Improving shower performance

[Roger Mills]

In my main home I have two power showers - one in the bathroom and one in the en-suite - both of which are gravity fed with low pressure stored hot and cold water, and boost the pressure with a pump. They both work fine.

In my holiday flat, I have an unvented hot cylinder, so both hot and cold water are effectively at mains pressure (but subject to a PRV which limits the pressure to about 3 bar). This hot and cold water is fed to a bar mixer shower, but the performance is nowhere near as good as my boosted gravity showers at home. What are the options for using a booster pump to improve the performance? I guess that you're not officially supposed to do that with a mains system, but would it work in practice?

I guess that if I were to measure the flow rate with the shower head removed, that would tell me how much water the mains could deliver. I would expect the flow rate to be a lot lower with the head fitted because of the resistance that it provides. So, if I boosted the pressure to provide the same flow rate with the head fitted as the mains provides without the head, I wouldn't actually be trying to "suck" water out of the mains.

Does that sound reasonable? Anyone ever done it?

[spuorgelgoog]

It may be a flow problem rather than pressure, but you could try adjusting the pressure up a bit if your valve is an adjustable one.

Owain

[dennis]

If you have 3 bar then there is a fault or you have an eco restrictor fitted.

If you fit a pump after the tank you may well cause it to collapse if you suck too much.

[The Natural Philosopher]

Sounds like bollocks. I have never got better shower performance than my mains pressure setups

maybe 3 bar is a pathetic pressure to limit at.

[GB]

Something's wrong IF it's really 3 bars when water is flowing. But the OP said it's limited to 3 bars and may be much less.

Maybe not. An unvented cylinder will be much stronger than the normal copper cylinder, and it will have an air pocket inside. The risk might be rupturing that? THere are also pressure relief valves, but I imagine they only deal with over-pressure.

[newshound]

I'd vote for the eco-restrictor. 3 bar should be fine.

[Brian Gaff]

Yes indeed and also mains pressure does vary both in the short and long term, so don't expect a one time measurement to be always what is going to happen. Sounds a bit odd to me that this shower is weedy, considering the pressure. Brian

[tabbypurr]

3 bar's plenty of pressure. Find the problem/restriction instead.

NT

[John Rumm]

Have you checked what the actual pressure into the system is? (it may be limited to 3 bar by the PRV, but that is not going to help if you have less than that to start with)?

Next have you checked the flow rate of the cold main?

If both those are ok, then I would suspect the mixer or shower hose/head.

There are a few mains pumping systems about - they have to have interlocks to stop them pumping should the input pressure fall too far.

However if you genuinely have a usable 3 bar and flow rate, you should be able to get a very decent shower without.

I would do it at the best cold tape first. The repeat at the shower.

Just fitting a shower head with less flow restriction may do what you want.

[Roger Mills]

Not recently. I did check the static mains pressure at an outside hose tap a while ago and - from memory - think that was about 4 bar. But that's at ground level and my flat's at first floor level, so that will make a *bit* of difference.

That's something I obviously need to do - and am planning to do - but I'm not at the flat at the moment.

It was a new mixer etc. which I installed when I bought the flat about 5 years ago, and it's never been very good. I've tried several shower heads - none of which made any significant difference. The best one was the one from my en-suite at my main home - but still not as good as it is at home.

Indeed. I'm going to have to measure both flow rates and pressure here at my main home, and at the flat, in order to work out what's going on.

Thanks for your comments - and to everyone else who has replied.

[tabbypurr]

FWIW I've had metal lumps partially block showers more than once. Why there are loose metal lumps to begin with I don't know :)

NT

[GB]

About a third of a bar IIRC. :)

[John Rumm]

IME (which to be fair is limited - I have only done two or three bar mixers) I have found the bar mixers are ok, but not as good as the more traditional mixer valves. I put one in the top bathroom of the loft conversion I did in the previous place. Water was about 3 bar and heated by a combi, so at best you have about 15 lpm of water available. The bar mixer was "ok" (certainly better than any electric shower), but not as good as the Mira 88 on the bathroom a floor below.

I also fitted a bar mixer on an Aunt's place that had a 24kW combi, and that again gave more than adequate results at around 8 lpm, but that might seem a bit tame if you are used to pumped showers doing 15 lpm or more.

I have a concealed mixer[1] on my shower here, and that is fed from an unvented cylinder (with the PRV set at 3.5 bar) - it takes its cold from the PRV balanced output outlet. That gives a very very good shower - right into the "flay the skin off you" territory if that's what floats your boat! So with adequate mains supply (large bore MDPE pipe here that will deliver 30 lpm at 5 to 6 bar) you can certainly get good showers from an unvented system.

[1] this one:

At least with bar mixers its usually easy to swap one for another, so if it is the valve that's the limitation, it not much upheaval to try another. (in fact you could just buy another to try, and ebay it if no better!)

[Capitol]

Agreed, I reckon it's the bar mixer. Is it thermostatic?

[Roger Mills]

It shouldn't be too difficult to assess the effect of the mixer. The shower is over the bath, at the opposite end to the taps, and shares the hot and cold supplies which divide under the bath. So I can compare the flow at the taps with that at the mixer fairly easily to see how much the mixer reduces it.

[Roger Mills]

Yes, it is thermostatic.