Shower won’t turn off - after valve replacement

6 Jun 2020
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United Kingdom

I have a concealed shower that had developed a drip from around the handle. I therefore ordered a replacement flow cartridge and fitted it.

However now when I loosen the isolator screws on the hex nut to restore the water supply, water pours from the shower head irrespective of whether the flow cartridge is in the “on” or “off” position.

Grateful for any suggestions on what I’ve done wrong / what the fault is.

PS: I also tried refitting the old cartridge and have the same issue.
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What parts did you have left over after the rebuild of the old cartridge :oops:
You need to supply further information with respect to valve manufacture and model number in order to get a reasonable guess at the problem.
Apart from that did you explicitly follow the manufacturer's installation instructions
Thank you everyone for the replies

I have included a picture of the valve housing and the cartridge. I simply replaced the old cartridge with the new cartridge rather than strip down the old cartridge and replace the ceramic discs.


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1/4 turn ceramic valves, standard stuff, you do need to compare the old to the new valve to ensure the reach and seal is the same though. Is that the new valve or old valve in the pic as that valve seal doesn't seem right. Far too much silicone grease on it too, just a light coating is needed.
That is the new valve, however all of it’s measurements are exactly the same as the old one.

The valve seal looks the same as the old one (albeit red rather than blue). The ceramic discs are different in that the new ones appear to have smaller holes when in the open position.

I've fitted quite a few of this type of valve - but on domestic taps, not a shower.
The red differs from the blue insofar as one turns on clockwise and the other turns on anticlockwise (ie hot versus cold)

You can pull them apart (if you're careful and keep an eye on the way it all goes back) and turn one of the the ceramic disc through 90 degrees and this has the effect of converting it from hot to cold (and vice versa) ... but it's easier to get the right colour in the first place.

Screwfix do a couple that just happen to fit mine but I do know that there are about six million different sizes - and they all look similar.
There should be no grease or whatever on the ceramic faces as that will prevent a water-tight seal. I know that sounds non-intuitive but that's how they work ie face-to-face

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