DIY Doctor

What to Expect When Fitting new Hot Water Cylinder

Postby Summat » Mon Dec 28, 2015 11:13 am

First post: A bit of background - male 46 year old, reasonably handy with most things but I hate plumbing. I much prefer to "have a go" if something is achievable and legal, but can resort to tradesmen when things are clearly outside my scope.

Right, have a 18 year old house with a gas system boiler in a cupboard in the kitchen. This feeds a Y-plan heating system with an indirect vented cylinder. For a while now there's been a sporadic leak from the overflow pipe on the heating F&E tank, and I've observed a trickle from the HW tank ball cock/valve, and a warm current from the lower feed to the CH/Heater system - all, I believe, suggestive of a failed coil in the HW cylinder.

I plan to have a bash at replacing this - it's probably easier than the necessary tidying up of the house before getting a plumber in, and, my one approach to a plumber has suggested that they're entitled to a holiday period as well (fair play).

So, I'm looking at one of the national suppliers of DIY bits that are open this Christmas period, who started life fixing screws. They offer a similar sized tank, 400mm x 1050mm (mine: 143cm diameter I've gauged from the existing cylinder circumference divided by pi, minus 6cm for the two walls of insulation gives me a pretty precise 400mm diameter. Height was rack of eye with a tape held against the cylinder wall from base to approx height of lower face of the exit nut. A rough measure like this seemed to indicate the preferred size of 1050mm so I'm fairly happy I've got the right size. Indirect heating, so pipes heading through the side wall.

All existing pipework is 22mm, soldered, apart from gate valves etc. which are compression. Feed into the bottom, and flow from the top look to be connected to very short stubs off 22mm 90 degree elbows (the ends of the elbows are very much against the nuts on the tank). The side ports - the top one is very much the same as the HW side, the lower one is peculiar to me as it's a straight pipe run, but with a sleeved coupler (my words), which is soldered over the 22mm, and reduces back to 22mm (if that makes sense) before entering the nut.

It's all these unions that are causing me some consternation - this is one job that once started I need to be able to complete within the day (I'm married, and intend to remain married).

If I buy a replacement copper cylinder, I've found a RM cylinder 1050x400, which the national DIY supplier includes customer comments of "doesn't include compression fittings". RM's website is undergoing revamp, and I can't easily find any product details of the copper tanks, other than a comparison with their stainless range. It does suggest 1" bsp male/female fittings, but not indication of which, and on which ports.

So, finally to my question, apart from the cylinder, and a new immersion heater, immersion spanner, and on the faultless(!) logic that this should be a plug-in like-for-like replacement, what fittings could I be expected to require to order, prior to me cranking the first nut? Should I be sourcing these, rather than transfer off the old tank (I'm not going to jeopardise the job for a few quid), and what the hell is an Deleted or Deleted flange, when it's at home? (for reference, existing pipework is a single pipe that much later tee's off to the HW supply to the taps).

Any info, gratefully received.
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