Toilet Cistern not filling

fitzie79

I'm in the process of installing an en-suite in the upstairs bedroom. We live in a dormer with 2 bedrooms downstairs and 2 upstairs. Having connected the cistern on Friday I've noticed something strange. The cistern is fed from the pump which is located downstairs (I think because the tanks are in an attic space that is at the same level as the upstais cinema en-suite) and when I flush the toilet the cistern doesn't fill. It appears as if the pump isn't detecting that the cistern is calling for water. When I run a tap downstairs the pump kicks in and if I then flush the toilet the cistern fills normally. I don't think the problem is with the cistern itself and there is definitely water at the inlet so doesn't appear to be an air lock either. Any ideas why the pump isn't kicking in when expected?

K.Flyer

Most likely you have a positive head pump, you will need to have it changed out for a Negative Head pump.
Negative head pumps have a pressure switch that detects the drop in pressure and activates the pump.

corkgsxr

Post a picture of the fill valve.

Calahonda52

what else is in the ensuite: shower, whb, bidet?
What happens when u use them?
Neg head pumps are big mula so is there anyway you could raise the attic tanks enough so as the top of the water in the attic tank is above the inlet to the cistern

Wearb

Why not put a small expansion vessel at the feed side of positive head pump. I think it could be plumbed in to provide the start up flow needed.

Perhaps I haven't thought this out fully, but it seems workable.

K.Flyer

Some positive head pumps can be converted somewhat to negative head. A universal pcb, non-return valves and a couple of small vessels, and pressure switches T-eed onto the outlet pipes will do the trick.
But its best to do it with brass bodied pumps as they are better designed for the static pressure build up.

fitzie79

Calahonda52 wrote: »

what else is in the ensuite: shower, whb, bidet?
What happens when u use them?
Neg head pumps are big mula so is there anyway you could raise the attic tanks enough so as the top of the water in the attic tank is above the inlet to the cistern

Nothing else plumbed in yet but there will be a sink and shower. Both of these are fed from the pump as well.

Raising the cold water shower tank in the attic is not an option due to the height limitations in that space. The hot water tank can't be raised by much more than a few inches either

K.Flyer

fitzie79 wrote: »

Nothing else plumbed in yet but there will be a sink and shower. Both of these are fed from the pump as well.

Raising the cold water shower tank in the attic is not an option due to the height limitations in that space. The hot water tank can't be raised by much more than a few inches either

Then you Will be needing a Negative Head Pump. Because of you configuration I would recommend that you get a Stuart Turner unit. The reason I say that is because, in your situation where the shower head and possibly the taps are going to be above the top of the water storage tank, the Grundfos pumps can develop a problem where the pump does not come on straight away when you turn on the tap or shower and at times the delay can get worse over time. Its a problem with the pressure switches on the pump, which, as far as I know, they still haven't resolved yet. The Stuart Turners don't have this problem.