Thermostatic shower valve

[Eric'n'Ernie]

I've got a shower mixer all plumbed in, dedicated feeds to H&C inlets via a flow switched pump.

There's a tiny ooze of water emerging from the outlet on top of the mixer whether the pump fuse is in or not.

When I disconnect the h&c feeds I've got a good flow from each, even with the pump off. With the pump on I've got oodles of water.

It seems the mixer valve is restricting the flow to practically nothing - however, if I undo the h or c feed into the valve, and thus cause the pump to kick in, then reconnect the feed pipe, this delivers the water through the shower and out of the head without difficulty.

I'm clearly missing something? Can anyone help?

 

[ChrisR]

What mixer is it?
Some (eg Mira) have two outlets and you have to open the one you want to use.

CHecked for blocked filters?

 

[Eric'n'Ernie]

It's a Hudson Reed Tec mixer valve, no diverter. It's got inlets for h&c and an outlet.

I didn't check for blockages, as it flows fine once the pump is kicking the water through it. It just isn't allowing enough flow when I open the valve to trip the pump's flow switch.

How does the thermostat affect the flow? Could it be that?

 

[Eric'n'Ernie]

Am I asking a dumb question? I guess so....

15mm pipe? Could it be that I need 22mm?

 

[dal5band]

As you say there is a flow restriction of some sort that won't allow the low pressure water to flow at all. Normally if you turn the shower valve to the cold end it opens for a good flow.

- Some sort of one way device - check valve built into the inlets of the shower valve
- the inlet filters themselves.
- some vlaves come with restricters for mains use. Just discs with a smaller bore - check these are out.
- Some people have reported getting the shower pump to kick in by opening and shutting another tap near by to cause a pressure wave.
- try taking the shower head off to see if that's the problem
- could be the shower valve has a lower pressure limit.

 

[Eric'n'Ernie]

As you say there is a flow restriction of some sort that won't allow the low pressure water to flow at all. Normally if you turn the shower valve to the cold end it opens for a good flow.

- Some sort of one way device - check valve built into the inlets of the shower valve
- the inlet filters themselves.
- some vlaves come with restricters for mains use. Just discs with a smaller bore - check these are out.
- Some people have reported getting the shower pump to kick in by opening and shutting another tap near by to cause a pressure wave.
- try taking the shower head off to see if that's the problem
- could be the shower valve has a lower pressure limit.

Thanks a lot for your time and input;

1) Sorry - I wouldn't know what to look for!
2) Inlet filters - I haven't checked as I assumed that the fact that water flows once the pump does kick in means that they're clear.
3) I could check that with the manufacturer I guess. (I have mailed them but no joy yet)
4) I've put a dedicated feed in, so shouldn't have any effect (?).
5) I've stripped the shower head and pipe off the shower mixer, the little ooze of water is coming directly out of the top of the mixer.
6) The shower MI's suggest a minimum 0.1bar in order to work. I guess if that isn't being exceeded, I won't get enough flow - but it looks a fair flow to me.

How much water comes out of a 15mm pipe at 0.1 bar in 1 minute!?

How do you work that out? Any mathematicians out there? I could take the fuse out of the pump, take the feeds off the mixer and measure the flow rate. Are there tables of that sort of data available?

Thanks for any help.

 

[Breesey]

How do you work that out? Any mathematicians out there? I could take the fuse out of the pump, take the feeds off the mixer and measure the flow rate. Are there tables of that sort of data available?

Thanks for any help.

Flow rate depends on several factors so flow rate is not a constant relative to bore and pressure etc.

Easiest thing to do is run the pipe for 10 seconds into a bucket, measure how much you have and multiply it by 6. Or you might have a flow wier handy!!

 

[lagunaglen]

Does the pipework go up into the loft before connecting down to the mixer valve, it could be getting air locked if thats the case and disconnecting pipe work releases the air lock , you may need to fit air vents at highest point if this is the case.

 

[Eric'n'Ernie]

How do you work that out? Any mathematicians out there? I could take the fuse out of the pump, take the feeds off the mixer and measure the flow rate. Are there tables of that sort of data available?

Thanks for any help.

Flow rate depends on several factors so flow rate is not a constant relative to bore and pressure etc.

Easiest thing to do is run the pipe for 10 seconds into a bucket, measure how much you have and multiply it by 6. Or you might have a flow wier handy!!

Hmm. Ok. No flow wier (!) though.

 

[Eric'n'Ernie]

Does the pipework go up into the loft before connecting down to the mixer valve, it could be getting air locked if thats the case and disconnecting pipe work releases the air lock , you may need to fit air vents at highest point if this is the case.

Inlet pipes, come from the loft, where they go horizontally and then down to the pump in the airing cupboard.

Equal pressure in theory from cistern in loft feeding both. (dedicated feed).

There seems planty of pressure out of the pipes when i disconnect them from the shower mixer though...

Thanks for your reply.