Cracked Unisiphon flange

[DRM]

Can anyone tell me if they know of any other WC flushing siphon manufacturer that is so concerned about damage caused to their product during installation that they have to provide two separate warnings in the installation instructions?

WARNING:
1. Hand-tighten the backnut and then add only a quarter turn with grips. The tightening torque must be less than 15 Nm.

2. Do not use any lubricant, grease, sealing compound, paste, flux or solvent to avoid damaging the product and invalidating the warranty. PTFE tape may be used on the thread.

WARNING: Hand tighten the back-nut. Only add a quarter turn with grips. The tightening torque must be less than 15 Nm.

BTW, can clear silicone sealant or Fernox LS-X cause damage to a plastic siphon?

Any information would be very helpful.

Thanks.

 

[Hot&Cold]

Its usually to do with large rubber sealing washers which need to be clamped in dry and not to tight.

Using lsx will act as a lubricant and can cause the rubber washer to slide around in between the clamping area and not compress in a uniform way,even push the washer or parts of the washer out of the fitting. It has to be assembled and tightened dry.

There is no need to use sealants on this joint and the warning's above are very good information.

Ptfe tape is mentioned and can be used on other threaded parts of the cistern if needed but not around any joints with rubber washers,its often considered a bodge job as it should not be required.

 

[DRM]

I reckon most plumbers know better than to over tighten a plastic part which is why I always smear LS-X on the inside of the cistern shell no matter which siphon or flushing valve I happen to be installing. As far as know no other manufacturer disallows this.

Pottery cisterns do not have uniform wall thicknesses and I have suggested that they replace the supplied thin solid rubber washer with a thick foam type washer that Fluidmaster use with their flushing valves. I believe this would be an inexpensive way of solving this cracking problem. It will be interesting to see if they change the washers that they supply in future.

I wish I still had the original instructions to see if the warnings are a new addition.

The other thing that they have picked up on is the traces of LS-X that I smeared onto the inside of the cistern before fitting the part (belt and braces). How this can have caused the flange to crack is a red herring.

The same thing happened on the same job a couple of years ago but it was discovered before there was much consequential damage done. When I saw the crack, I assumed it was a manufacturing defect and replaced it like for like. A big mistake that was!