Replacing hot water cylinder

[njmorrison]

Hello all, I'm replacing an indirect hot water cylinder which only has about a metre head, it's in a flat. The hot water draw off in the old cylinder is positioned about 10 inches below the top of the cylinder which goes to a pump because of the low pressure and the pipe out of the top of the cylinder is for expansion only. Can I have my hot water draw off on the new cylinder from the top of the tank as part of the expansion pipe as normal or does the draw off need to be below the expansion because it's feeding a pump?
Wanted to avoid cutting new hole in cylinder for adding an essex flange!

Please advise

Thanks

 

[Plumbstar Tom]

Hi NJMorrison

Preferably i'd still go with the essex flange as the prefered method but if you still wish not to do this take your draw off a few inches below the expansion T this will avoid air getting to the pump

 

[njmorrison]

Thanks for that Tom

Cheers

 

[Bernie2]

No I would leave it the way it is. The pump may draw off water faster than it can be replaced and so draw down air into its inlet if you use the expansion pipe.

 

[NickH]

I suppose the problem is that as the top outlet feeds nothing then your heating the water in the top of the tank and never using it, a waste of energy. Your new cylinder will probably come with a secondary tapping in the side near the top but again you wont use the water at the top. You could use a surrey flange which wont draw from the very top but about 6 inches down so you only lose the top of the dome. Depending on how keen you are you could try teeing of the vent first with a mind to altering it if you have a problem with air drawing down the vent. You could also think about increasing the cold feed to the cylinder to 28mm (if its not already).
I've fitted a horizontal cylinder in an attic with less than a metre head. I used a 28mm cold feed and fed two showers from it. One via a surrey flange to a 2.5 bar pump and one tee'd of the vent to an Aquastream with a built in pump. I've had absolutely no problems with air draw down.

 

[njmorrison]

Thanks guys, I think I'll go with the essex flange. I think it was probably done like that originally because the cylinder couldn't fill quickly enough if it was drawn off the top!

 

[Plumbstar Tom]

Essex all the way

With a surrey flange you may find air is still drawn in and a Surrey flange is also restrictive

 

[NickH]

I think I would be tempted to try a Surrey first and see how it performs, if any problems alter it to an essex. Would only take half an hour or so to redo it all and you can use the surrey again elsewhere.