Hot Water Cylinder Replacement

[MrRee]

Hi all - searching the net for advice on how to do the above!!

The plumbers want £300-£500 to swap a cylinder!!!

I have NEVER done nowt like this before but am a Qualified Engineer, 5 years apprenticeship in Mechanical Engineering and now a Specialist Design Engineer ............... so, I understand things and want to give it a go!!

Where do I position the 3-way valve to drain down?? Do I REALLY have to drain down ALL the radiators??

What is the sequence for filling it all back up and bleeding it all??

How long should I allow myself? About 4 or 5 hours??

All help welcome, thanks!!

MrRee

 

[alexnic]

It's not that difficult, I replaced mine a few months back ...

Your hot water to the radiators don't go thro' the cylinder coil that's only to heat the domestic hot water.

I closed off the 3-way diversity valve so there would be no water flow to the cylinder + the feed from the tank then drained it. I think I did drain the system off to below the level of the cylinder to ensure the coil inside was drained off (Indirect type)
After that its a straight swap. I never had much problem with bleeding the system....probably just lucky

Took the best part of the day for me but then again I'm a Spark, not a plumber!

 

[ChrisR]

You need to stop the supply to the HW cyliner . The valve MIGHT work but I'd be surprised, so would drain the big CW cistern . Via bath tap usually. Then drain cylinder via its drain cock which should be on the input pipe at the bottom. Again, that might not work, so you'll hvae to drain via the hot tap until the water stops - but then the cyl will still be full. That means siphoning through the top connection on the cyl.

If the drain cock does work, you'll still have a fair bit of water in the cylinder. An aquavac is very useful! Leave the old cylinder on the pavement and someone will relieve you of the problem of disposal!

Drain the heating to below the level of the coil.

Usually means tying up the ballvalve(s) on the cisterns in the loft.

Withthe new cylinder it is often easiest to assemble some pipework on it before you put the thing in place.

You may have an air bleed point on the top of the primary (coil) connections for the heating, and you may end up with an air lock in the hot and/ or cold cistern fed pipes. Shove it with the mains!

Typical plumbing job - not difficult but a number of complications can crop up