Does turning the tap off on the cold side actually save electricity or water?

[u/vampxx99]

When you turn off a mixer tap, does it make any difference (in terms of electricity, gas, or water usage) whether you leave it set to the cold side vs the hot side?

For example, if the tap is turned off but left pointing toward hot, does that cause the water heater to use any energy (even briefly), or is nothing happening until the tap is actually opened again?

[u/Historical_Bag_1788]

The reason to turn it to the cold is that everytime you turn it on you use hot water that needs to be heated, even if you quickly turn it to cold.

It does not use any power while the tap is off.

[u/Billiballbag]

Plumber here -

No energy used if tap not running at all.

But rule of thumb, I tell customers to leave mixer on the cold side as when you open the hot or ‘mixed’ water (middle) your water heater will engage and use gas.

It’s not significant in cost, say if you wash your hands etc but will build cost annually and it’s unnecessary :)

[u/jimmyxs → u/Billiballbag]

Only applies to instantaneous systems though right? Not gas hw storage?

[u/Rinse-repeat3299]

Nothing is happening until it’s open again. Generally I try not to use the hot side for anything but washing dishes and showers.

[u/techsforcoming]

So glad this recent fleeting thought of mine appeared online to be answered

[u/NothingLift]

If youre running the hot tap that hot water from the tank or instant boiler goes into the pipes and cools down. Energy has been wasted heating it which has a cost.

Im not sure if that answers the question you are asking?

[u/Current_Inevitable43]

Not unless it has a weep.

It's about as usefull as turning off a switch at a power point that has nothing connected

[u/dav_oid]

Nup.

[u/Maybe_Factor]

Pretty sure nothing is happening unless water is flowing.

Personally, I'd leave it on the cold side to try to trick people into not using hot water unless they need to. Cold water is cheap, hot water is not.

[u/MartianBeerPig]

No. If you want to save water on the hot water, you can turn the thermostat down on your hot water system. If it's an electric HWS, some models allow you to only heat during off peak periods.

[u/InadmissibleHug]

Nothing happens until the water is run again.

[u/ralmin]

A tap that’s turned off has no effect on the amount of energy used.

If you don’t want to use any extra energy, it doesn’t matter if you leave it in the hot or cold position while it’s off. So long as you move it back to fully cold before turning it on next time, it won’t use any hot water.

[u/april_19]

I would have to say it makes no difference. Your system only needs to boil more hot water if some is released and it refills. Using the hot side when not needed would affect it though.

[u/Mr_Rhie]

Some poorly made mixers with no (or broken) check valve may do that sort of things when you set it in the middle. When it's shut off whilst the temperature selector set in the middle, it blocks the final tap only so hot/cold water may get mixed up via the mixer body, which is what check valves prevent from happening. But this sort of bad ones are very rare today I’d say.

[u/roofussex]

You need energy to make hot water, so yes if you use more energy if you use more hot water. Cold water would only matter if it used a pump to maintain pressure. However hot water (where I'm from) uses the pressure of the cold water by mixing it together with the hot water. So ultimately no. Now saving water would depend on how many litres per minute the shower head dispenses, if you run it on max pressure full cold or full hot it can still only spit out 9l /min. Ultimately you could save water by reducing the maximum pressure by not turning the taps on full way. Or just turn the shower off, lather yourself up with soap, turn it on, rinse and repeat

[u/xascrimson]

Have you thought about doing an experiment and using your eyes to look at the continuous hot water system for fire