Problem connecting water inlet to toilet cistern ((HELP))

[jaba]

Hi and I really need some advice on this ASAP..

I had the end blow off the water valve in my cistern which would have flooded the place if I wasn't in.

I've purchased a replacement valve complete with the arm and new washer etc

When it arrived I could see that the thread end was much longer than the one I took off.
This is the bit that goes through from inside bottom of cistern to attach to water inlet.
I called the supplier and he said I would have to shorten the end if I couldn't move the pipe down. The pipe does a right turn through a wall so it can't be moved more that maybe 2mm at most up or down.

I cut the end to match the length of the old thread but it was still too long and up tight against the end of the inlet pipe olive! I couldn't tighten the plastic nut fully so the conical washer wouldn't seal, so I took off a bit more so all looked good.
Tightened up plastic nut and conical washer nice and tight (not too much)

BUT........ The metal nut will not tighten onto the plastic thread (I've really tried for over an hour)

Note. The inside diameter of the new valve pipe thread at the bottom looks about 1mm smaller! (is this the problem, it will not move down)?
And because I've had to cut the plastic thread down to size I think I'm stuck as the beginning of the pipe looks like it had before I cut it a very slightly bigger diameter.
This too is the same for the one I took off, but the old pipe is way shorter and still has the slightly bigger diameter for about 10mm inside the plastic pipe!

Should the top of the metal nut on the water inlet slide or tighten etc above the top of the olive?
(it seems to stop and not want to up any further!)

It seems to me because the old valve/pipe could move down on the olive by a few mm which was below the top of the olive the metal nut could catch the end of the plastic thread!

But the new plastic valve pipe thread will only sit on top/level with the pipe!!!

Old and new parts are made by Fordham with the curved arm to go around the syphon.

Any advice very welcome as I have no way of isolating the water to the toilet so this is a big problem now, no loo, sink or shower
Thank you..

 

[spraggo]

Hi jaba

You will note that the old threaded connection had a recess inside the pipe about 15mm deep to enable the existing copper water supply tube to slide up inside it. The new one also had this but,unfortunately you have cut this off. The only way to overcome this is to get a straight compression copper to female brass connector and screw this on to the plastic thread of the new valve, sealing it with PTFE tape. You may have to shorten this plactic pipe even more to get the connecter in. Hoping that you have enough thread protuding out of the bottom of the cistern to do this.

spraggo

 

[TicklyT]

It's worrying if you have an olive on the end of the pipe connecting to the float valve. The tails are usually made to accept a tap connector, not a compression fitting olive.

Normally a tap connector has a fibre or rubber washer to seal to the float valve / tap tail, and a pushfit / solder / compresion fitting on t'other end to connect to the pipework. There is no tapered seat in a float valve tail to compress an olive onto the pipe.

Cutting down the tail of a float valve or tap is generally a bad move unless you can get the end EXACTLY square, and extend the internal counterbore to accept the spigot of a tap connector.

Cutting the horizontal pipe, and fitting a flexible tap tail formed into a 270 degree bend may sort out yout problem.

Use one with an isolating valve, and you can restore the water supply to the rest of the house whilst you work on it.

 

[jaba]

Thanx spraggo & TicklyT

Yep spraggo I did see the 2 different inner diameters of the old valve. It's more like 10mm but this old valve hasn't been shortened!
I had to cut the end off down from 46mm to approx 30mm because the valve would not sit down on the washer inside the cistern. Of course I know now I was doing something I shouldn't have done but was assuming what was there was correct ooops..
Thanx for the tip, not sure I like the sound of using tape to make a water tight fit tho!

Funny thing is, as an emergency I stuck the old one back together and put it back on last night and the olive is watertight, not a drop lol I know it's not correct way but it seems to work.
I only have 30mm ish left on the valve thread so not much left on there now after it goes through cistern and the new conical washer is twice as thick as the old one!

--------------
TicklyT, yep I also spoke to someone last night and they said it should not have an olive on the end..
I see if I can pick what you guys suggest up today and hopefully make it work.
It would seem the old valve inner diameter is 16mm at the end.
If the new valve thread was the same length as the old one I think it would have gone on. The inner dia of the new valve is 15mm. But now the new one I've cut down to same length as old 30mm ish now inside dia is 14mm. No chance of that sitting over the olive at all, it just sits flush on top.

Yeah I know it was a bad move to cut the tread down, but the supplier said do it cos he assumed I had the standard tap! fitting I guess. But maybe he was wrong anyway as I would still have had the smaller inner dia of 14mm which is too small right!

Not sure if I can fit what you suggest "flexible tap tail formed into a 270 degree bend" as not much space but I'll have a look at doing that.
I'll try and upload pic so you can see dimensions.

I know it's not correct way to do things, but as the old one has never leaked.
What sort drill bit etc would you guys use (if you had to) to bore out the inner shortened valve thread?

The old valve inner is 15mm with a wall thickness of 2mm.
The new valve inner is now 14mm and 3mm thickness.
I think it unlikely I would be able to drill this, trying to keep it straight etc.
It would save me buying a new one and also take the inner dia back up to 15mm

Info; bottom of tank to top of copper pipe with nut is approx 16mm
Centre of coper pipe to side wall is 110mm
Centre of coper pipe to back wall is 20mm approx.

New valve thread length after cutting is 29mm
New valve thread inner dia 14mm
New valve thickness after cutting down is now 3mm (2mm before cutting)

Old valve thread length 30mm
Old valve thread inner dia 16mm (Lets it sit 5mm approx down on the olive)
Old valve thread thickness 2mm

Thanx again for the advice chaps. View media item 27771