Problem with shower - old style electric hot water

[Kimberlee]

Hoping someone can please help. I have an intermittent fault with my electric hot water. I have an older style electric hot water service that heats on controlled load over night. The large tank is in roof space of 60s built villa unit. Every few mornings, no hot water will come out of shower. When this happens pressure is reduced at all other taps. A gurgling sound comes from the shower. I can get around it by turning on the cold full while hot tap is on. When I turn off cold, hot has come through. Plumber has replaced hot shower tap washer. Also reseated hot tap but problem persists. I have cleaned out the shower head. Other change is a doubling of my electricity usage in the last quarter. I think that the water temperature is hotter (now scolding) than before and bill suggests a change (hot water is my main electricity cost). Very happy to provide more information or answer questions as needed. Many thanks!

 

[Ben-gee]

It sounds like you have an airlock in the hot water pipework - you cleared it by also opening the cold which seems to have pushed the air bubble out and up the vent pipe , restoring the hot water.
However it reoccurs.
I suspect the thermostat on the heating element is faulty and allowing the hot water to overheat, maybe even boil, this could be causing the airlock.
Test the thermostat and replace if necessary.
Clear the airlock, preferably by suction on a hot tap, or by mains water pressure from a cold tap to a hot tap. Either method do it for a good few minutes otherwise you will just partiallly clear it and not solve the problem. But be careful not to overfill the cold water storage tank, hence preference for suction method where this is not possible.

 

[Kimberlee]

It sounds like you have an airlock in the hot water pipework - you cleared it by also opening the cold which seems to have pushed the air bubble out and up the vent pipe , restoring the hot water.
However it reoccurs.
I suspect the thermostat on the heating element is faulty and allowing the hot water to overheat, maybe even boil, this could be causing the airlock.
Test the thermostat and replace if necessary.
Clear the airlock, preferably by suction on a hot tap, or by mains water pressure from a cold tap to a hot tap. Either method do it for a good few minutes otherwise you will just partiallly clear it and not solve the problem. But be careful not to overfill the cold water storage tank, hence preference for suction method where this is not possible.

Thank you Ben. I appreciate your diagnosis. Is clearing the airlock using suction on a hot tap something I could safely do myself? If so could you please explain the process. I would need to find a way to do it without burning myself as the water is coming out very hot. Thank you.

 

[Basher]

I urge you to get the thermostat in the hot water tank checked/changed, as it looks as if it's faulty and no longer controlling the hot water to a safe temperature.

Not to be over alarmist, but if the water overheats to boiling point, you have a potentially dangerous situation. If there's no pressure relief, or if that doesn't work, you could get a burst and boiling water pouring through the ceiling! There have been some horrible accidents in the UK through faulty thermostats in electric heaters, although these are further compounded here by the use of plastic tanks in the loft, which I doubt is the case with your installation.

Scalding risk from domestic hot water systems - Safety alert

Safety alert issued following a second fatal injury caused by the failure of a domestic hot water system.

www.hse.gov.uk

The airlock problem should go away once the water temperature problem is resolved.

 

[Lou]

How did you get on?

 

[Kimberlee]

How did you get on?

Hi Lou, I had two excellent responses from BenGee and Basher. It sounds like an airlock and thermostat are the problem. I have been away this week, and haven't had a chance to get an electrician in. I turned off the hot water as a precaution after the cautionary advice while away. I have to decide which way to go now. Do I pay for an electrician to fix the thermostat in an already 60 year old system, Or do I put the money towards a new hot water service. I don't know which way to go. First step I think is call an electrician and get a quote to adjust thermostat. The airlock is still occurring as I wasn't sure if I could clear this myself and if so how.
Thanks for checking in Lou.

 

[Basher]

Do I pay for an electrician to fix the thermostat in an already 60 year old system, Or do I put the money towards a new hot water service. I don't know which way to go. First step I think is call an electrician and get a quote to adjust thermostat.

I have to admit that I don't know what a 60 year old Australian water heating system comprises, but if it's anything vaguely like a UK one, I wanted to reassure you that it should not be complicated or expensive to fix.

It's not that the thermostat needs adjusting, it's that it's probably faulty, so it's for an electrician to replace.
In the UK the part is about £10 to £15, and a replacement should have a built-in safety cutout inside these days, designed to avoid dangerously hot water, which yours seems not to have.

If it helps, the heater element in your hot water tank, the bit on the left below, should be OK as it's obviously still heating!
The bit on the right slips into a pocket on the heater, so the electrician would just undo the wires, pull it out, push a new one in, and put the wires back. There are other configurations, e.g. where the thermostat is a separate box on the side of the cylinder, with a probe going into a tube on the cylinder, but it's essentially the same function and usually easy to replace.

Of course it might not be as simple as the above, if your hardware is different, or if I am mis-diagnosing the fault, or if the electrician has to travel 100 miles to get a spare part!! But it is an essentially straightforward task in principle.
I hope this might help "de-mystify" the job - I apologise if I'm going on about what you already know!
Best of luck!