So I’m STILL having issues with one of our showers… The flow out the shower head is a dribble…
But another shower on the same floor is fine… Both are fed by a gravity/hot tank system (the other side of the house is a combi, and is fine)
Sooooo…what I’ve done is :
Replace the water shut off valves that side of the house as they were aged and wouldn’t turn off
Used NEW working valves to shut off the hot and cold water.
Removed the shower in question, leaving just the 15mm pipe sticking out the wall.

Now this is the odd bit… When I turn the water valves back on, the water FLIES out of the wall…
I’ve measured the flow at 12L/Min. Not amazing, but not terrible.
Of course, flow does not equal pressure… but…

I thought the issue may be the shower has a diverted (to a rain head, or standard head) so swapped it with a single head unit. Same issue.

The only other cheap option is to try a simply, NO THERMOSTAT shower mixer.. Wickes has one for 60 quid, but oddly it’s vastly different fixings, so isn’t jsut a case of swapping.

Will this make a difference?? Can a thermostat component choke the flow a lot?

We’re getting quotes for a combi to be fitted but really wanna save this as a last resort.

I just can’t for the life of me figure why this ONE shower is crap!
The taps and bath in the same bathroom work fine!!!!

Thoughts on a postcard!

DrP

So that’s 5 seconds to discharge 1 litre of water. Doesn’t sound much of a flow to me. But then I’m not a plumber….🤔

I presume you’ve checked the inline input filters and every nook and cranny for a blockage?
Our shower had a chunk of plaster in when we moved in, caught by the wee filter. I think previous owners had dribbly showers for years…

If it’s a thermostatic shower, you can change the cartridge. Remove it and take it to the plumbers merchants unless you can identify the shower model

Are you sure you’ve got the hot and cold the right way round (according to the thermostatic mixer.) If you’ve got the hot going into the cold, it will keep restricting the flow.

12l per min on each connection?

My money is on one of those little gauze filters somewhere being clogged up. Have you tried swapping the shower hose/head between the 2 showers?

When I fitted my shower it had a flow restrictor in it, something to do with WRAS Regs – have you checked you don’t have one? It was just a small disc with a reduced size hole in it.

Also I think you can get showers for either high pressure (combi) systems or low pressure (gravity fed) systems.

I think I’d look at fitting a pump before ripping another shower out though.

We had a similar situation. I took the non-return valves out and voila! It was fine.

BUT one thing we had to do when we turned the shower off was to set the temp as low as the mixer would go otherwise we ended up with a cold tank full of hot water!

Filters clean…
Non return valves removed….
No blockage….
Tried new mixer unit….

Ffs!

And 12l/min from EACH pipe

DrP

You’re on the south coast aren’t you? Have you tried a descaler – even if limescale isn’t actually blocking anything it might be stopping the thermostat from working properly.

Is the shower rated for low pressure, especially the shower head?
Fit the shower, remove the shower head so it is just discharging out of the pipe.
That will eliminate either the valve or the head.

BUT one thing we had to do when we turned the shower off was to set the temp as low as the mixer would go otherwise we ended up with a cold tank full of hot water!

…and then we all got Legionnaires’ disease? 😬

You’re on the south coast aren’t you? Have you tried a descaler – even if limescale isn’t actually blocking anything it might be stopping the thermostat from working properly.

I’ve fitted a NEW shower mixer unit…

It seems the flow out the wall is OK (it will jet across the shower cubicle and hit the glass door) but as soon as a mixer unit is fitted it’s a meek dribble

DrP

Is your cold pressure coming out of the wall significantly higher than your hot pressure? I found that balancing both improved overall output.

There’ll be a flow restrictor in the new unit. Could be that.

I found that balancing both improved overall output.

Indeed – we have a balancing valve hidden under the bath, as the old boiler was so crap a flow compared to the water pressure. You can manually do it, but this valve just works.

https://www.bes.co.uk/water-pressure-equalising-valve-16711/

Remove it and take it to the plumbers merchants

Please don’t do this. There’s quite literally thousands of showers on the market and every company uses umpteen different types of cartridge. They can even change cartridges on a production run so externally it’ll look the same but one won’t fit the other. You’ll just get asked for make/model and sent on your way.

Might be that the new unit isn’t suited for gravity fed systems.

Thermostatic valves do need replaced from time to time. I tried cleaning one without success. Replaced it instead and the flow which had been dropping off slowly over the years before it fell off a cliff, went back to the previous performance.

I’d checked part number for the shower on-line and got a lot of prices. Weirdly though the next price was from the supplier who I had phoned to check something. They were 50% less than anyone else, so I bought 2 to have a spare for next time

As I understand it, as it ages, it lets less hot water through, so to keep temp constant, it lets through less cold water too. If it is the valve and you try only running cold water, the pressure should be fine

(whispers…) I don’t think most people are reading my posts are they…?!!(/whispers)

DrP

oops…

(whispers…) I don’t think most people are reading my posts are they…?!!(/whispers)

DrP

Are you new here?

🤣🤣🤣🤣🤷‍♂️🤷‍♂️🤷‍♂️🤦‍♂️

I can see people mean well, so thank you!

Drp

It’s ok.

You’re saving the planet by having a low volume dribbly shower.

And saving the economy by purchasing a shower you didn’t need.

Win win!

Our Crosswater unit has a small flat head valve on both inlets. The one page instruction manual does not mention them. They were not fully open when we fitted it. Does yours have some?
They are not the quarter turn valves I’m used to. Also face outwards so you need holes in the tiles to adjust them when fitted.

Ok
So you know you have flow and pressure pre bar mixer right.
Next step, check flow rate out the mixer bar witj the flexi hose disconnected. Check at cold, warm and hot in lpm, about 6 to 8 is normal.
That passes now connect the flexi hose and disconnect the shower head. Repeat the flow rate test.
If it passes that, then screw on the head, check flows on cold, middle and hot.
Then go and drop £900 on a digi Aqualisa shower and salamander booster pump.

Rob – flow out the mixer bar with nothing attached is rubbish…

I really think the thermostatic valve (old, new, borrowed, or blue) is killing the flow..

Might try to find one that simply mixes the 2 water inlets – no thermostat control, just ‘flow alteration’..

DrP

I think I’ve read all your posts but I don’t see a response to what BigJohn asked:

Are you sure you’ve got the hot and cold the right way round

Are you sure you’ve got the hot and cold the right way round

oh, yeah i do….

DrP

How much pressure head have you actually got, distance from shower head height to cold water tank water level?
I’d put in a pumped unit. Either all in one power shower*, or dual pump stashed somewhere.

(* Was quite impressed with one of these at a recent holiday cottage. At home have mains pressure hot water system for brilliant showers)

Anyway, non thermostatic mixers are hateful things, never quite the right temp, and when anyone else in the house draws hot water from the same system….brrrrr.

What is the specification of the shower it will have a minimum pressure somewhere.

We had this problem as our water pressure was not enough to suit the thermostatic mixer.
Taps and flow seemed fine, but I changed the shower mixer to a non thermo one and problem solved.