Help with pipe connection sizes.

[scudo12]

See attached image.

I need to connect a toilet cistern to the mains inlet, Plumber got all the pipework in place with isolating valves, I now have to connect it.

A. elbow joint, would this be a 3/4 inch female to male and would I use PTFE tape to seal it on the cistern side? The flexi hoses appear to come with a rubber washer inside.

B. Would the flexi hose be 3/4 inch female to female?

Both the mains inlet and the cistern are 20mm OD.

 

[ianmcd]

who knows where you got that idea from but totally wrong just use a 15mm flexi hose

 

[scudo12]

Will a 15mm flexi hose fit on to the 20 mm fittings?

 

[denso13]

Will a 15mm flexi hose fit on to the 20 mm fittings?

Yes

 

[ianmcd]

As said yes it will

 

[scudo12]

Am I confusing the end fittings thread diameter with the diameter of the flexi pipe?
In other words a 15 mm flexi will have end fittings to fit the 20mm outlet.

 

[denso13]

Am I confusing the end fittings thread diameter with the diameter of the flexi pipe?

The threads/fittings in you first post are 15mm internally.

 

[terryplumb]

The thread on your WC filling valve ( float valve ) is 1/2 inch BSP thread. The thread on your isolation valve is the same. The flexi hose to join the two directly would be 1/2 inch bsp ,both ends. ( I wouldn't recommend you use that directly onto an isolation valve though ).The flexi hose in your pic has a compression fitting at one end,should you wish to use that type ,you would need a 15mm compression to 1/2 inch bsp flexible hose. The compression end would need a short piece of 15mm copper tube fitted between it ,and the isolation valve ( and an olive and nut ,as none showing in your pic )

 

[terryplumb]

Yes

It won't if its 15 mm compression fitting at both ends.

 

[scudo12]

OK does this image now make sense?

 

[terryplumb]

Yes it does. Is your cistern concealed ( fitted inside a cabinet ), with a side entry float valve ? If so ,is there enough space between the cistern and cabinets side wall to accommodate the angled flexi ?

 

[scudo12]

Yes it is concealed, out of interest why shouldn't I "The thread on your isolation valve is the same. The flexi hose to join the two directly would be 1/2 inch bsp ,both ends. ( I wouldn't recommend you use that directly onto an isolation valve though ) put it directly on to the isolation valve as I thought the rubber washer would seal it.

 

[denso13]

Or take the isolation valve off and replace with this https://www.screwfix.com/p/flexible-tap-connector-with-valve-15mm-x-x-300mm/3558G

 

[terryplumb]

The iso valve does not have a flat mating surface for the rubber washer ,but is tapered on it's inside edge to accommodate the olive, so over tightening onto a rubber washer can split the washer.

 

[terryplumb]

Or take the isolation valve off and replace with this https://www.screwfix.com/p/flexible-tap-connector-with-valve-15mm-x-x-300mm/3558G

Its a side entry valve ,on a concealed cistern . That hose is likely to bend and fail.