Guidance on Replacing Bristan Shower Cartridge

[frostyf]

Hi, I own a java recessed Bristan shower and due to a leak from the front of the shower we contacted Bristan who advised that the cartridge probably needed changing.

Following a lot of reading (there are a few threads on this forum) we were sent a replacement cartridge free of charge and I managed (having removed the shower body from the wall) to remove the old cartridge and fit the replacement.

Problem is the new cartridge will only run cold. I've checked the flow (isolated the cold supply left the hot partially open at an isolation valve) and red hot water will come through to the recessed shower body. I've therefore assumed (dangerous) that the non-return valve into the shower body are operating. I've taken out the filters and they're clean. I fit the new cartridge and there's no flow from the hot even with the cold isolated.

Having re-read the installation instructions sent with the shower it simply states to make sure the cartridge is in the closed position, to grease the rubber seals with some silicon grease then fit.

Does anyone know if you need to insert the cartridge at a particular orientation. it appears circular but perhaps it's got to be aligned in a certain way??

I'd welcome any advice

Many thanks

 

[ChrisR]

Seems odd!
Is the cold from a tank / pump/ balanced supply, or the mains?

If you put the hot on and isolate the cold , do you you get hot out?

If so, what happens if you open the cold iso valve slowly?

 

[frostyf]

Hi, the hot is from a pressurised unvented tank. Cold is from the mains (may be balanced although I'm not a trained plumber).

If the cartridge is in the main shower housing I only get cold out. If the cold is isolated and the hot is on, and the cartridge is in the main housing I get nothing out (yes I've turned the valve on once the cartridge is secured in the housing). If I partially turn on the cold and put the cartridge in I get cold out.

If I isolate cold and hot and remove the cartridge, then open the hot at an isolation valve, I get red hot water out. Cold flows out as well. Can't understand why it won't come out through the cartridge when its fitted. Can overpressure on the cold side shut the non return valve on the hot input and stop hot coming in??