HW Booster drawing air from vent

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Hi all,

I've fitted a Salamader RP120SU hot water booster. And its sucking air/water from the vent pipe. Any suggestions how I can fix this? I've extended the vent pipe into the header tank so that it ends about 2/3 down into the tank water, this is just to allow me to run the pump without drawing air and damaging the pump while I work out whats wrong, but I'm not getting anywhere.

Setup is all in one cupboard, flat roofed dormer so no loft.

90 litre cold water header tank supplied by 3 bar cold mains from 22mm inlet pipe and 3/4" part 1 float valve. Tank is sited on a shelf above hot water cylinder. When pump runs, the water level drops about 1/4 before float valve is open enough to maintain water level in header tank.

Vented hot water cylinder, 22mm pipework between header tank and cylinder inlet.

3/4" connection off top of cylinder, fitted with 3/4" Warix flange. 22mm vent pipe to header tank off side of Warix flange, 22mm feed pipe to pump inlet off top of Warix flange.

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Is the feed & expansion tank of the correct capacity, and is the base of it above the minimum 1.2 metres specified by Salamander?

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550mm height from horizontal vent takeoff on flange to bottom of tank as per your diagram. 950mm takeoff to water level in header tank. No room in cupboard to move the tank higher and flat roof, so thats all there is. Hadn't seen a diagram with that dimension on it, that explains a bit.

So solutions? Essex flange? A plumber had a quick look when he was passing and suggested either an essex flange or run the vent horizontally around the edges of the cupboard before rising it to header tank, I can't understand what that will do but he says they used to do that all the time and it worked?

If I go essex flange, apart from being a bit more work to fit the flange, any disadvantages I might find?
 
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550mm height from horizontal vent takeoff on flange to bottom of tank as per your diagram.

There you go then, the diagram says it should "Never less that 1.2m" You would probably be best asking Salamander the question regarding any possible alternative installation methods.
 
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You have come off the top of the flange to the pump it should be the other way round. Out the top of the flange should be your vent and the horizontal outlet of flange should go to pump.
 
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Hi Exedon your totally right didn’t even realise when I first looked and read the question.
 

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