Thermostatic Shower Cuts Out

[TomWhitson]

Hi,

We have a fairly low pressure gravity fed system (~1m head) and recently had a new thermostatic valve fitted. Since then the shower is acting quite strangely,

Sometimes takes 1+ minute for water to start flowing
Sometimes cuts out when changing temperature

Prior to having the new valve installed there were no issues other than a slightly weak shower. The previous valve was the one installed when the house was built ~ 12 years ago.

We've been advised a few different things, but no-one seems sure of the reason why this is occurring. Low pressure or a stuck check valve seem to be the main suggestions so I am wondering what the best solution might be.

Remove the check valves (we do not have a combi and have been advised this is the main reason)
Change to a manual (non thermostatic shower valve)
Install a pump to increase pressure
Install a combi-boiler to increase hot pressure (not sure this will increase pressure? Boiler is downstairs in the kitchen ~4m below shower head)

I appreciate any thoughts on it, this is driving me up the wall since no-one seems sure of why it's happening and how to resolve it. I would just like to get it resolved no matter what the solution!

Tom

 

[seco services]

And the shower make/model is ?

 

[TomWhitson]

Hi, thanks for the response..

It is this one,

http://www.victoriaplumb.com/Shower...aditional-Dual-Exposed-Bottom-Outlet_895.html

and installation guide is here,

http://www.victoriaplumb.com/images...raditional-Dual-Exposed-Bottom-Outlet_895.pdf

Only thing I can see is that the shower hose is attached to the top not the bottom, but according to the guide this seems to be ok.

We have a standard hot on the left cold on the right pipework, and turning the temperature knob to hot causes the shower to get hotter and vice versa so it looks installed to my untrained eye..

Also from the installation guide it seems there are no flow restrictors so nothing should be reducing the pressure I don't think.

Thanks!

 

[seco services]

Have you tried it with the shower head laying in the bath ?

 

[TomWhitson]

Starting it with the head on the floor or below the valve normally gets it started more quickly or in a normal amount of time (if I recall it is still not starting immediately like this 100% of the time)

Also it still will cut out when changing temp when starting it like this.

If this is the case, is it something to consider either,

Removing/replacing the check valves (seems they might need a certain amount of pressure to open?)
Changing from thermostatic to manual mixer (has been mentioned that these normally accept lower pressure better and have wider internal bores?)

Both of these seem to make sense...but no-one seems able to say 100%.

Thanks for the replies.

 

[seco services]

Is there any isolation valves fitted in the pipework ?

 

[TomWhitson]

The shower is gravity fed, so I assume these would be above in he loft space to affect the shower? There are two red valves there but both appear to be fully open. The shower is installed above a bath so there are taps fed from the same pipes, could these have isolation valves inline which need checking? The bath taps are new and were installed at the same time as the shower, I assume they have isolation valves as most new taps do right?

Also I just did a test starting the shower with it turned to hot holding the head below the valve made no difference on this occasion until I turned the shower to cold and it started flowing, once it was flowing I could change from hot to cold and back and even turn the shower off and restart it above head height with no issue. So it seems to me to be related to the initial level of pressur somehow?

Thanks again!

 

[seco services]

The shower is installed above a bath so there are reps fed from the same pipes

What's a rep ?

could these have isolation cables which need checking? The bath taps are new and were installed at the same time as the shower, I assume they have isolation valves as most new taps do right?

only if the plumber fitted iso valves.

Have you got a diagram of the pipework etc to shower ?

And like your 1 m head is being measured from cws to mixer.
It should be cws to showerhead, so really you haven't got 1m.

 

[TomWhitson]

Reps = taps, sorry edited the above post afterward. The shower is above a bath, and I think the taps are fed from the same pipes (at least if I turn the bath taps on the shower pressure drops).

I do not have a diagram I will try to draw something and add it, We have a cw tank in the loft and hw cylinder on the same floor as the shower. From what I can see in the loft space the cw goes directly from the tank across to shower and down, then the bath taps are fed off the same pipes. The hw I assume goes from the cylinder upstairs then down again. Worth noting it is a 1 bed with only 1 bathroom so hopefully piping is not too complex.

As for the head, yes 1m might be optimistic, perhaps 2.x feet to the head hard to measure it precisely. So perhaps it is simply that a pressure issue. But does this explain why it cuts out web moving from hot to cold?

If I recall properly the plumber used flex hoses with isolation for the bath tap as the space was awkward. If the taps are after the shower can these restrictions make a difference to the shower?

Thanks

 

[seco services]

Forget the bath taps they are after the shower.
Personally i think the main issue is your head height is to low, ie raise cws higher in loft to over come that issue.
Any iso valves should be full bore.
And i useally use 22mm pipe to shower then down to 15mm about 1ft from shower.

 

[TomWhitson]

Soiof the main issue is the height, I presume this means looking towards a pumped installation? It should be pretty impossible to raise the head I assume.

Given the pipe work what is the best place to be putting a pump? In the loft, under the bath, in the airing cupboard? There is limited power in the bathroom, one lighted mirror so it seems for that reason the loft or airing cupboard would be better, but does this present any pros or cons in terms of increased flow?

Also someone mentioned getting a combo as you then have mains pressure hot water? I presume this is generally the case, but out shower is 4m above the boiler. So I presume the pressure would be much lower as it has negative head?? Or the boiler has an inbuilt pump?

 

[seco services]

Lifting cws is the cheapest and easiest, providing you got the roof height in loft.

Pump better in airing cupboard.
You'll get better flow/pressure if pumped, Just cost abit more with pump/labour etc.

 

[TomWhitson]

Really lifting the cw is cheaper? I guess it needs raising to have 1m plus of head? Would all the pipe work not need changing (or I suppose just extending up to reach the raised cw tank? )

One person mentioned using a combi boiler to increase pressure, is this 100% correct (clearly this would be more expensive than pump but our boiler is 15yrs old so might die any moment) given our shower is above the boiler I assumed this pressure increase might be quite small?

I presume the reason the previous mixer was ok was just due to luck then really? It seems quite strange that the previous was ok and this one is so tempramental.

 

[seco services]

Really lifting the cw is cheaper? I guess it needs raising to have 1m plus of head? Would all the pipe work not need changing (or I suppose just extending up to reach the raised cw tank? )

It's only a case of making a surport out of timber in the rafters, extending pipework.

One person mentioned using a combi boiler to increase pressure, is this 100% correct (clearly this would be more expensive than pump but our boiler is 15yrs old so might die any moment) given our shower is above the boiler I assumed this pressure increase might be quite small?

Yes a combi would get rid of any loft tanks, hw cylinder and all taps etc would be mains pressure, ie like your kitchen cold tap.

I presume the reason the previous mixer was ok was just due to luck then really? It seems quite strange that the previous was ok and this one is so tempramental.

Was the old one just a manual mixer not thermostatic ?
As thermostatic are more restricted inside than manual mixers.

 

[TomWhitson]

The old shower I think was a plain mixer, it was certainly 12 or so years old and I believe thermostatic is relatively new? Could it make sense to try replacing the thermostatic with a manual mixer then? I suppose it is not guaranteed to fix the issue?

I shall have to check if we have the height to raise the cw, I don't think there is much spare, maybe 2ft. So that would give 4 ft and roughly .15 bar. The current valve states it works from .1 bar so that might help...I suppose I can test by moving the head down 2ft and seeing if it starts better.

For the pump it seems there are many considerations such as size/power, noise, require output pressure, inflow pressure (it seems a certain amount of flow is required to turn them on, will putting it near the cylinder allow for that? So it turns on nice and quickly?). Is there any rule of thumb or some handy guide(s) that you know of?