check valve on hot water expantion pipe/overflow ?

[blackplasma]

not 100% on terminology but im refering to the pipe that t's off from the hot water out at the top of the cylinder and goes up to an inverted u shape above the tank in the loft,
i am told it allows air to escape from the hot water storage and allows overflow due to expantion?!

can i fit a non return / check valve to this?
reason: to stop air being drawn in to the hot water supply by a shower pump

i also aim to fit a check valve after the pump t to stop air being drawn up from the taps in the rest of the house

 

[combispecialist]

no valves at all are allowed on this pipe

 

[picasso]

if you want to stop air being drawn into the cylinder, increase the feed pipe to the cylinder, what pump have you fitted and how big is the cylinder and tank in the loft ?

 

[TicklyT]

No, you can't fit a check valve on the expansion pipe.

If you did, have you considered what would happen when you run the pump?

(The hot cylinder could collapse.)

What would happen if the check valve jammed shut?

(The hot cylinder could explode.)

If the pump is drawing in air via the open vent, it's either because the cold feed to the cylinder isn't capable of refilling the cylinder fast enough, or because the feed to the pump is wrongly positioned.

 

[tamz]

can i fit a non return / check valve to this?

No. There should be no valves of any kind on this pipe. Doing so is dangerous. A non return valve fitted in this instance would probably lead to the collapse of the HW cylinder.
You should use an Essex or Surrey Flange for connection of the pump.
You could also increase the size of the feed pipe to the cylinder.

 

[blackplasma]

ok thanks for the advise (which i will be taking)
basically i baught the wrong pump and cant afford to change it!
i baught a salamander right pump which aparrently needs its own feed off the boiler, i dont think ive got the skill to do this so by cutting off the expantion pipe and the flow down stream of the pump i would effectivly give it its own dedicated feed without any air being able to come in from any where!
i should have baught a ct 50 which can be instaled in the position i need to without problems!

solution:
fit it like a ct50 with a check valve after pump to stop any air from taps but leave expantion pipe open, if it draws in a bit of air and the pump fails in a few months then oh well off to the shops for a ct50, if it survives.. .happy days!

with regards to the pipework ive got 22mm coming from the header tanks which is 2 side by side, both knee hight and 3 or 4 foot diameter, and the hot water cylinder is waist high! feed to the pump is 22 mm apart from an inch at the pump end and the rubber tail