Shower cuts out when on full power

[morph100]

Ive got a combi boiler and a thermostatic shower in my loft which has been working fine but recently when I turn it on it runs and as i turn it to full power it makes a Clunk noise and then cuts the water off. Only thing that has changed is that since it has been installed we have now started using the heating. I tried running it cold though and the same thing happened. If I run the handheld shower jet attachment that runs fine and they run together fine but when its just the big overhead rain shower bit it cuts out. Also if i turn it up very very slowly I can get to nearly full power before it cuts out, if i turn it quickly it cuts out on only a quarter turn.

Any advice greatly received, so far all I've tried is turning the eco mode off the boiler and making sure no other water is running in the house but its made no difference.

 

[terryplumb]

What make / model is your mixer valve ? If it is only problematic when exclusively using a fixed head ,and works fine with the separate hose / shower head, I would take a careful look at the water outlets on the fixed head ,they make be blocked ( partially) with limescale and restricting the flow ,causing the valve to shut off.

 

[morph100]

This is the mixer http://www.goldtapstore.co.uk/dorato-square-concealed-thermostatic-triple-shower-valve-631-p.asp

It’s only been in a couple of months so doubt it’s had time to build up lime scale yet?

No idea how to take it off the wall and look at the inside as I paid a plumber to fit it....

 

[terryplumb]

If it has been recently installed it certainly won't be limescale. And highly un likely to be anything to do with running central heating.if I understood your post correctly it is ONLY an issue when the fixed shower head is selected. and it works perfectly when the hand held shower head is selected ,and works fine when the fixed head and hand held are selected to work in tandem. If so ,this would lead me to suspect the diverter valve has developed a fault.this should be covered under the guarantee and you should contact the installer to investigate .

 

[Hot&Cold]

It’s only been in a couple of months

You need the installer to visit,its a generic mixer/diverter inlet block behind them blinghy handles.Should be a straight forward as long as the mixer valve suits the supplied water.

temperatures and flow rates need to be checked,your installer will know.

 

[Daveydub]

Are all stop taps fully open?

 

[morph100]

Are all stop taps fully open?

Yep, looks like the shower head is the culprit, if it’s fully screwed onto the arm it blocks the holes the water runs through, if it’s half screwed on the water can flow out. For some reason the outlet holes are in the screw thread! Bizarre

 

[terryplumb]

What a crazy design !! At least you sussed it. Any chance of a pic ,I am intrigued !!

 

[morph100]

What a crazy design !! At least you sussed it. Any chance of a pic ,I am intrigued !!

 

[morph100]

Do I just leave it half screwed on or is there something I’m missing here?

 

[terryplumb]

Is that a rubber O ring seal in the bottom ? If it is then surely it must be tightened down to compress the seal ,so water will not escape around the threads ? It maybe that the problem is elsewhere and by loosening the head you are making enough of a difference in the resistance to allow it to work. I would get the Installer back .

 

[morph100]

Is that a rubber O ring seal in the bottom ? If it is then surely it must be tightened down to compress the seal ,so water will not escape around the threads ? It maybe that the problem is elsewhere and by loosening the head you are making enough of a difference in the resistance to allow it to work. I would get the Installer back .

The only way out for the water is through the threads, the installer said he hadn’t come across anything like it and suggested not fully tightening but surely there’s something missing?

 

[terryplumb]

Photo of the end of the shower arm. In close up ,might help ?

 

[Daveydub]

If the shower arm has a flange at the top of the thread, move the o ring on to the shower arm thread. It will then compress between flange & head to provide seal and allow a bit more room beneath the end of the arm for water to flow. Alternatively throw o ring away and assemble with ptfe tape screwing on 2 or 3 turns.