TMV serving toilet cistern

[MortarThePoint]

Is this a crazy idea? I could have a single pipe going to the cloakroom served by a TMV back near the cylinder. It would mean that the water is already warm when it comes to hand washing. And requires only one pipe to be run.

 

Energy would only be wasted in non-heating months and by the lower efficiency associated with hot water from ASHP. Perhaps 3L*50C*1Wh/200%=0.08kWh (=1.5p) per flush in summer and miniscule in winter. 2*4*1.5p=12p/day for family of 4.

 

An alternative is to have a TMV in the cloakroom set to about 30C and pure 'hot' would run until genuinely hot water arrived. This would get rid of the cold water in the hot pipe when the toilet starts filling which is probably long enough before hand washing starts. Energy cost even lower.

 

Would any regs rule this out?

[Carrerahill]

How much pipe are we talking about saving here? Honestly, it seems a bit "crazy".

 

It doesn't allow for consecutive use where hot water might end up going into the toilet, these fill valves are a bit pathetic as it is, even warm water might let the plastic valves flex a bit when warm to a point of leaks/damage.

 

Do you just fit cold water... if just a little infrequently used toilet then cold would probably be fine. 

 

Edited September 29, 2022 by Carrerahill

[MortarThePoint]

1 minute ago, Carrerahill said:

How much pipe are we talking about saving here? Honestly, it seems a bit "crazy".

 

About £60 of parts and labour, so not much. That would be paid back in about in about 3 years. It feels quite 'sensible' from a fast hot water angle though. Cheaper and probably less heat inefficient that a circulating hot water supply to the tap.

[MortarThePoint]

The second scenario also assumes you can set at TMV as low as 30C.