Cistern fill valve problem

[Faz778]

Hi folks. Hope you can help.
I recently bought a new toilet pan and cistern online. It came with a blue and white fill valve, the compact type, not a ball cock like in my old cistern. The new cistern isn't big enough for a ball cock type.
The problem is that the fill valve is almost totally restricting the refill and the cistern is taking about 30 mins to fill! I removed the flow restricter so it's not that.
I went to Plumbworld and spoke to 2 plumbers who were in buying stuff. They recommended trying a Fluidmaster fill valve so I tried one of these and the issue is the same if not worse, virtually no flow. When I take the top cap off the valve there is a good flow but as soon as I replace the top cap it stops again.
My supply is low-ish pressre from a tank but not very low and the Fluidmaster fill valve states that it is suitable for low pressure systems.
I had no problems with my old ball cock system so surely tbe pressure can't be that bad?
Any ideas???

 

[Armo74]

Have you checked the water level in the tank?
Is your hot water flow ok?
Check any other valves if you have any, like isolation valves you may have one partially closed.

 

[Faz778]

Hi. All valves are fully open. Flow from hot and cold taps is good. The flow from the cistern supply flex hose is good too, about as good as the cold bathroom tap which also comes from the tank. Someone has suggested I try a Torbeck fill valve? Good idea?

 

[Armo74]

Have you used a flexi hose for the cold connection to the cistern?
Have any alterations been made to the pipework to accommodate the new toilet?

 

[Faz778]

I put a new 500mm flexi in for the cold cistern supply. I did this cos the filler hole is on the left if the cistern whereas the old one was on the right. Other than that, no alterations.

 

[Faz778]

Fitted the Torbeck valve and it works a treat. It would seem that the Fluidmaster isn't suitable for a low pressure supply after all.