Bends in Waste pipe

[mps1mps1]

G'Day All,
After a crawl under the house to find fuel for our next council cleanup I noticed 3 x 90 Deg. bends in the bathroom toilet waste pipe.Nothing else connects to this pipe until it branches into our second toilet waste pipe via a Y junction. No vent pipe found. As yet we have never had a problem but I'm sure I've read 90 deg bends should never be used for sewer pipes.
I (novice)have searched your fantastic forum site but failed to find Info.
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mps1mps1

[davo2310]

it doesnt need a vent if it runs less than 8.5metres from the main line, or less than 3 wc's.
90 bends can be used, I prefer to use 2 x 45's, as long as there is a good fall. It should have an inspection opening at or close to the first bend also.

[mps1mps1]

Thanks Davo,
I'll sleep better tonite.