Draining down hot water cylinder

[clive.r.long]

Hi,

I just need to check if I have understood this correctly and whether there are any risks or issues I need to be aware of.

As I understand, the water going through the hot water cylinder to the taps is supplied up the main through a tap to the cold water tank in the loft t hen down under gravity to supply the bottom of the tank through a gate valv e. If I want to drain the cylinder I shut off the tap on the side supplying the tank in the loft and shut off the gate valve supplying the hot water c ylinder. Then I attach a hose to the drain valve at the bottom of the cylin der and open the drain valve. Having shut off the gate valve the water in the cylinder wont be replaced f rom the tank in the loft. Is that it?

Thanks

Clive

[Bill]

In message , [e-mail] writes

If I understand you correctly there is no need to shut off the supply TO the cold water storage tank in the loft. Just shut off the cold supply TO the hot water cylinder FROM the storage tank. So just one valve to close. If it is a gate valve, when you open it again after your work open it fully and then back off a turn, this will give you 2 ways to turn it next time. They often seize and having 2 ways to turn to free them is better than 1

Why are you draining it? If it is to replace the electric heating element loosen this before emptying the cylinder, the tank is weak and the water inside gives it strength, without this it is easy to distort the tank.

I'm sure a plumber will be along in a while with more suggestions.

Have fun what ever you are doing. :-)

[John Rumm]

Yup, what he said.

Not all systems have a valve[1] between cistern and tank. In which case you can either tie up the ball c*ck, and drain the cylinder and cold tank, or better, block the outlet of the cistern using a rubber bung, or if you can't find anything better a carrot!

[1] and for those that do, its often a gate valve, which are frequently the spawn of santa, failing to turn off completely, and then the shaft snapping when you try to turn them back on and thus staying permanently nearly closed!

Note if all you want to do is stop hot water coming out of the cylinder, you don't need to drain it - plugging the feed alone will be enough for that.

[Tricky Dicky]

Gate valves are notorious for allowing a small trickle through no matter ho w tight you shut them, use the opportunity to replace it with a decent isol ator and then do as John has suggested. If your cylinder is an indirect one connected to the central heating that might need draining down too if ther e is no effective way of isolating the feed and return from the coil.

Richard

[Roger Mills]

Basically, yes - but as other have said, gate valves often don't seal completely - so a cork in the outlet pipe of the header tank[1] may be a good idea in addition. Or even instead of turning off the gate valve, just in case it fails whilst being closed or re-opened - which is always a risk.

Yet another alternative is to drain the header too, by shutting off its mains feed and then opening a hot tap until no more water comes out. You'll probably need to do this anyway if you decide to replace the gate valve with a quarter-turn full bore lever operated ball valve - which I would recommend doing.

As a matter of interest, why do you need to drain the cylinder?

[1] You'll need to reach down inside the header tank to do this. Remember to remove it again when you want the cylinder to re-fill!

[Tim+]

Um no.

An indirect cylinder heats the water indirectly though a heat exchanging coil. CH water and domestic HW do not mix.

Tim

[Alan Dawes]

If it's an old gate valve that hasn't been closed/opened in the last few years you may find it difficult to close particularly in hard water areas. Don't just use brute force you will very likely snap it. This can be due to slight seepage of water past the gland nut causing lime to build up as the water evaporates between the spindle of the gate valve, valve body and nut. Use a spanner to loosen the gland nut first before trying to turn the handle. If still no joy you could try removing the gland nut and spray the packing with lime scale remover, leave and try again. Still no joy - spray with penetrating oil - WD40 will do - leave and then try again. I'm lucky that I've not found a valve that cannot be shifted by doing this even the main stop c*ck to this house which hadn't been touched in 30 years.

NB If you do have to use lime scale remover, clean and repack the gland or, as I've done on a kitchen tap with a leaking gland nut, fit a suitably sized plastic/rubber O ring coated in silicon grease and tighten until no dribble of water. Better still fit a new stopcock.

There's a picture of the parts on the following page:

Alan

[Roger Mills]

Indeed. But the previous poster may have assumed that the cylinder was being drained in order to be removed/replaced (the OP didn't say) - in which case the primary circuit connections *would* also need to be disconnected.

[clive.r.long]

Hi

To clarify why I might needed to drain the hw cylinder. There is a tiny lea k from the cylinder that I can cope with with fresh towels and old sheets e very day. The old system is being replaced by a combie condenser. The plumb er who I trust won't be available to refo the system till the new year. I j ust need to know how to drain the cylinder if the leak gets worse.

The big cold tank in the loft (not the small header tank with the expansion vent pipe bent over it), the big tank has three outlet pipes from the base of the tank. One pipe goes to refill the indirect hot cylinder via the stu ck gate valve, I am guessing the other two pipes from the cold tank supply the cold taps and maybe toilet cistern downstairs. ??

So ... I am trying to buy a bung kit but they are out of stock locally. I m ight try as pipe bungs those flexible stoppers put on the top of a wine bot tle when opened ( I tend not to drain the whole bottle in one go nowadays). The aim being to stop the cold refill to the hw cylinder if i need to drai n the cylinfer. All of this is just if I have an emergency over Christmas a nd I won't have to pay hundreds to an emergency plumber to drain my hw syst em if I can deal with the immediate problem myself.

Thanks for all the contributions so far.

Clive

[charles]

On my cw tank the pipe to the HWC is too big for one of the wine stoppers.. Bungs are good,

[Thomas Prufer]

Carrot? Champagne cork, with the conical section cut from the top, and used upside down? Empty wine bottle, thickly wrapped with clingfilm and top-down? Wad of hemp twine?

You'll be all right, plenty of possibilities.

Thomas Prufer

[Roger Mills]

Thanks for the clarification.

Can you see where the cylinder is leaking? Is there an actual hole in the copper or is one of the pipe joints weeping - or even the seam round the bottom?

[Tim+]

If it was me I'd just turn of the supply to the loft tank, run it down to empty and then replace the gate valve. That way you'll be properly prepared should the HW tank leak worsen.

Of course, you'll still need to drain the HW tank to prevent a tankful of hot water leaking out if the leak worsens. If it has a drain c*ck near the bottom, use that, if not, you'll have to undo the top connection to the tank, poke a hose pipe to the bottom and syphon it out.

Tim

[John Rumm]

At last, a good use of a Brussels Sprout!

(if you have a gravity fed shower, then a direct feed from the cistern is also commonly done - usually tapped from the tank a bit below the outlet to the hot cylinder. That way if the cold cistern runs out of water, its the hot that stops first).

[clive.r.long]

Nope. No visible source of the water. Could be a pin hole or a crack in a s eam. The cylinder sits on the floor boards and the water just seeps out. Pr obably a greater amount is going into the ceiling void.

My worry is if I block all the pipes coming out of the cold tank in the lo ft and I open the drain c*ck at the bottom of the HW cylinder and that brea ks then I have a major flood on my hands. I wonder whether opening the top of the cylinder and syphoning will be safer.

Ta

[clive.r.long]

OK, some progress.

I have tied off the ball valve supply to the cold tank in the loft. I put t hree flexible bottle bungs in the three outlets at the bottom of the tank. I then flushed the loo and the cistern did not refill. I took out each bung in turn and on one of them I could really feel the water being pushed into the pipe and the cistern refilled. So I have left this pipe open at the bo ttom of the tank. I am going to let the use of the toilet drain the cold wa ter tank. I have two 250 litre water butts outside to supply cistern water if the cold tank empties. We are due much rain.

Now I see the pressure on the hot taps is low , due to one of the bungs blo cking the flow and I guess the water in the pipes supplying the hot taps wi ll empty quickly. I have fresh mains water supply in the kitchen which I wi ll heat and use for washing.

Once the hot taps no longer supply water my remaining risk is the remaining water in the HW cylinder which I guess syphoning out the top might be the best option. I am going to have a go early tomorrow. I will throw money at the plumber if I have a catastrophe but I guess I will have limited the pot ential flood to what is in the HW cylinder.

Ta

Clive

[damduck-egg]

You don't say where you have looked for a bung kit. If you haven't tried one already and have one close then yacht /boat chandlers often stock bung kits for stopping up inlets through the hull.

G.Harman

[clive.r.long]

Hi All,

The wine bottle stoppers worked fine to block the outlet pipes from the cw tank in the loft.

The square headed drain c*ck moved very easily, the compression fitting beh ind the drain c*ck was impressively robust so nothing came adrift when i lo osened the stop c*ck screw. The HW cylinder is emptying through a hose out into the drain. The cylinder seems to be taking a long time to empty but th e flow is slow and steady out of the end of the hose.