Teenager showers draining the hot water tank

[Doctor Drivel]

Young girlies do not care about the planet at all.

[Doctor Drivel]

It does. It is cheap and will never run out of DIY.

[Doctor Drivel]

Please eff off as you a total idiotic plantpot.

[Doctor Drivel]

The timer ideas are just plain daft. The best way is the plate heat exchanger and bronze pump.

[Doctor Drivel]

They will be in there mooning at night.

[John Rumm]

Not usually. Its a water tank that is usually fed directly from the cold main (and hence needs to be constructed to withstand mains pressure), and has some mechanism built in to allow for the expansion of the water as it is heated (plus various other safety devices). They can be heated electrically (and will often include an immersion element as a backup) but will usually be heated via the central heating boiler - typically via a heat exchanger coil built into the tank.

Andy's post about using a higher placed stat would do much the same. The indirect heating coil from the boiler will usually be placed lower in the cylinder, but the convection and stratification of the water will ensure the hot ends up at the top adjacent to the draw off point.

The most common arrangement like this is a cylinder with one or two heating elements similar to those which you describe. Each has an adjacent thermostat - usually built into a tube running alongside the element. The water feed is to the base of the tank, but it typically from a header tank in the attic (hence is lower pressure than the mains supply) The hot water take off point also usually has a vent pipe that returns to just above the cold water tank in the roof space. This serves to provide expansion room, and also as an additional safety mechanism should the stats fail and the water boils.

Again the same arrangement is more often used with a heat exchanger coil taking heat from a boiler. (using gas heating via the boiler is usually significantly cheaper than using ordinary electric heating here)

Modern cylinders here are usually fairly heavily lagged and don't loose heat that fast anyway.

[John Rumm]

LOL! Now that I can believe.

[Dave Plowman (News)]

Just back from the pub, obviously.

[Dave Plowman (News)]

Another example of how you have no idea about costing. A motorized valve and some simple electronics could do the job for under 30 quid. Don't the catalogues you consume with such ferocity have prices in them?

[Colin Wilson]

...when they have to pay the bill themselves...

[Doctor Drivel]

Please eff off as you a total idiotic plantpot.

[Doctor Drivel]

Please eff off as you a total idiotic plantpot.

[Dave Plowman (News)]

And still not sober even after a lie in. Seek help.

[Doctor Drivel]

Please eff off as you a total idiotic plantpot.

[YAPH]

Thought I'd posted this last night but hasn't turned up here on VM's servers. IF you can get a probe in through the jacket and into contact with the cylinder at a physical position where it'll go cold when the cyclinder's partway exhausted, then fit a 3-port diverter valve with remote thermal sensor head (like a TRV with a remote sensor, that acts like a change-over rather than normally-open switch) into the hot feed to the shower, so it shuts off the hot when the sensor gets cold.

[Doctor Drivel]

And a valve like that made by Danfos will cost more than a bronze pump and plate heat exchanger which will enhance the system no end and increase economy.

[Appin]

The message from John Rumm contains these words:

We run a caravan site which over the course of the season may have at times well over a hundred people on it, and at other times just one or two.

Water heating for showers etc. is by two immersion heaters in a simple direct cylinder -- one at the top, mounted in the standard boss, the other inserted horizontally, fitted in a mechanical flange. Very simple. Low occuptation -- top heater only. 3kW. Medium occupation -- bottom heater only -- 3kW. High occupation -- both heaters -- 6kW. Keeps four showers and hot water for wash hand basins and lundry going without any problem.