Shower pump problem

[Gilesda]

Is that how you start/run the shower usually? A true test would do it at the height that the shower is normally is at with the shower head on, that gives you an accurate representation of L/Min in normal use

Your hot water supply is the problem here, the thermo valve when opened starts with mostly hot to first and then starts to add cold as the hot supply heats up until up to temp. If there isn't enough flow at that point, from the shower head, then it won't start the pump.

The only thing that's changed here is the shower itself, so that's where your problem lies. If you had a bar mixer before chances are it was a thermo too but we'll never know. No or faulty NRV's can allow the pump to drain back to the cylinder when another hot outlet is opened but they can restrict the flow a little too as @steve32 mentions, removing them may allow the flow to increase enough but could also exacerbate the air issue in the hot supply, which is what you are suffering from.

If you can try this test too. Turn off the power to the pump, turn on the shower, turn the pump back on, does it run and keep running?

I take your point about measuring the water flow out of the head and not the bottom of the valve but the shower doesn't work if I drop the shower head into the bath. It was just easier to do out of the valve.

If I set the shower away without the pump running nothing comes out of the valve in its centre temp position. Unless I bleed the pipes in the loft then it does. Then if I turn the pump on it runs ok. Leave it a short while though and it doesn't work.

I slackened the nuts on the back of the valve with the pump on and obviously water came out of them and then the the pump started. So I tightened the nuts up and the shower worked fine on all temperatures. Left it 5 minutes and it would only start on full cold. I know that if I then left it say overnight it wouldn't work at all without the bleeding to get it flowing.

I've got a 22mm one way valve but I haven't fitted it. It will be a bit of hassle and salamander only show a NRV when the pump is above the shower head height. Do you think it will make a difference if I fit it just above the hot outlet?

Was in B&Q today and they were selling of loads of taps and showers. I bought a basic single lever valve for only £15 and fitted that. It works perfectly however long I leave it and it doesn't need any bleeding. When I first switched it on it sputtered a bit and that was it. It looks sh*t, it looks like a single lever kitchen tap sticking out the wall but at least it operates the pump. I haven't given up with the other shower but at least I can fit that knowing I won't get grief off the wife when she can't have a shower.

I've still got the previous bar mixer, how can I tell if it's thermostatic? It has a button on the temperature knob that you have to depress to go past a certain temperature but I don't know if it's thermostatic or not.

 

[Gilesda]

Have you tried removing the non return valves in the shower valve.

I'm going to try and remove them when I get a minute. The cheapo valve I've just fitted has them and it works without problems but it isn't thermostatic.

 

[jeff the gasman]

Negative head pump f. f. s

 

[Madrab]

Negative head pump f. f. s

Ultimately the easiest solution and would agree but seems a pretty expensive fix when the issue seems to be just fixing the lack of flow especially if it worked fine prior to the change to a new mixer.

OP .... hot flow's obviously the issue then if it works fine with another manual outlet. You previous will be thermostatic by the sounds of it but must have had less resistance. Try the NRV removal as @steve32 mentions and see what happens but may just be the waterways/cartridge where the restriction is.

 

[Gilesda]

Ultimately the easiest solution and would agree but seems a pretty expensive fix when the issue seems to be just fixing the lack of flow especially if it worked fine prior to the change to a new mixer.

OP .... hot flow's obviously the issue then if it works fine with another manual outlet. You previous will be thermostatic by the sounds of it but must have had less resistance. Try the NRV removal as @steve32 mentions and see what happens but may just be the waterways/cartridge where the restriction is.

The strange thing is if I open the bleed nipples in the loft with the pump off the hot comes out in a little jet. The cold just bubbles over the top of the nipple.
I'll remove the non returns from the valve tomorrow and see if that works. Thanks for all the help it's appreciated.

 

[Gilesda]

Negative head pump f. f. s

I looked at that possibility but in the next year or so I'm going to get a combi or a unvented system fitted. The mixer valve I bought will still be useable but the pump won't. They're a bit expensive to only use for a year or two.

 

[Gilesda]

Well talk about sods law.
I've left the non thermostatic valve for about 3 hours, went to try it again, put it in a central position and the pump didn't start. There was a reasonable amount of water coming out of the shower head without the pump but not enough for a decent shower. I moved the lever to full hot and the pump kicked in. Full cold the same but it doesn't work set in the middle. I'm stumped now.

 

[Madrab]

Flow - both in the middle doesn't give enough flow past either flow switch, set to full cold or hot increases the flow to either side activating the switch, pump kicks in.

Did you try the - switch pump off at the mains, turn on shower, turn pump mains back on, does it then start and run?

 

[Gilesda]

Flow - both in the middle doesn't give enough flow past either flow switch, set to full cold or hot increases the flow to either side activating the switch, pump kicks in.

Did you try the - switch pump off at the mains, turn on shower, turn pump mains back on, does it then start and run?

When I had the thermostatic mixer fitted if I turned on the shower with the pump switched off nothing came out of the shower head. That's with the temperature set in the middle.
If I switched on the pump and bled the pipes in the loft the pump kicked in and the shower worked. There was just a tiny bit of air came out of the bleed nipples but I had to let the nipples release a canny bit of water before the pump worked.

I've just tried that with this non thermostatic valve and water came out of the shower head this time. That's with the pump off and the valve lever in the centre position.
I then switched on the pump and nothing happened, the pump didn't work.
I measured the flow out of the shower head with no pump and in 30 seconds it put out 750ml. So that's 1.5 litres a minute.

 

[dilalio]

Service/replace the flow switches on the pump. There's an Irish guy on the Internet, youtube who's very good with shower pumps and has detailed videos on their repair/maintenance... I've spoken to him about an intermittent pump problem for a customer and he was very helpful.

 

[Madrab]

I measured the flow out of the shower head with no pump and in 30 seconds it put out 750ml. So that's 1.5 litres a minute.

If there's only 1.5L/min then you're not getting enough flow to activate the switches. The CT50 needs a min of 2L/Min mixed to activate the pump. So it's either sort the flow/shower out or as @jeff the gasman mentioned you're looking at changing the pump.

If you take the shower off and just run the open pipe (with the pump off) do you get more than 2L/Min?

If it was me I'd be making up a little test jig to fit the shower outlets - 2 pieces of pipe with 3/4" ends connected to the outlets and then branch together with a full bore valve on the end and see what happens with that. If you get more than 2L/Min and the pump then runs in that scenario then you know its the shower(s) at fault

 

[Gilesda]

If there's only 1.5L/min then you're not getting enough flow to activate the switches. The CT50 needs a min of 2L/Min mixed to activate the pump. So it's either sort the flow/shower out or as @jeff the gasman mentioned you're looking at changing the pump.

If you take the shower off and just run the open pipe (with the pump off) do you get more than 2L/Min?

If it was me I'd be making up a little test jig to fit the shower outlets - 2 pieces of pipe with 3/4" ends connected to the outlets and then branch together with a full bore valve on the end and see what happens with that. If you get more than 2L/Min and the pump then runs in that scenario then you know its the shower(s) at fault

This new basic mixer I've fitted is working ok though not perfectly.
It's pulsed on and off a few times while not in use. It was doing that earlier and continuously so I bled the pipes and it stopped. It also wont start the pump when the temp is set in the middle, though there is water coming out of the shower head unlike the thermostatic bar mixer. If I drop the shower head into the bath it will activate the pump in any position.

When you say take the head off and check if there is more than 2l a minute do you mean with the hose held up at the shower head height? I'll try that when I get home.

I'll see if I can knock up the test rig as well.

 

[dilalio]

Don't forget that you probably need 2l/pm on each flow switch (hot and cold) to get them started. If you've got 2l/pm with 50/50 hot/cold thermo setting then that has to be divided (by whatever ratio it mixes within) which may not be enough to trigger one or both flow switches.

As per @Madrab, I'd be testing with a jig and I'd also look at getting rid of those compression elbows on the hot supply and replacing with pulled bends. I'd also try and get the pump on the floor next to the cylinder and/or raising the cwt. Other than that it would be a neg head pump. Please also check that your shower outlets don't have any water saving inserts installed

 

[Gilesda]

This basic single lever mixer I've fitted is now working great so I'm just going to stick with this for now. After bleeding the pipes and a couple of uses it operates the pump in any position of the temperature range and does it even after leaving it for almost 24 hours. There obviously is enough flow through the pipes otherwise this valve wouldn't operate the pump. The thermostatic bar that didn't work very well must have too many restrictions on the flow to work with the head of water and setup I have.
Thanks for all inputs, it was much appreciated.

 

[Madrab]

The thermostatic bar that didn't work very well must have too many restrictions on the flow to work with the head of water and setup I have.

Yup