Options to increase bath tap hot water pressure

[DrF]

I've recently moved into a house without a shower. The hot water pressure out of the bath top is too low to effectively use one of those hand-hold shower heads that attaches to the tap. I will probably discuss with the landlord at some point the possibility of getting a shower fitted, but this may be impractical given the layout of the bathroom - low sloping roof at one end of the bath and a Victorian sash window at the other. I was wondering whether there are any practical options for increasing the water pressure of the tap so a hand held shower becomes practical.

The pressure is low because the hot water tank is on the same level as the bath, would there be any practical options to fit a secondary hot water header tank above the current one for example?

TIA

[crossposted to cam.misc and uk.d-i-y, followups to uk.d-i-y]

[Dave Fawthrop]

|I've recently moved into a house without a shower. The hot water |pressure out of the bath top is too low to effectively use one of those |hand-hold shower heads that attaches to the tap. I will probably discuss |with the landlord at some point the possibility of getting a shower |fitted, but this may be impractical given the layout of the bathroom - |low sloping roof at one end of the bath and a Victorian sash window at |the other. I was wondering whether there are any practical options for |increasing the water pressure of the tap so a hand held shower becomes |practical. | |The pressure is low because the hot water tank is on the same level as |the bath, would there be any practical options to fit a secondary hot |water header tank above the current one for example?

Fit shower pump. One example is

a combi boiler ?

[Dave Baker]

The pressure to the tap has nothing to do with the location of the hot water tank, or immersion cylinder I presume you are referring to. It's the pressure from the cold water tank that feeds the hot water tank which determines this. The immersion tank could happily be below the bath provided the cold tank was above it.

-- Dave Baker Puma Race Engines

Camp USA engineer minces about for high performance specialist (4,4,7)

[John Rumm]

Where the hot water cylinder is does not matter. What matters is how far above the tap the cold water cistern that feeds it is.

A pump may be a simple solution, although those showers that fit onto the taps using rubber connectors are poor at very best. You may need a pump and to change the bath mixer taps for ones that have an integral shower.

[Roger]

The message from DrF contains these words:

One option is a venturi shower which would be simpler to install than a pump but probably not much cheaper. There are some cheap ones around that have a bad reputation but expensive ones can be good. The only one I have experience of and can therefore recommend is the Trevi Boost.

[The Medway Handyman]

The Aquamixer by Aqualisa is expensive but good.

[Dave Plowman (News)]

Assuming a low pressure system fed from a header tank in the loft, etc, it's the height of that above the taps that sets the pressure, not where the storage tank is. And if you have a normal roof void, it's often a fairly simple matter to raise that header tank and considerably increase the flow rate.

[James]

With a similar problem I fitted a pump, cost about =A3120, it works well although its a bit noisy.

I suspect raising the cold header tank would be at least as much hassle (although perhaps a bit cheaper and no electrics needed) and would not increase water pressure that much.

With the pump you do get quite a high pressure. Although this can mean a lot of hot water usage with a normal shower head, if you use a 'water saving' shower head (i.e. one with smaller holes) you can get a more powerful shower for the same (or even less) water usage, compared with a lower pressure shower e.g. from a raised header tank.

James

Dave Plowman (News) wrote:

[Dave Plowman (News)]

It can make a vast difference where the tank is sat on the ceiling of the bathroom.

[The Natural Philosopher]

Yes, but not that. Buy a pump.

[Al Grant]

You probably already have one, otherwise you'd have nothing to produce pressure to push the water out of the hot tank to the bath, would you? But even one floor's level of gravity pressure will struggle to compete against mains-pressure cold water. You have several options:

(a) install an instant electric shower (runs off cold but needs a separate high-amp electric circuit). I have done this myself, it's not that hard though the electric bit is probably illegal to DIY now. The flow is not great though.

(b) install a mixer shower with pumped hot supply. Once you have one of these you will never want to go back to (a). If you install it over a bath then you really need a proper watertight shower screen rather than a curtain.

(c) put a shower pump in the bath hot tap pipe (this would be odd, but I list it for completeness)

(d) replace the hot water tank with a combi boiler which would deliver hot water at mains pressure. Combi boilers are said to be economical for small households both in terms of space and in not having a tankful of hot water sitting around. I would suggest you ask your landlord about this.

[Dave Plowman (News)]

It will for pressure, probably, but the flow rate is entirely dependant on the resistance of the pipework, etc. And it's easy to beat the flow rate of most mains pressure 15mm pipes from a storage system.

[DrF]

Shows what I know! Don't quite understand how that is though as surely the pressure will drop as hot water comes out of the tank so there's not as large a head on it. I'm thinking this working on the assumption that the level of hot water in the tank does decrease, if it shouldn't due to adequate pressure from the cold tank then I stand corrected. However it appears that the pressure at the hot tap does decrease if it's been running for a while, could this be a symptom of a low pressure feeding the hot water tank?

[John Rumm]

No, the hot water comes out of the top of the hot water cylinder - hence it is always full. The cold water is fed into the bottom of the tank from the loft cistern.

You may find that you are emptying the loft tank faster than the rising main can restore it - hence the head will fall with time (not by much - the depth of the tank at most, but when you only have a few feet of head in the first place losing 12-18" can make a difference).

[Ed Sirett]

Or there may be some crud near the storage cistern outlet in he loft.

The OPs Landlord is obligated to fix this (Assuming the tenancy is a normal shorthold type), unless the fault was always there and you can still run a bath before it gets cold.

[DrF]

Ah. I've just been having another look at our tank since I thought cold water was going into the top of it as it certainly sounds like that when drawing hot water. It looks to me that cold water does indeed go in the top, but that the tank may be divided into two. It has a specification for a Feed Cistern, which I assume is the top part. The hot water does indeed seem to come out of the top of the lower part. It says 'Combination Tank' on it, which might be relevant. Could it be then that the flow rate into the Feed Cistern is low, causing the low hot water pressure, or is it worse than that - is the only pressure available to the hot tank that which is supplied by the head of water in the Feed Cistern, which is presumably always going to be low as it sits directly on top of the hot water cylinder.

We can certainly run a bath with plenty of hot water, it'd just be nice to have enough pressure to effectively use a hand held shower head in the bath.

Thanks again.

[John Rumm]

Indeed it is! The combination tank is in fact two tanks in one - a hot water cylinder with a cold cistern above it. Used to be popular in bungalows since they are easy to fit. The downside (as you have found out) is that the available head is about as small as it is physically possible to make it and have it still work!

Probably both. The maximum head will be very limited due to the proximity of the cistern to the cylinder. Also it is not uncomon for the mains feed to be unable to supply the cistern fast enough to cope with the demands of the hot and cold taps on the bath (which may drain the cold cistern at over 40 lpm combined). So as you run the bath, the water level in the cistern falls, which in this case may make a significant difference to the available pressure since your total head over the bath could be as little as 4 or 5'

In this circumstance you only really have two options - pump or venturi shower. Since you probably don't have mains cold water taken to the bath taps at the moment, a pump may work out simpler.

You may be able to improve the recovery rate of the cold cistern by fitting a second float valve - but this would only help if the limiting factor was the current valve restricting the refil rate and not the flow rate available from the cold main.

[Edward W. Thompson]

Had a similar problem. REmoved the bath tap and found a piece of 'foam' under. Emoved foam, now plenty of pressure/flow. Might be worth removing the tap to check.

[CWatters]

It's not the height of the HW tank that's the problem - it's the height of the header tank in the loft that feeds it. Can that be raised? That would make a small improvement. Otherwise you can add a shower pump between the tank and taps. Not likely to be cheap though. Pumps are £150 to £500 plus fitting. Choose one that produces a good flow rate not just a good pressure.

When they install a new shower it's best to run a new pipe all the way back to the tank rather than connect into the existing pipes feeding the bath or basin. To connect the pipe to the tank use a Surrey flange.

[The Natural Philosopher]

You got it in one

I had one of these once..absolutely no chance of ading a shwoer without a pump, as the top of the feed cistern was at ceiling height to the bathroom.

IOf all the plumbing I have ever encountered, this is the nastiest and cheapest.

You never will unless the tank and feed is a storey above the bathroom.