Immersion Heater Problem

[kinslerp]

I need to fix a failed immersion heater in my hot water cylinder; which seems in principle straightforward enough. The problem is there seems to be no way of draining water out of the cylinder without removing one of the elements! There are two heaters, both side mounted one about a third of the way down, the other at the bottom.

There is a "bolt" just below the top element, which might be where a drain tap of similar should have been fitted, but I don't actually know what it's for (if anything).

The hot water is drawn from the top of the cylinder, cold goes in at the bottom; so shutting the inflow and opening the hot taps has minimal effect on the amount of water in the cylinder.

It looks like I'll just have to take out the top element and try to catch as much as possible in a bucket. Unfortunately, it's at least several buckets worth, and it's going to gush out when I remove the element -- and I'm not sure the flat downstairs needs an in-house waterfall.

So this all sounds pretty impossible to do with any degree of dryness. Any one got any suggestions or miracles that might work better than a lot of towels and a hopeful waving of buckets?

Thanks, #Paul

[MrCheerful]

Get a pro with a pipe freezing kit to put a drain c*ck in the water inlet.

Turn off the water further away and let the water syphon out of the tank via the inlet.

Disconnect the inlet and let it drain from there.

Remove the outlet pipe after draining as much as possible and use a hose to syphon out the tank.

MrCheerful

[Niall]

Shut off the cold supply and open a tank fed cold tap below the level of the cylinder if you have one. Otherwise disconnect one of the top connections after draining as far as possible, then insert a length of hose and syphon.

[Ed Sirett]

Look around at the pipework on the inlet into the bottom of the HW cylinder (HWC). There may be a) a drain point (attach hose expect the drain point to dribble a lot). b) a valve at low level: possible to close it off, drain _roof_ tank (using cold water) and then open the non HWC side pipework and use the valve to control the emptying of the cylinder messy but possible. c) with the inlet off you can drian to the top of the cylinder level. you then open the pipework at the top of the cylinder (might not be easy) and put a hose from the top into the cylinder to syphon off the HW. When completely empty you can work on both immersions. Also add a tee and a drain point or 1/4 turn service valve for future use.

HTH

[Set Square]

My hot cylinder has a drain tap at the bottom of the cold feed pipe - just before it goes into the bottom of the cylinder. What size is your cold feed pipe, and can you get at it? I'm wondering whether you could fit a tap in it, using the sort of clamp-on and pierce fitting ** somtimes used for outside taps and washing machine supplies. That would, at least, allow you to drain it in a controlled fashion. If you don't fancy that as a long term solution (not sure I would!) once the cylinder is drained, you can remove the temporary tap, cut out the pierced section of feed pipe and fit a proper drain tap for future use.

** Not sure I've ever seen these in anything other than 15mm - so if your feed pipe is 22mm (which it likely is) this may not be possible. Anyone seen any of these things for 22mm pipes?

[kinslerp]

Now I look at the tank again, there's actually a a small tap just below the bottom element -- I hadn't noticed it before because it's so close to the floor. So I just need to get myself a bit of hose to wedge onto it.

And many thanks to everyone for all the replies.

#Paul

[Set Square]

One final tip. Loosen (but don't remove!) the old immersion heater *before* you drain the cylinder. It will be *much* easier with the weight of water keeping the cylinder still. It will probably require a *lot* of shifting - maybe by sliding a metal tube over the handle of your immersion spanner to get greater leverage.

[Christian McArdle]

Yes, and be aware that failure is quite common. You should have a contingency plan to replace the cylinder. If you could benefit from a different system, such as a heat bank etc. then consider this now, so you don't just replace like with like in a panic when an upgrade could be beneficial.

Also, ensure that the water supply is shut off and the hose connected when starting to loosen the immersion. If the cylinder splits, you can then, at least, start draining down the cylinder rather than waiting for the entire contents to spill out.

Christian.

[Niall]

Yep. Last one I had a hand in taking out, when it finally shifted the thread insert in the cylinder cracked, and the replacement wouldn't seal.