Low pressure thermostatic shower

[19nffc77]

Hi all,

I have just moved into a new house which has this shower mixer:

When I turn it on water doesn't get much more than a dribble, I have removed the shower head to see if it is clogged but the flow remains the same. I have tried contacting the previous owner to ask if there is a pump anywhere that might be switched off but get no answer so is there any way I can find out if one is fitted? Likely places there might be one etc or is there any other ways a layman can fault find the issue?

 

[oldbutnotdead]

What is the hot water supply- is it gas or oil combi boiler (so boiler fires when you run a hot tap) or is there a hot water cylinder? If there is a cylinder, look near there for a shower pump.
Or look outside the bathroom - any mystery switches high on the walls?
How well does cold flow? What is hot and cold flow like in the rest of the house?

 

[19nffc77]

Sorry for the late reply, the previous owner has been in touch and said that the shower is gravity fed and it has always been like this as that’s how he preferred it. Not sure I believe it as it’s so weak. The taps in the sink are stronger as are the taps in the main bathroom bath and sink, albeit they are not too strong either. The boiler has a tank in an airing cupboard, boiler and tank are very old.

 

[oldbutnotdead]

When you say 'a dribble', how many litres/minute is it delivering? Compare that with the litres/min from the sink or the bath taps.
The shower on a gravity system will usually deliver the lowest pressure cos it's the highest appliance, might only be a metre or 2 of head.
If there's no massive difference (20% plus) between sink delivery and shower delivery then it is what it is. There are options to improve a gravity system, do those measurements first. Hot l/min, cold l/min, usable temperature l/min.

 

[19nffc77]

So I just measured the amount of water I get from the shower and the sink in the ensuite and it is as follows:

Shower hot - 1.5l/min
Shower cold - 4 l/min
Sink hot - 4 l/min
Sink cold - 8.5 l/min

So because its about double the amount of water delivered to the shower compared to the sink does that mean that there is an issue somewhere?

 

[oldbutnotdead]

Yeah that's not exactly superb is it.
Do you know if the cold comes from the tank or is it direct from the mains?
Reason for asking- it is possible that yon shower mixer is designed for high pressure (mains fed) applications and has double-check valves in the pipes- if both feeds come from the tank then you can ditch those valves which will improve the flow significantly.
The other possibility is cheap smallbore isolation valves in the pipe runs to the shower (they should be somewhere accessible, have a look around)

 

[19nffc77]

Even more pathetic than I’d imagined tbh. That info is great though thanks I’ll have a look around.

 

[Madrab]

A thermostatic shower will always struggle with gravity fed supplies. It's very design (narrow restricted waterways within the shower and a thermo cartridge to push through) really needs mains or pumped supplies to work effectively.

Your basin taps will flow more, probably due to the fact that they will probably be full flow taps with very little in the way of restrictions and possibly fed by 22mm pipework from the attic cistern, if the cold isn't, as suggested, unbalanced and fed from the mains.

 

[19nffc77]

One other thing that we are doing is replacing the boiler as it's really old and not very effective. I was thinking of switching to a combination boiler, am I right in thinking that if I do it will negate the need for the hot water tank in the airing cupboard and cold water tank in the loft? If so will this improve flow rate or will I still need the pump?

 

[oldbutnotdead]

Before you think about a combi boiler, check the mains water supply to your house (litres/min and ideally dynamic pressure). Use the cold tap nearest the stopcock, make sure it is fed from the main not a tank.
With your current setup (hot water cylinder) you have options for fitting shower pumps. If you fit a combi that option goes away so you'll be limited to whatever the mains delivers.

 

[19nffc77]

The tap is fed from the mains and it’s about 15 l/min but the tap has an aerator on it so presumably it would be a bit more? I’m just an average diyer so don’t think I can measure the pressure.

 

[oldbutnotdead]

Your local water supplier can check flow and dynamic pressure for you at their stoptap (the one on the street)- that'll tell you the best it will ever get. If you get to the stage of talking to companies about boilers they should have the gear to measure it. 15 l/min is adequate for a single bathroom through a combi, you may have to change some of the internal pipework to feel any benefit though

 

[ericmark]

I look at the difference shower cold to shower hot, normally one feeds the shower from the header tank cold water, so both at same pressure. Had that been done, you could get a power shower where the pump is in the shower controls.

Head is the problem, I know my parents had very little head, and used an electric instant shower upstairs, as the head was so bad, and a power shower down stairs in the wet room, my dad tripped the shower RCD and my mother did not realise anything was wrong with down stairs shower, the output was reduced without motor running, but still worked fine.

The power shower looked like an electric instant shower, about same size, but only needed a 3 amp feed not 40 amp, but not allowed direct connection to incoming main. When the water tank started to leak, my dad had a combi boiler fitted and completely new central heating, and we had to get them back to change the illegal power shower for a mixer shower. The latter was no where near as good.

 

[Madrab]

The long and the short of it is, if you want to use more than one hot outlet at a time them don't go with a combi, even then you want to confirm the mains dynamic pressure and flow is suitable to supply multiple outlets at once before you commit to a combi.