Electric water heater

Hello all (probably again)

I did post this question in the wrong place. I need to stay in more.

Anyway here goes. I have an electric water heater which suddenly started leaking water from the pressure relief valve. I replaced the valve but the problem persists.

My question is; is there something else I should be looking at before I either call a plumber or replace the boiler?

It has been suggested that the water pressure may have increased, which would also explain some other leaks. All advice gratefully accepted.

Mike. Copper + iron in an acidic solution (water) = a giant low voltage battery =electrolytic action = corrosion & if parts aren't electrically isolated = rapid corrosion , but I assume you already know that. I think your phrase " if it would double the life of the the tank" are the key words here. I don't know & suspect it would take a clever man or a fool to better that statement! Don't know about SS cylinders but I'm sure they would be available.

My first tank only lasted 8 years. When I took it apart I found that the anode was pretty well shot. The replacement has "raccords isolants" so hopefully it will last longer. But I would think it would be worth the effort to replace the anode after 10 years if it would double the life of the the tank.
A stainless steel tank might be a worthwhile investment - do they make those?

Mike , if you can tell me when the anode is gone without taking it out you're a cleverer bloke than me! My logic is to leave the thing until it leaks & then change it assuming of course it's situated in a place where little or no damage can be caused. Cylinders are relatively cheap & easy to change so why beat yourself up dismantling a cylinder just to have a look! I've certainly never tried it & as the things are extracted & replaced from the bottom I doubt that most installations have enough height below to do this. I have seen some bendy jobs which might do it but I certainly couldn't be arsed to attempt it. Far too much risk for the reward of not changing what is probably a corroded cylinder anyway. I guess it all depends on the installation. If you have good dialectric connections to copper pipework or an all plastic system the thing has little risk of electrolytic corrosion so should last many years. There are cylinders in my area still going strong after 20 odd years.

A slight diversion.........

Has anyone ever replaced a sacrificial anode?
Were did you get the replacement?
Is there a standard size, or do you have to take the heater apart to find out what replacement is needed?

ahh...what we used to call an indirect water cylinder in the UK. From what I remember they were fairly cheap in the UK......but then that was a while ago, come to think of it ;o))

Dunno about 'superheated' but at 10 bar the saturated steam temperature of hot water is 184 deg C. At 12 bar it's 191 deg. I'm guessing most cylinders would rupture at these sort of pressures so the water would certainly flash to steam with dramatic effects. Cold water obviously wouldn't flash to steam but that, of course, is not what we're talking about here I assume.

I'd have thought you would have to inform your ins. co. if you didn't have one ! Show me a house that has an atmospheric hot water system. Not saying they don't exist but I've never seen one.

Andy - A ballon is any kind of closed water container, I believe. The thing about the préparateur d'eau chaude is that it's a ballon with a heat exchanger that can use any kind of source for the heat to be exchanged, normally provided, I guess, by a closed hot water circuit. The useful thing for Brian, I hope, is that it can also be fitted with an electric heating element for use when the primary source isn't operational.

Thanks for the extra information/ explanation Andy, I know about the need to be registered in the UK, but France seems more lax with these.

They are generally called a 'ballon' as far as I can tell, have a look at the http://www.dedietrich-thermique.fr/ site they have quite a lot of info.

It is a genuine explosion with water no tricks for dramatic effects, water boils under pressure at a higher temperature by the time the internal pressure splits the tank the water is so superheated 300l of water turns to steam in milliseconds. It's the first thing you are taught when you train to install and maintain unvented hot water systems. I the UK you have to be accredited to install/maintain them. The installations have to registered with the local authorities, you also have to inform your house insurance that one has installed but I doubt many people do.

Works well on steam too. Yonks ago I was involved in an automatic coal fed steam boiler melt down. The boiler feed pump had packed up & some idiot had turned off the valve to the 'banjo' feeder which was the auxiliary safety feed to the system. ( the building was about 100ft high) The automatic feeder continued to do it's job resulting in an impressive explosion followed by the meltdown of the boiler tubes. Hell of a mess but very impressive to this young apprentice :-)

Interesting, but water is non compressible so to "Blow" up a water heater they use air which is compressible for the dramatic effect. If they used water the tank would split and water would leak/spray out but no explosion.

Brian - I came across this préparateur d'eau chaude when I was researching a couple of years ago. It seems to be a heat exchanger that can be fitted with an electric element. I have no idea of price, I'm afraid, but I bet your local Aubade or similar could tell you.


and kill you more than likely!

The problem you would have with a wood burner is controlling the heat input into the unvented cylinder.

The electric versions have three safety levels, a thermostat, a thermal cut-off and the pressure relief safety valve, if you connected a wood burner directly you would only have one level the pressure relief which would be highly dangerous if that stuck. There is a way of doing it with a heat exchanger but its complicated you would need an expert to design and install it. Wrongly connected unvented systems can destroy houses.

Understood. I am always ready to learn.

Andy. I was in their Torquay office. G N Haden & sons ltd trained the industry in my days . They had their own training programme & were instrumental in the formation of the National college of Heating, ventilation & fan engineering. The company was originally formed in Trowbridge I believe.

I know you weren’t criticising anyones qualifications Vic my remarks were tounge in cheek. Where did you work for GN Haydens? I know they had a branch in Manchester and heard them mentioned often as where colleagues started out their careers.