Problem with toilet fill valve

[ProDave]

I'm re fitting a new bathroom in a flat. Trying to use as much of the existing plumbing as possible, and I have encountered a problem with the toilet fill valve.

The old toilet was filled with water from the cold water header tank, and as that header tank is on a stand above the hot water cylinder in the adjacent airing cupboard, the water pressure is extremely low, about 5ft of head.

The old toilet had a conventional float valve. The new one has a bottom entry Torbeck valve, similar to Screwfix part number 75136

The problem is firstly the fill is extremely slow (much slower than the old toilets fill valve, which was already pretty slow), but when full it does not shut off, in spite of the float floating up as far as it can.

Am I right in saying these types of fill valve won't work on such low water pressure? I have removed the flow restrictor which the instructions say to do for water pressure below 1 bar.

If this is the wrong type of valve for this application, what can I use instead. I really can't see that there is enough room in the small cistern for a conventional float valve.

The only other (unquestionably better) option would be to re plumb to get mains water to the WC, but everything is boxed in and it would be a major job to gain access to feed a new pipe, so that really is a last resort. I would prefer to find an alternative fill valve that will work on this very low pressure.

 

[Lurch]

I take it you can;t fit a conventional float valve in the new cistern?

 

[ProDave]

I take it you can;t fit a conventional float valve in the new cistern?

Not enough room in this modern tiny cistern.

Another forum has recommended a Fluidmaster valve, so I've ordered one and I'll give that a try.

If that fails, then it's down to trying to find a route for a new pipe to get mains pressure water to the cistern without completely demolishing the bathroom. At least with cables you can pull them through some tortuous routes, but you can't do that with pipes (well you can, but I don't like plastic pipe, I prefer to plumb in copper)

 

[Lurch]

Nothing wrong with plastic pipe. I'll generally use copper where I can but plastic does get used quite a bit, especially in situations such as you describe.