Fitting fluidmaster valve to attic tank

[Chris]

I tried replacing an old-style ballcock valve with a quiet fluidmaster side fitting float valve to reduce refill noise. Can someone please explain how a reliable seal can be obtained? I fitted a 1/2 inch quad plex pipe into the valve with a fibre washer. I then hand-tightened according to the instructions (as hard as I could to be on the safe side). This seemed to work until I turned the mains on fully and tested the valve on/off a few times and the service pipe just popped out of the valve fitting. I'm pretty sure I had the plastic nut correctly threaded all the way onto the plastic thread on the valve. I understand how standard compression fittings work, i.e. the insert fits into the pipe allowing you to tighten the metal ring onto the pipe without the pipe caving in, then the metal ring forms a tight seal between the nut and the connector. With just a fibre washer in place of the ring I just don't understand how this can work with 100% reliably with no chance of the service pipe popping out of the fitting.

I saw no reference to high or low pressure in the installation instructions but it is supposed to be able to work in an attic storage tank, which I presume will almost always be at mains pressure. The instructions didn't have any reference to any other rings or anything so I have no idea what I did wrong. Obviously I don't want to flood my house so I won't try a stunt like this unless I'm certain it's completely safe!

Thanks in advance for any assistance. Chris.

[Andrew Gabriel]

I'm having difficulty picturing what you're doing, but it sounds like you are somehow trying to connect up the pipe directly without using a 1/2" tap connector. Maybe you discarded the tap connector with the old ball-valve? The fibre washer is to seal against a tap connector. Here's an example tap connector with a pipework compression fitting:

and search for item 18526

[Chris]

Hi Andrew, Thanks for the reply. To clarify my post I'll refer to the diagram http://84.203.164.145/fluidmaster.jpgThe supply line is my quadplex mains feed. The 'tap connector' is a 1/2" compression nut.This is my mistake, it looks like a compression nut in the diagram but the picture of the tap connector you referred to looks very different. The 'washer' is a fibre washer.

The 'Shank' fits through the tank wall and I was sitting the service pipe directly into it and tightening the compression nut onto it with the fibre washer inside.

In hindsight I can see that this couldn't possibly work reliably under mains pressure but the installation instructions are really crap, the diagram is very misleading IMHO. I guess they are assuming the installer is a qualified plumber which is dangerous for something marketed as a DIY product.

Thanks a lot for the advice,

Cheers, Chris.

[Andy Hall]

On other tip (once you have the correct tap connector) is to leave the locknut of the valve loose while you locate and screw the nut of the tap connector onto the shank of the valve. Plastic threads on these valves are not very substantial and it's very easy to put the nut on cross threaded if the pipe is not in perfect position and alignment. The result is stripping of the thread and then the valve is destined for the bin. Having it loose to begin with allows you to align the pipe and shank and screw on the tap connector nut - finger tight. Then tighten the locknut and finally the tap connector nut.