Shower waste size

I have to install a shower to a newly located bathroom. My question relates to the strange routing the waste discharge has to take due to the customer not being allowed to route the wastes outside due to planning restraints.
I have to route the pipework along the horizontal for 2700mm through a wall and then a drop of 750mm 90 degree bend then 2300 run to tie up with original cast pipework where current bath/shower is situated. where I state horizontal i have plenty of room to ensure the correct fall etc but my question is twofold 1. is 40 mm pipe adequate for this run bearing in mind the vertical drop, 2. will the drop cause an excessive noise and should I increase the diameter here ? or will it be acceptable to slope this section at 135 degrees as it would follow the run down the side of a set of stairs.
I hope this is clear enough cheers for the help.

imo it will be quieter with the 135 degree run rather than the vertical drop. 40mm will be plenty for that length of shower waste. I doubt you would gain anything by increasing the pipe diameter.
I would advise the customer that a little noise from the waste may be inevitable, but smooth flow will eliminate it to some extent. The amount of noise will depend on the routing of the waste(i.e. hidden or exposed and/or insulated), the quality of the pipe itself and how well it is secured, these factors are down to you.

Should all be50mm imo. That's a pretty long run with restrictions at the bends. If water was to run full bore in the pipe it could siphon out the trap and leave bad smells from the stack to get into the new bathroom.

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As kay-jay 50mm and fit a durgo or vent it

I wouldn't have thought a shower would run full bore in 40mm, but I'm outnumbered. 50mm it is then

Thanks people thought that would be required. Its in now and working good.
one more question though , how do you know if someone has replied to your post ? I even have difficulty in finding my own post. any help with this would also be appreciated cheers .

if you are subscribed to the post ( which you automatically are I think, you can go into your profile and adjust things )
you will get an email when someone replies to it.
or if you click on your name then click "view forum posts" it will show the posts you have written.

Cheers Ill try that, Thanks again.

I think the drop will not going to generate excessive noise. You should continue with this diameter, it is pretty much OK.