Pumped hot water loop alternative

[JonathanM]

Our bathroom is a long way from the megaflow tank and it takes a while for the water to run hot at the tap. No problem for filling the bath, but would be nice to have warm water available immediately at the sink

Is there a way to fit a valve under the sink piped to the toilet fill so that it would use the hot water pipe until the water came hot, then complete the fill with the cold water pipe? Wouldn’t cover every eventuality, but washing hands after using the toilet is probably the main use of the sink

Brian

It sounds good to me. In my ensuite, I can reach the hot tap with a stretch from the loo and have become pretty expert at turning it on at exactly the right time.

 

[Daveydub]

You could always fit one of these, blended supply to wc and set it to about 20 degrees. Would draw mostly from the hot pipe till temperature achieved and then continue to fill cistern with mostly cold.

Flomasta Thermostatic Mixing Valve 15mm - Screwfix

Order online at Screwfix.com. Thermostatic mixing valves are used to maintain the domestic hot water supplied to the user at a constant and safe temperature, when variations in the hot and cold water supply conditions and draw off flow rates occur. Failsafe design shuts off the water flow...

www.screwfix.com

This will be full of problems like ambient temperature (where the valve is) and temperature of cold water (if cold pipe runs alongside hot or heating pipes) and so on.
Be very interested to see what solution you arrive at.

 

[trojanhawrs]

No, it appears to be glued - was in when my wife bought the place. Looks nice, but can’t get to anything. Certainly don’t want to risk breaking it

If I could, I would try your idea, but I think I’ll have to try a thermal switch and valve unless we get any better ideas

Thanks,
Brian

Think you'll struggle to find a thermostat for that application.

Do you have easy access to the pipework under the sink and access to the fill valve pipework?

 

[brig001]

You could always fit one of these, blended supply to wc and set it to about 20 degrees. Would draw mostly from the hot pipe till temperature achieved and then continue to fill cistern with mostly cold.

Flomasta Thermostatic Mixing Valve 15mm - Screwfix

Order online at Screwfix.com. Thermostatic mixing valves are used to maintain the domestic hot water supplied to the user at a constant and safe temperature, when variations in the hot and cold water supply conditions and draw off flow rates occur. Failsafe design shuts off the water flow...

www.screwfix.com

This will be full of problems like ambient temperature (where the valve is) and temperature of cold water (if cold pipe runs alongside hot or heating pipes) and so on.
Be very interested to see what solution you arrive at.

That's a good idea, thanks Daveydub

Yes, none of these ideas are perfect, and the valve temperature would never match the pipework temperature exactly, but if I can get 90% of the performance of a pumped loop for 10% of the cost, I call that a win - actually if I can 75% for 25%, I'd still be happy

Brian

 

[brig001]

Think you'll struggle to find a thermostat for that application.

Do you have easy access to the pipework under the sink and access to the fill valve pipework?

I was going to try:

Drayton Pipe Thermostat - Screwfix

Order online at Screwfix.com. Pipe thermostat for use as high or low limit on domestic or commercial systems. Frost protection solution when used in conjunction with the RTS3 air frost thermostat. FREE next day delivery available, free collection in 1 minute.

www.screwfix.com

but it might take too long to sense the temperature and switch, then there's the delay in the motorised valve...

Under the sink, yes
I reckon I could get a new pipe to the cistern and join it to the existing pipe by drilling through each cupboard at the top back and using plastic pipe - not straight forward though

Brian

 

[Harry Bloomfield]

Yes, none of these ideas are perfect, and the valve temperature would never match the pipework temperature exactly, but if I can get 90% of the performance of a pumped loop for 10% of the cost, I call that a win - actually if I can 75% for 25%, I'd still be happy

IMHO - The whole idea of somehow piping HW to the flush tank, is a none-starter, because it will be no quicker than simply turning the tap on and waiting - unless you were to walk in, and flush first.

 

[trojanhawrs]

IMHO - The whole idea of somehow piping HW to the flush tank, is a none-starter, because it will be no quicker than simply turning the tap on and waiting - unless you were to walk in, and flush first.

Won't it though? If you have a high flow going into the cistern it'll clear the pipes quicker than you can at the sink without getting smashed in the face with water. The PIR idea's not bad but you'll hear water flowing into the drain when you walk into the toilet which would get on my tits.
You'll need that thermostat, a 3/2 solenoid and adapter fittings from 3/8 to 1/2". I'd plumb the hot into the NO side of the valve so it's always ready to go as soon as the flush is activated, saves on electricity too as the solenoid will release as soon as the pipes cool down again.
You'll also need to work out how you're getting cables to the thermostat* and solenoid, each only have 1 gland for cables to maintain their IP rating and you likely have to run them out of the bathroom to a junction box and fused spur. I also don't know about plumbing regs for mixing hot and cold mains, mixing in the cistern is different as it acts as a break tank.

 

[StephenStephen]

I'm wondering if there's an advantage to keeping the cistern empty, so that it fills when you go into the room...?

 

[Harry Bloomfield]

I'm wondering if there's an advantage to keeping the cistern empty, so that it fills when you go into the room...?

What, the PIR + solenoid valve idea?

The OP would need to check how many litres are stored in the cistern, then try drawing an equivalent amount at the basin, to determine whether it was enough to get the HW to the tap.

 

[trojanhawrs]

I'm wondering if there's an advantage to keeping the cistern empty, so that it fills when you go into the room...?

Not really, you'd be as well just running it to the drain if you don't care about water running as you walk in.
I'd still be trying to get that lid off and squeeze a second fill valve in in situ, stubby screwdriver and a lot of swearing might be the ticket.

 

[Daveydub]

The lower fascia panel will pull off. Usually pull upwards to detach it from the lift off clips.
This will give you much better access.
You may have room for a second ball valve in the cistern but I have no idea how you think that would help.

 

[StephenStephen]

Not really, you'd be as well just running it to the drain if you don't care about water running as you walk in.
I'd still be trying to get that lid off and squeeze a second fill valve in in situ, stubby screwdriver and a lot of swearing might be the ticket.

I'm not following you there - water fresh from the hot tank would be in the pipe (assuming quantities matched) instead of cooled in the pipe, and water would be in the cistern rather than down the drain surely?

 

[trojanhawrs]

I'm not following you there - water fresh from the hot tank would be in the pipe (assuming quantities matched) instead of cooled in the pipe, and water would be in the cistern rather than down the drain surely?

My point is you're going to have audible running water as you walk into the room whether piped to the cistern or to the drain. The beauty of the cistern idea to begin with (for me) is that you're utilising the flush where you'd expect to hear running water.
If you're not bothered about that it'd be simpler just to pipe it into the drain until up to temperature and saves messing with the tank

 

[StephenStephen]

My point is you're going to have audible running water as you walk into the room whether piped to the cistern or to the drain. The beauty of the cistern idea to begin with (for me) is that you're utilising the flush where you'd expect to hear running water.
If you're not bothered about that it'd be simpler just to pipe it into the drain until up to temperature and saves messing with the tank

Ah, different priorities...

 

[Nige F]

Our bathroom is a long way from the megaflow tank and it takes a while for the water to run hot at the tap. No problem for filling the bath, but would be nice to have warm water available immediately at the sink

Is there a way to fit a valve under the sink piped to the toilet fill so that it would use the hot water pipe until the water came hot, then complete the fill with the cold water pipe? Wouldn’t cover every eventuality, but washing hands after using the toilet is probably the main use of the sink

Brian

Nothing wrong with washing hands in cold water - all there was @ my Gran's, after you returned indoors from the outside WC Invest in some carbolic soap.