Cold feed to shower

[blawford]

Yesterday morning my upstairs shower would only give me uncomfortably hot water, I tried adjusting the temperature control and it wouldn't change the temperature but adjusting it to its coldest setting would make the water stop altogether.

The shower is [DLMURL="http://www.wickes.co.uk/Wickes-Cascada-Thermostatic-Mixer-Shower-Chrome/p/212534"]this one[/DLMURL].

Got home from work yesterday and tried the shower again, even worse than the morning, only a trickle of water came out and then it stopped altogether (no matter what I did in terms of temperature adjustment) so I turned the water off at the stopcock to allow me to investigate further.

After taking it apart I couldn't see anything wrong so assumed the cartridge was probably to blame, although it looked fine. I wasn't able to get a replacement part from anywhere local, so I reassembled things for the moment so that I could turn the water back on to the rest of the house. When I did so the shower worked for a short while (a minute or two, seeming to coincide with the cistern of the toilet filling in the same room) before stopping again.

With the shower now not doing anything (and the cartridge looking in good shape) things seemed not to add up, so I decided to take it out again, leave it out and turn on the water at the stopcock. After doing this it is clear that I only have hot water feeding the shower, the pipe on the cold water side of the valve has nothing coming out of it.

My thoughts/guesses so far:

• The hot water feed alone doesn't have enough pressure to produce water at the shower head? Which is why initially when adjusting the temperature control to cold would stop the shower (turning off what little cold water there was at the time would reduce the overall pressure too much).
  
• Given I can get the shower to run very briefly, sometimes, and it seeming to coincide with water running to other places (toilet cistern etc), could it be some kind of air in pipes type issue?

Few points of note:

• The cold tap to the sink in the same room seems fine, good pressure, although sputtering
  
• I have recently been renovating the downstairs bathroom, although I haven't turned the water off or made any plumbing changes there for about a week (and even then it just turning the water off to fit the taps on a basin). I can't see how this is related but figured it was best to mention.

I have a combi-boiler and I assume there is no pump powering the shower, although I'm not positive on this.

Any thoughts on what is going on?

 

[steadyon]

Its not clear from the above whether you have taken the cartridge out of the shower, or the shower off the wall.

1. Get the instructions from http://travisperkins.scene7.com/is/content/travisperkins/T3274_212534_TECH_1
2. Turn off water.
3. Remove entire valve from wall leaving only pipes coming out of wall.
4. Get someone to turn on water briefly while you watch pipes coming out of wall.
5. Turn off water.
6. If water flowing from both pipes, clean filters per instructions. Refit valve, try again.
7. If water NOT flowing from both pipes (at 4. above) obstruction / air-lock elsewhere in DHW system

Good luck

 

[blawford]

I have taken the cartridge out of the shower... I have turned on the water with no cartridge in the shower and an empty shower valve body so I can see where the water should be entering the body from each pipe, it is only coming out of the hot side.

So it seems like an airlock in the cold pipe feeding the shower. I don't know the plumping layout of the room but I assume there is only one cold pipe coming into the room (which is backed up by dramatic loss of pressure in the shower if you turn on the sink taps or flush the toilet while the shower is running). So given the sink and toilet are working the airlock must be in a fairly small bit of pipework?

 

[steadyon]

Airlock on a combi system is pretty rare.

The filters are often combined with a non-return valve, which is normally just a nylon valve, spring loaded to allow flow in one direction only. These can stick in the closed position with lime-scale / dirt.

You need to clean the filters, which means disconnecting the inlet pipes and taking the body of the shower off the wall per the manufacturer's instructions.

 

[Last Plumber]

Is this shower fed off mains cold water ?
(If you have a combi I would presume so but it is not always the case so I thought I'd ask ) !
If it is on mains I think it would be unlikely to be an air lock if you want my opinion. Unless the shower is very high above ground level and your water mains is poor pressure.

Are you sure you haven't closed any valves or altered any pipework when you changed the plumbing ?

It could be a blockage in the cold to the shower !
Was it previously tank fed or has that shower always been piped from mains ?

Just thought I'd fire some questions out to see if it helps

 

[blawford]

It has always been fed off the mains.

Can't see that I could have made any changes in the new bathroom to affect the old one, due to everything working for at least a week since I made the last change (and as stated, that was only a minor one, the major plumbing changes were months ago now.

Is there a way I can check for a non-return valve? There isn't one visible.

 

[Last Plumber]

Have you took the shower valve off the wall ?
There are normally filters and none return valve built into the elbows on the valve .
I know steadyon has mentioned this.
It sounds favourite to me.
First place to check.
The reason it may work after a while and for a short time could be due to blocked filters allowing a small amount through.

 

[blawford]

Sorry, didn't notice he said they were built into the body of the shower, I googled 'non return valve' and it looked like something much bigger.

Thanks for the help both, I will take a look tonight and report back.

 

[blawford]

The filters are often combined with a non-return valve, which is normally just a nylon valve, spring loaded to allow flow in one direction only. These can stick in the closed position with lime-scale / dirt.

This was it, nothing particularly noticeable came out when I cleaned it but the valve was definitely stuck, I couldn't blow through it in the in the direction I should have been able to. All good now though, thanks for the help.