Draining a cylinder

[Big G]

Apologies if this has been covered before, I have looked but couldn’t find anything.

The existing central heating system in our house leaves a lot to be desired. Pumped central heating and gravity domestic hot water. The problem with the hot water is that the cylinder is about 12 foot away laterally from the boiler and piped in 22 mm pipe rather than the recommended 28mm. The result of this is that the only way for us to get a cylinder of hot water is to leave the water on ‘continuous’ otherwise it air-locks. Even then, the hot water from the boiler flows via the ‘return’ and returns via the ‘flow’.

My solution is going to be to change the system to fully pumped. While I’m playing around in the airing cupboard, I thought that I’d change the cylinder into a slightly bigger pre-lagged jobbie.

The problem is the cylinder does not have a drain off fitted to it. I’ve thought of various ways of draining the cylinder and my thought is to screw one of those self tapping valves into the cylinder supply pipe and connect a hose pipe.

Anyone know of an easier method?



Many thanks in advance.

G

PS – I’m a DIYer so will be easily baffled by complex plumbing terms.

 

[weareleeds]

To drain cylinder empty tank by running off hot water then undo top cylinder connection stick about 2ft of 15mm copper into a hose pipe then feed into cylinder to bottom. Take other end of hose to drain outside stick in gob & suck hard for a few seconds to start syphoning. Dont forget to let planning control know you are changing cylinder etc & make sure you pipe it up correctly or your system will pump over or pull air in causing severe corrosion problems

 

[ChrisR]

my thought is to screw one of those self tapping valves into the cylinder supply pipe

If you can find one of those which fits 22mm, let me know where I can buy and I'll send you money!

A standard move which works fine and is cheaper, is to put a pump on the HW cylinder primary loop. Couple of things to watch out for - is the current Gravity loop off separate boiler tappings from the CH ones?
Next question, how far apart are the connections on the HW cylinder where the primaries go in?

(Primaries are the pipes from the boiler)

 

[Big G]

Thanks for the replies.

I checked last night and my boiler is a Glow-worm ultimate.

There are installation instructions available on the net which mention about where to place the pump in relation to the feed and expansion pipes (seem to remember that they need to be close coupled and a bypass fitted). As the feed is on one pipe going to the cylinder and the expansion on another, a fair amount of pipework re-jigging is going to be needed so I’m not too bothered about the fact that the new cylinder will not be a perfect match.

Also, I know that the gravity flow and return will need capping.

One thing that has bothered me is the comment about building control. I never knew that I would have to advise anyone that I was changing the cylinder. Is this because the new cylinder will be bigger and hence heavier or is it just the norm now? Does this mean that I will also have to change the header tank to make it bye-law 30 compatible?

Again, many thanks for the replies.


G