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Electric hot water tank not generating substantial amounts of hot water.

I have an electric hot water tank in my flat that is maybe ~20 years old. Currently it is not really capable of delivering enough hot water for a bath or more than three showers. Some days even the first shower is only lukewarm. Also if I run the washing machine there is no hot water afterwards. Water pressure is good and we do not have a power/electric shower. We have no gas connection.

The tank has an electric timer programmer that determines when it comes on and has a "boost" option, but the boost option doesn't seem to heat the tank, which only heats overnight. I think the tank might previously have been wired to an off-peak economy 7 circuit but we no longer have an economy 7 tariff due the fact we replaced storage heaters with electric panel heaters.

My questions are basically as follows:

1. Is it correct that the washing machine should draw from the hot water tank? It takes it even for relatively cool washes (30 degrees)?

2. Is there a chance that the hot water tank is just not connected to the timer properly? The tank is capable of heating water to a good temperature.

3. If the hot water tank is on the way out, would you recommend replacing it with a new hot water tank or some kind of electric boiler?

Thanks a lot in advance,

2 Answers from MyBuilder Plumbers

Best Answer

Most older washing machines use hot and cold feeds, the newer ones use cold feed only.
It sounds as if the immersion thermostat has broken, or maybe just been knocked to a lower setting, it may be worth checking this. Switch the power off, and remove the immersion heater cover, usually a nut on top. The thermostat is sat inside the immersion, it should be at a max of 60 degrees, adjust with a small slotted screwdriver, but do not go above 60 degrees.
If this is set correctly, you may have a scale problem inside the hot water cylinder, you need a plumber to come out to check.
If it has scaled up, it won't heat to it's maximum efficiency.
I would recommend one of the new types of electric boiler, get an approved electrician to quote you.


Answered 17th Dec 2013

You mention that you've changed the economy 7 system to remove the storage heaters. Did you have the entire system removed, thereby removing the overnight supply to the lower immersion element in your cylinder? If this is the case, you'll need to re-feed the lower element, either through a timer or a manual immersion switch.
If the boost element isn't working, then you should still have hot water off the E7 system (assuming it's still connected). It sounds like the lower element isn't working for whatever reason and that's the reason why you're volume of hot water had reduced. Your upper immersion element (the boost element) only heats the top portion of the cylinder.

A good electrician or plumber will be able to diagnose the issue but it's one of those cases where you'd have to see it to make a proper diagnosis.


Answered 1st Feb 2015

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