Trevi boost shower issue ad overflow

[tatters40]

Hi All

I have recently had an issue with my trevi boost shower, basically i have a very limited flow of water which does get hot but only trickles from the shower head. I removed the boost cartridge which seems like a sealed unit and placed it back in position. If i now switch it on i get no hot water out of the upstairs taps (downstairs ok) or the shower head but i'm now getting water out of the loft overflow (Large plastic tank in the loft). it seems somehow that water is being forced upwards into the tank. I initially thought of a coil issue in the immersion tank but this has only started since i removed the Boost Cartridge

Any ideas

 

[Ben-gee]

Isn’t the Trevi Boost a Venturi shower I seem to remember?
I suspect the mains fed cold side is back feeding up the hot supply pipe. The non- return valve in the hot side is not working or missing.

 

[tatters40]

Isn’t the Trevi Boost a Venturi shower I seem to remember?
I suspect the mains fed cold side is back feeding up the hot supply pipe. The non- return valve in the hot side is not working or missing.

Hi thanks for the supply

I have a gate valve in the loft on the 22mm hot supply to the shower is this what you are possibly referring to?/

 

[Riley]

No it’ll be on the shower itself

 

[tatters40]

No it’ll be on the shower itself

Hi Riley, thanks for the response, had a look for it and can't see anything and not shown on there schematic

 

[Ben-gee]

If there really isn’t one, which I’m pretty sure there must be, then try adding a non return valve in the hot supply pipework as near to the shower as you can

 

[tatters40]

Hi Ben-gee, there is mixer on one side which seems to be ok and a venturi boost cartridge on the other. All i have done is remove and re install the boost cartridge. Apologies for the constant questions but just trying to understand the need to put a non return valve in when there never was on, it may be the answer but it worked previously

 

[Ben-gee]

The need for an nrv is precisely the symptoms you stated in your first post.
I’m not too familiar with your particular shower, but most NRVs are small white plastic discs with a spring loaded centre, usually fitted at the point the valve connects to the pipework.
They are inside the brass casting and you won’t see it unless you remove the valve from the pipework

 

[tatters40]

Hi Ben-gee
Thanks for the reply, only just got back after working away, followed the hot water supply back from the gate valve back to the top of the Immersion tank in the airing cupboard, no non return valve inline. On the cold supply there is one on the shower side of the stopcock which is directly above the shower in the loft

 

[Ben-gee]

If you’re not going to read my posts I won’t bother helping any more.