Descaling a hot water cyclinder

George_Bray

I live in a hard water area and from everything I've heard, my 20+ year old cylinder is likely to be clogged up with inches of calcium.

Can I just drop in some descale solution to dissolve the calcium, much like you would a small kettle, but on a larger scale?

I have in mind unscrewing the immersion heater element to provide an access hole. Or, if this is a job frequently carried out by plumbers, does anyone know how they do it?

I want to descale the system before fitting a water softener. Otherwise, I figure I may be wasting my time with the softener, if calcium is just 'added back' to the softened water. There should be a heat efficiency advantage, too, if the system is descaled.

Regards
George

Quincy_3

Turn off the gate valve first and cold water supply.

The problem with this is, that the header tank of an immersion heater is usually full of cold water and most descalers work on the principle of hot water, You could always take the heater out and then put it in the garden remove the element and flush out the scale with a hosepipe and refit, as long as you refit properly so ne leaks, ie, Use PTFE tape on the threads and put the tape on the opposite way to the thread so the tape doesnt unravel when screwing in element and fitting cold water supply.

Heath_Robinson

I'm originally from Cleethorpes and the water there is as hard as it comes (I didn't even know what a lather was for a long time...). Our immersion tank used to get very scaled up. I'm talking at least a 100lb of limescale when we came to do something about it. I don't think there's anyway of disolving it on that scale and it was far easier in our case just to fit a new tank and element. Suddenly I could have a hot shower for longer than 2 minutes

Mikeyorks

George. As previous post - replace the cylinder.

Mine had over 50% limescale 'rock' in it ... and only a sledgehammer would have shifted it. Descaler would hardly have touched the surface.The plumber was so bemused at the 'empty' weight he (and his mate) split it open and couldn't believe an immersion still fitted in it.

Get rid - after 20+ years it's likely to be starting to go on the base where you can't see it, in any event. And get your new water softener off to a clean start !

George_Bray

Quincy, Heath, Mike

Many thanks for your suggestions. Your reports on the likely volume of calcium mean one would need wheel barrow loads of descaling chemicals to dissolve it, which is clearly a non-starter.

I'm minded to cut it in half, descale it physically, re-configure the indirect heating coil and braze it all back together again, to be a quarter or a third its present size, i.e. enough water for a single occupant, rather than a family of four. Then run both (a) the normal size new cyclinder and (b) my scaled down old cylinder in parallel, with taps and valves so I can select which cylinder to use, when guests arrive. What's more, to pack a lot of insulation round the smaller cylinder, to make it (hopefully) incredibly energy efficient.

But before I do all that, can you buy very small cylinders off the shelf?

I also noticed that the price of hot water cylinders (at Screwfix) appears to have doubled over the past couple of years. The price of copper perhaps?

Regards
George

Mikeyorks

George_Bray wrote:

with taps and valves so I can select which cylinder to use,

But before I do all that, can you buy very small cylinders off the shelf?

Yes you can buy small cylinders. I had one at the last house which acted as a pre-heater into the hot water cistern, and powered by solar panels.

But - it was a real pain as (reference the first bit of the quote above) the 'taps and valves' which allowed you to use water direct from the 'pre-heat' in the Summer - led to frequent air locks,

It was an inherited system - and I was eventually pleased to plumb it out of existence! Take care you don't create a similar situation?