Tuesday, July 6, 2010

Hot Water System

Can anyone tell me if my not-heating-up-enough-in-the-cold off-peak hot water system has a thermostat I can adjust? Suddenly it doesn't seem to be very hot.

I'm having house guests in a few weeks and the last thing I need is to have to get a new hot water system.


Pedro the Ignorant said...

It is pretty a pretty straightforward procedure on most electric storage systems.
First, measure your hot water temp from the tap with a cooking thermometer, and decide how much hotter you need the water.
There are usually two thermostats on most home HWS, located behind screw on covers at the top and bottom of the tank.


Remove the thermostat covers, you should see a dial with markers usually a white triangle pointer and a scale with degrees C marked. Use a screwdriver to adjust BOTH thermostats to the same setting. Reinstall the covers.

Turn power back on, test water temp again straight away, then twice more at 30 minute intervals.

Be aware that raising the water temperature will increase your power usage and costs.
This is general advice for a standard HWS but if you are not confident in doing this, particularly about ensuring the power is turned off, call a professional. It is a simple job on most systems and will not cost the earth to fix.
Good luck.

Stevo said...

One of the elements may have broke. I had a Rheem electric water heater connected to off peak, it just warmed the water when one of the two elements blew. I got a plumber in to replace it. If the heater is 10 years old, you need to start saving for a replacement.

Patrick Carroll said...

if you leave it alone and have cold showers the greenies will thank you for it!

kae said...

The water isn't lasting like it used to, it's going cold very fast...
Thanks Pedro, I might get someone who knows what they're doing to fix it. A new HWS is probably out of my price range at the moment - you have to buy one of those stupid green things that cost more and are less efficient.

Mine's a Rheem, connected to off-peak. And it's only 16 and a half years old...

Bugger the greenies I want my hot water!

Wand said...

Kae - off peak water heaters usually only have one element - but certainly Rheem have made twin element hot water heaters. A twin element unit is usually connected off-peak (bottom element) with the top element connected to the normal power. I don’t think you would have one of those.

The unit should have a rating plate with all details - tank size, element size etc on the top - but if it’s 16 years old, the label may have faded or come off. I assume the tank sits outside. I’d suggest that the fact that the water is not heating up will not be due to the thermostat because with off peak electricity, the off peak power is connected to the heater for a sufficient time to allow the water to be heated from cold to hot for any of the types of tanks connected to the system. Rheem make two types of electric water heaters for domestic use - Optima which has an externally adjustable thermostat (I have one of those) and the Rheemglass which has a thermostat that is accessed under the controls cover.

You have done well with a water heater lasting 16 years. My guess is that the likely reason for the water not heating will be a build up of silt in the bottom of the tank to the point where it is encroaching on the element. It is possible to remove the element from the tank to flush the tank - but it has to be done with care. The water rushes out and particular care is required to ensure the power is isolated. Actually I did do this once many years ago when I replaced the element on the off peak water heater at the time. The amount of silt in the tank was something else! Mind you, the heater didn’t last too long after that. The tank failed which is the most common failure that occurs. The glass vitreous enamel develops a pin hole and starts leaking inside the external insulation and cladding and then it’s done its dash..

Anyway, enough of this. I’ll scan relevant pages from the Rheem hot water manual and send them directly to you so you can see what it is all about.

kae said...

Hi Wand, et al.

I have had some experience with dead hot water systems. One electric in Qld, the water just didn't heat and I think eventually the water started gushing out of the tank, the boyf turned it off and when I got back from Sydney there was no hot water... he'd done nothing about it. I guess he was showering for the time at his extra horizontal-folk-dancing partner Corporal's unit, so didn't need the hot water. He'd not even phoned the agent to get it replaced.
In Melb. a gas hot water system had died, the pipes passing thru the tank had developed the pin hole and the water flowed into the tank and overflowed it into the gas burner... at least the ex husband sorted it out pretty quickly! It was Melb and it was winter!
I've just phoned about my one and a new 315L Rheem will cost me $1135 cash, or about $50-60 more if I get it interest free on their system. Then I need to get my usual electrician to install it. He's good, it's just getting him that's the problem. About $100-150 to install at a guess.
I guess I'll have to bite the bullet.
I did run the water to fill the jacket (I think it's called) last night but it overflowed so that's not why the water's not heating up. I didn't think to check that the tank had been leaking... Bugger! That would have been a hint that there's a pinhole leak in the internal pipes....
Thanks everyone.

kae said...

The torch I have is crap, too. So it would have been hard for me to see whether the overflow had been leaking.
There was a cane toad living there, too.

kae said...

The torch I have is crap, too. So it would have been hard for me to see whether the overflow had been leaking.
There was a cane toad living there, too.

Wand said...


The "overflow" you talk about is actually a safety temperature and pressure relief valve designed to open on excess pressure or temperature (it is after all a mains pressurised tank) and if the element did not shut off the tank would overheat.

Sometimes they can 'leak' - i.e., slowly trickle and the trick here is to 'crack' them by operating the external lever to flush the valve (of dirt under the valve seat). Most often this is all that is required and the valve will then reclose.

As I said earlier, my guess is that most of your problem would be due to a build up of silt in the system.

You said you ran the water to fill the jacket but it overflowed???? Don't understand. If the tank has been leaking usually it will be evident with a lot of water around the base and sometimes it can be difficult to detect.

kae said...

Hi Wand
I've also had the situation when the hot water system wasn't heating or staying hot long enough when it had worked OK before. This was a problem with evaporation from the surrounding hot tank and you needed to re-fill the tank by opening the overflow to make sure that the tank was full.

wayne Job Broadford Victoria said...

It seems many people visit your site and rarely comment, when some thing goes wrong the men come out of the wood work to offer advice.
Being an old engineer, it is certain that all modern appliances are designed to a price and ten years or more is a good innings for a hot water service.
Just bite the bullet and replace it, it ain't worth trying to fix it. { hint suck up to the bloke installing it, for it will be politically correct kiddie safe and only ever warm, not even hot enough to do the dishes. Ask him to make it hot, use your natural talents, for it is illegal]
Good Luck