Hot water booster pump sucking CW through vent?

[gspace]

Hi all,
Thanks for advance for any advice you can give me.

I have a vented gravity system with a HW tank on 1st floor and 1.0 m header tank in the loft. Due to poor HW pressure in all outlets, I've recently fitted a Stuart Turner Monsoon Universal Water Pump for Single Water Supply with 3.0 Bar Performance . For info, this is nominally designed as a whole house pump and not a shower pump.

I fitted the pump on the outlet of the HW tank by diverting the flow through the pump on the vented outlet at a level 0.5m below the HW tank, i.e. after the tee that opens to the vent. The problem I have is that it seems the pump is sucking through cold water from the header tank and very little hot water (if any) is being sucked through from the tank (note that the vent is immersed in water in the header tank). In other words, the pump is working fine but it is delivering cold water sucked through from the header tank.

When I read the installation instructions, I did wonder if that would/should happen. Surely, if you're sucking water at higher pressure than the HW tank head pressure, it will also suck through the vent. Has anyone expereince this before and can tell me how to fix it? I have thought about a surrey valve on the vent above the tee from the outlet but I'm not sure this is allowed?

Thanks for your help,
G

 

[CBF]

yes a surrey or essex flange would be the correct way but thats not your prob, the prob is that your vent pipe in the roof is under the water level & it shouldn't be the pipe needs cutting off so it goes into the tank lid but nowhere near the water level, however doing it the way you have might still draw air down the vent

 

[gspace]

yes a surrey or essex flange would be the correct way but thats not your prob, the prob is that your vent pipe in the roof is under the water level & it shouldn't be the pipe needs cutting off so it goes into the tank lid but nowhere near the water level, however doing it the way you have might still draw air down the vent

Thanks CBF. I'll do that with the vent. However, like you say, it could still suck air down. Any ideas how I can stop that?