Where do these rubber washers go?! Thomas Dudley Turbo Edge

[Chicken_Satay]

The diagram below shows a "low level" and a "high level" rubber washer.

What am I supposed to do with them and where do they do?

I think one of these (or both?!) get pushed onto the flush pipe and then I need to use the locking nut to screw them tight to the threaded part at the bottom of the sypon. I don't think it'll seal/fit properly with both of them... Which of the two do I choose?

Does anybody know where they go?

It's a Thomas Dudley Turbo Edge Syphon.

[GasEngineer]

Do you have a high or low level cistern (connected by a short or long pipe to the pan) or is is a close coupled type that sits directly on the pan?

If close coupled you don't need the washer and nut, otherwise use the washer as specified for high or low.

[Watcher of the skies]

I'm not a plumber, but I'd guess that you use the low level washer if you're mounting the cistern as close coupled and high level if it's high up wall mounted.

[Chicken_Satay]

GasEngineer said:

Do you have a high or low level cistern (connected by a short or long pipe to the pan) or is is a close coupled type that sits directly on the pan?

If close coupled you don't need the washer and nut, otherwise use the washer as specified for high or low.

The bottom of the cistern is about 40cm above the connecting pipe so I'm going to assume it's a low level cistern (rather than being mounted above head height, for example).

It's definitely not close coupled.

[GasEngineer]

Chicken_Satay said:

The bottom of the cistern is about 40cm above the connecting pipe so I'm going to assume it's a low level cistern (rather than being mounted above head height, for example).

It's definitely not close coupled.

In that case use the low level washer . The high level one looks to be for a smaller diameter flush pipe.

[Chicken_Satay]

GasEngineer said:

In that case use the low level washer . The high level one looks to be for a smaller diameter flush pipe.

Yes, you're right. I tried the high level washer and it was very tight. I fitted the low level rubber washer for what I have assumed is a low level cistern and it seems to be holding up fine so far.

The instructions also don't make it completely clear where the spill over point is for the internal overflow but I found that out by emailing the manufacturer today.