TMV valve under bath with 22mm hot water and 15mm cold water mains

[Andy BYF]

The bath taps have 22mm inlets currently the cold water mains 15mm is fixed to the tap by a copper adapter 15mm to 22mm. The hot water is 22mm gravity fed.

Is it ok to add a 15mm T to the cold water pipe and then add 22ml adaptor to the T to connect to a 22m TMV .
I cannot find any TMValves with different intake sizes. The pressure on the hot pipe is very low as the tank is also on the bathroom floor.

 

[Dave Moore]

Hi Andy,
This should be ok as it’s simply throttling the water to ensure it comes out at a preset temperature to prevent scalding.
regards,
Dave

 

[Ric2013]

My understanding is that TMVs are not designed to be used on unbalanced pressures, generally speaking. If you want to connect a TMV in a mains cold/gravity hot situation you would do well to confirm product suitability with the manufacturer of the TMV before starting works.

 

[Timmy D]

My understanding is that TMVs are not designed to be used on unbalanced pressures, generally speaking. If you want to connect a TMV in a mains cold/gravity hot situation you would do well to confirm product suitability with the manufacturer of the TMV before starting works.

If we understand correctly that the hot is gravity and the cold is mains, the mixing valve won’t work.

Why do you want to add a mixing valve.

 

[fowlerboi]

Interestingly my take was that the blending valve was done by gravity and the cold mains was just doing the cold side of the bath taps. (which will work)

Need a photo really

 

[Timmy D]

Interestingly my take was that the blending valve was done by gravity and the cold mains was just doing the cold side of the bath taps. (which will work)

Need a photo really

I assumed they wanted to feed the blending valve with gravity hot/mains cold.

 

[fowlerboi]

I assumed they wanted to feed the blending valve with gravity hot/mains cold.

My thinking is that a TMV for a bath is typically a new build (rarely ever seen any on refurbs) and I would expect a plumber on a new build to know better than to gravity/mains mix a TMV

If its a refurb then yeah could easily be mixed by some cowboy

 

[Timmy D]

My thinking is that a TMV for a bath is typically a new build (rarely ever seen any on refurbs) and I would expect a plumber on a new build to know better than to gravity/mains mix a TMV

If its a refurb then yeah could easily be mixed by some cowboy

I agree.

The op seems like a non professional wanting to add a TMV to their own property.

Ah well, only op has the answers.

 

[fowlerboi]

You're right. Completely misread the OP