Connecting replacement hot water cylinder

You can use either, although there is a particular sealant that is supposed to be used for potable water connections which is green in colour.

There should be a fibre washer with it. Nothing else is needed. Tighten on fitting but not too much. Fill the cylinder and tighten more to stop seepage. A little is OK because it will usually stop when the washer swells.

If you have any of those red wheeled gate valves, now is the perfect time to cast them into outer darkness and replace them with lever ball valves. These are quarter turn valves with a handle and are full bore so don't restrict flow. They don't stick and don't leak around the spindle.

Try to avoid having any connections to the cylinder in inaccessible positions. The one that will leak will be the bottom one at the back.

If you didn't buy a new immersion heater, you should. Firstly you can get better quality ones than are typically fitted by plumbers for only a few pounds more and also the latest ones have an additional safety cutout.

Top tip is clean out all old sealants from compression fittings on pipework,if you have a olive cutter remove old olives an replace with new.do not overtighten the immersion until there is water in the tank it is very easy to damage at this stage.

"Andy Hall" wrote

To clarify: It is important to specify full bore ball valves at time of purchase for fitting around the hw cylinder. By default, you will be offered reduced bore (much cheaper but will restrict flow).

Phil

The message from "Alex" contains these words:

And consider copper-grease on the immersion heater threads 'cos they can be an utter sod to get out later.

Thanks for that - it was the impossibility of removing the failed immersion heater that led to the leak which meant replacing the tank. To think that £140 could have been saved by a smear of copper grease!

Thanks again to all who replied.

It would be safer to say that £140 *may* have been saved by a smear . .

In some cases, it's virtually impossible to remove an immersion heater non-destructively after it's been in for a few years - whatever you do. Perceived wisdom (in other words, the general concensus in this NG ) seems to say that your best chance of getting it out without damaging the tank is to slacken it while the tank is still full, and to use impact rather than steady torque - in other words, hit a short spanner with a hammer rather than pulling steadily on the end of a long lever.

I have heard this cited many times on this group, and although it makes sense the idea scares the s*it out of me!

Just have all the stuff to do a drain down handy and ready for immediate use;!....

Another way is to heat the copper around the heater. The copper expands and it slips out.

That's what I did.

The reason why immersion heater spanners have short handles is so you use a hammer to break the seal rather than huge torque which will bend and possibly tear the tank.

That sounds like a good idea, but the tank is covered with insulating foam and the top of the immersion heater is of a much larger diameter than the threaded boss.

Also, is the boss not soldered in to the tank? In which case the application of heat might cause more problems than it solves.

The message from Tony Polson contains these words:

For all that, I've have a couple which resist brute force and ignorance

- two things of which I can supply a sufficiency.

You have cut away the insuation. Agfter spy it in via a gun.

I am on about a threaded immersion. I know what I am on about having done it many times.

Alas I cannot manage the former, but of the latter I have a glut.

;-)

You don't need to whack the s*1t out of it, just keep hitting moderately forcefully until it starts moving. Think of those guns fitters use in garages for loosening and tightening car wheel nuts - you're just doing the same job a lot slower!

Boss green: not what I'd use for cylinder threads. PTFE tape applied sufficiently thickly will give a good tight fitting which shouldn't come undone when you're tightening the compression nut.

I usually add a squidge of boss green to the washer - helps it not to leak and may make it easier to remove in the future. (I doubt copper grease is OK for use with potable water.)

The message from John Stumbles contains these words:

Who puts potable water in their hot water tank?

.. it is nevertheless considered to be potable from the perspective of materials and fittings used.

The message from Andy Hall contains these words:

I suppose in this one instance it might be a suitable place for PTFE tape then!