pressurized water systems not gravity feed that you have. Stick to either simple taps or a mixed specifically designed for gravity feed plumbing.

ps It does not matter where you cylinder is fitted.

Bob

[John Rumm]

You get a bar of pressure for every 30' of head approximately... So the trick to successful use of low pressure sources, is 22mm pipe, swept bends (ans as few as possible) and short runs - feeding taps etc designed for low pressure (many are not).

One tank will possibly provide a little more head - but quite possibly only a few inches. Raising it will not usually get you much pressure in absolute terms, but it might make a difference to an upstairs tap which, when you think about it, might only have 7' of head. You could potentially double that with careful tank positioning.

The other options are of course to go for mains pressure (or close to it) hot water systems. That means decent mains cold flow rate, and either a combi boiler, a heat bank, or an unvented cylinder.

Taps designed for low pressure will perform very much better than ones that are not. But they still depend on other aspects of the system being well implemented to reap the best rewards.

[Ret.]

You could always switch to a combi and completely remove the need for header tanks!

It seems to be a regular problem these days. Many taps on sale in the UK today are manufactured abroad where few countries have antiquated gravity feed systems. Consequently they do not work well with our system.

We had our kitchen facelifted some years ago and had a single lever mixer tap fitted. Cold supply, which was mains fed, was fine - but hot flow was abysmal. Two years ago we switched to a combi and now flow from both hot and cold is fine.

[Dean Heighington]

Thanks guys, pretty much what I expected. I am getting 1/2bar at each outlet which IIUC is the minimum required by the Bristan if the 1bar they specify is combined across the 2 feeds, and it's crap, so they should up this in their literature! The alternative is an Ultra brand tap that requires only 1/2bar and that IS combined (I asked this time). So I need to check if the centres between the tap inlets are the same as the existing first, or should I consider two separate wall mounted single taps? Anyone seem these anywhere?

I wish I was able to put a pump in but that's beyond the budget! And btw... Anyone want a Bristan wall mounted tap? Going cheap!!!

Thanks D

[polly filler]

you could also check the top & bottom connections of your cylinder, as these often get scaled up and restrict the flow to the taps

[Phil L]

Is there any reason why you can't get a new water main connected?

[Dean Heighington]

Yeah, that was crossing my mind at some point or even the whole cylinder scaled up cos the water at this local is notoriously hard, but the cylinder and boiler are fairly recent by the looks of things. I can only imagine bad pipe runs with lots of 90s cos draining the CWS and refilling resulted in air locks to both hot and cold feeds. The outlets from the CWS are 1" hot and 3/4" cold so something has been done downstream.

Low pressure mixer coming tomorrow and plumb counter are prepared to take back the Bristan because the pressure meets their min spec but does not perform well.

Will keep you posted :)

[Dean Heighington]

It's a gravity fed system. The rising main feed to the CWS tank is not an issue. Have you misunderstood? Or have I :)