Kitchen gully

[G&M]

Can somebody confirm what is the correct way to install a new kitchen gully as I've seen the following three variations :

First is a 40mm pipe out of the kitchen wall discharging above a hopper and gully grid such as

is the same but with the discharge pipe extending through a hole cut in the grid.

Third is directly into the back of a back inlet grid, possibly such as

I don't see how this one provides a U bend.

Many thanks

[Set Square]

AIUI, your first option is unacceptable - and you have to take the waste pipe below gulley grid level - so option 2 is ok. Option 3 (bottle gulley) has U bend inside it - achieved by means of internal baffles - and should be ok.

I assume that you are talking about the U bend prior to the sewer connection point. This is, of course, separate from and additional to the trap or U bend *inside* the house, immediately under the sink.

[G&M]

Thanks. What would a new build most likely use nowadays ?

Yes. The deeper type of bottle traps under every plug hole.

[Set Square]

Probably your option 2. I think it's cheaper! Bottle traps have their outlets much nearer to the surface. This is often a pain - but can be useful if you haven't got much fall into the sewer.

[G&M]

Thanks - option 2 is cheaper, hence I assumed probably not preferred by BCOs ! :-)

Plenty of fall into septic tank - friendly farmer with digger saw to that before doing the pond.

[Set Square]

I think option 2 will be preferred by builders - and will be perfectly acceptable to BCOs. As well as being cheaper, it provides a lot more flexibility when installing and aligning the pipework.