Toilet bowl empty after flush

[Johntheo5]

Obviously, the first thing on the list is to prove the soil vent clear even if it entails removing the cowl and flushing a good flow of water down through it, migh require a hose brought up on the roof so proceed with caution.

 

[Harry Bloomfield]

It doesn't have to be a full blockage of the pipe; even a narrowing will create a pressure differential, some of which may be resolved by air from the drains filling the vacuum area over the top of the descending plug and other air coming thrugh the traps. There isn't always a huge head of water in a trap; even the pressure change caused by opening the bathroom door can defeat it though that's usually an inwards opening (pressure increase, pushes bathroom air into the drains rather than vice versa)

I thought nothing was allowed to be connected to the soil stack, unless it was connected to the vented vertical stack. In other words, you are not allowed to combine anything with the part which is unique to the toilet?

 

[Dereekoo]

I thought nothing was allowed to be connected to the soil stack, unless it was connected to the vented vertical stack. In other words, you are not allowed to combine anything with the part which is unique to the toilet?

What like this?

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[Harry Bloomfield]

What like this?

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Obviously, you are allowed. I wouldn't do that, it is a great way to suck the water out of the shower/bath/wash basin trap out.

 

[robinbanks]

I thought nothing was allowed to be connected to the soil stack, unless it was connected to the vented vertical stack. In other words, you are not allowed to combine anything with the part which is unique to the toilet?

I predict we'll soon be onto the topic of "what regulation permits vs what people actually do"