Hot cylinder vent pipe

minimoog · 20 Apr 2008

I need to replace my loft cold water cistern as the existing is inadequate to supply the hot cylinder and shower pump I am planning. Unfortunately I cannot readily remove the old cistern and replace it as the access is so restricted, so the new tank will ideally go a few feet away where there's more room.

Can I re-route the hot cylinder vent pipe to discharge into a tank two or three feet away? I.e. is it allowable to curve the vent pipe so that it reaches the new tank, and if so are there limits on the degree of offset from vertical the pipe can be. I have read this

http://www.iphe.org.uk/databyte/tank_cistern_installation.pdf

and I understand the pipe must continue to rise until the point at which it discharges over the tank.

Thanks for any help.

leakydave · 20 Apr 2008

Why not add another cistern joined to your existing one to double your water volume? Make sure the new cistern doesn't just contain stagnant water, so use it to feed the shower, or take all the feeds from the old tank and put cold mains supply to the new one? Make sure any cisterns are insulated and on firm flat base, with insulation removed from underneath.

minimoog · 20 Apr 2008

I had originally intended to add a second tank solely to feed the cold side of the shower pump (cold supply to bathroom is currently mains). I'm concerned though that the inlet to the existing tank is directly above the outlet so aerated water entering the hot cylinder may be an issue. There's insufficient access to move either the inlet or outlet to the other end of the tank.

I was thinking that if I've got to put a new tank in anyway I may as well size it for both hot and cold feeds and abandon the old one. It might be possible to join the two tanks though and leave the vent where it is although again access will be a problem - I'll have a think about that.

twgas · 20 Apr 2008

minimoog said:
I need to replace my loft cold water cistern

read this //www.diynot.com/forums/viewtopic.php?t=132517

be warned

minimoog · 20 Apr 2008

That's what overflows are for isn't it?

Gunslinger · 20 Apr 2008

just read the PDF file, some good info in there for us DIY'ers, however, looking at the end of the text on the first page it looks like there is a little missing, and the sentnaces dont blend together too well, and seem to stop abruptly at the end of the second column.

minimoog · 16 May 2008

Thread resurrection...

Project has been on hold for a few weeks but it's crunch time now.

Are there any show-stopping technical or legal reasons why I cannot vent a hot cylinder to a loft tank which has a mains supply and overflow but which is otherwise unused? I need a new tank to feed a bath/shower pump but cannot fit it anywhere near to the vent.

I cannot link the two tanks because I want the new one to be higher to increase head thus flow to the pump. Old tank cannot be moved at all.

System would look like this

I don't like the idea of a tank of stagnant water at all but I can't see another way around this problem, which is basically caused by there being no loft above the centre of the house (shaded bit) and the old tank being wedged into the eaves behind some roof timbers making swapping it out impossible.

As ever thanks for your help...

sooey · 16 May 2008

Going by your picture, the water level in your new tank is virtually the same height as the vent.

minimoog · 16 May 2008

Oops yes I see what you mean

Thank you for that!

I'll put the new tank at the same level as the old and tee into the existing supply to the cylinder from the old tank as leakydave suggested above. Fingers crossed flow to the pump will suffice.

waterworks · 16 May 2008

Hi reading your thread there is no reason why you can't run your vent horizontally across to new tank position, as long as it has a rise towards the new tank, is well clipped to prevent it from sagging, is insulated to prevent freezing.

When you read in books etc about vent pipes to rise vertically to point of discharge above tank this means that it should not go back down hill not that it needs to be only vertical, in multi storey installations it is quite normal to connect all open vents from all the flats into one large horizontally run pipe to discharge to tank.

ChrisR · 16 May 2008

Are there any show-stopping technical or legal reasons why I cannot vent a hot cylinder to a loft tank which has a mains supply and overflow but which is otherwise unused?

Breaches about 3 water regs!

waterworks · 16 May 2008

I agree with last post, forget the idea of leaving vent above redundant tank.

Also make sure you comply with regs buy Byelaw 30 kit as well as new tank, make sure when using tank to feed both hot and cold that the outlets at the bottom of tank aren't at the same height.

ie make sure the cold feed to the cylinder is higher so that the hot water will stop before the cold if the supply to tank is interupted so you can't get scalded.

ChrisR · 16 May 2008

Byelaw 30???!!!
Ahem Water Regulation 16

waterworks · 17 May 2008

Okay your right ask for a
Schedule 2, section 7,paragraph 16,G16.13/R16.13.1/2/3 kit

minimoog · 19 May 2008

ChrisR said:
Are there any show-stopping technical or legal reasons why I cannot vent a hot cylinder to a loft tank which has a mains supply and overflow but which is otherwise unused?

Click to expand...

Breaches about 3 water regs!

Glad I asked then!

I came to the conclusion over the weekend that I can in fact take the vent across the void above the bathroom to the new tank and keep it rising all the way to the correct height above the new cistern as per the above installation guide. So I'm binning the old tank completely.

Got a screwfix 50 gall tank with all the bylaw kit included and have plenty of pipe lagging for the vents and supplies to go from the tank all the way back to the airing cuboard.

Have installed feed pipes from cistern down to pump and hot cylinder in single sweeps of 22mm plastic (no elbows or owt) so flow should be decent - cistern is now 2.7m above the pump and cylinder. Hot take-off from the cistern is an inch above the cold.

Have made up take-offs from pump with full bore lever valves with auto air vents at high point, so hopefully I'm getting there!

Main issue next is drilling the hot cylinder for the Techflange to the pump...

Thanks for all the help chaps.

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Hot cylinder vent pipe

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