tapping into vent pipe?

[missmouse]

Hi, I have just fitted an Aqualisa shower in loft above shower (as recomended) The pump unit is (just) below the base of the cold water tank (as permitted) & I have tapped into the cold feed from the tank & also the hot water expansion pipe that loops over the top of the cold tank. This was just for convenience. The shower works great except when I run another hot tap in the house at the same time when the shower splutters, obviously starting to suck in air from the vent pipe.
Is it ok to fit a one way valve in this pipe or must I run another pipe to tap into the hot supply further away from the vent?

 

[thanks in advance]

i am not an expert but it sounds like there is no head of water in the vent pipe and when hot tap and shower in use,it is pulling air through the open vent.
usually for safety and best use most pumps need independent hot and cold water supply to pump.
ie.cold from tapping in cold water storage tank.
hot from cylinder via a surrey or essex flange.
what does the aqualisa instruction book say,what model aqualisa pump is it.
had this fault with a monsoon pump in a house i had years ago.
only fit a non return valve if you want a disaster.
has the earthing/bonding been checked,yes i know its all a drag but these days its all safety related.
good luck.

 

[Softus]

...I have tapped into the cold feed from the tank

This isn't what Aqualisa recommends!

...& also the hot water expansion pipe that loops over the top of the cold tank.

Nor is this, and you're about to wreck your new pump.

This was just for convenience. The shower works great except when I run another hot tap in the house at the same time when the shower splutters, obviously starting to suck in air from the vent pipe.

Obviously.

Is it ok to fit a one way valve in this pipe or must I run another pipe to tap into the hot supply further away from the vent?

Neither - do what the manufacturer recommends. And to save you looking, it recommends taking a dedicated cold supply from the cistern and a dedicated hot supply from a special flange fitted to the DHW cylinder.

 

[gas4you]

I would also check installation position. usually they should be installed lower, ie next to the hot water cylinder in airing cupboard, so in effect they are 'pushing' the water rather than 'pulling'.

 

[Softus]

Usually they are, but at the foot is the CSS is expressly permissible by some pump manufacturers.