Toilet bowl empty after flush

[Stotty1]

Do you know anyone, with a drone, fitted with a decent camera?

Not a bad shout, I will ask around at work

 

[Stotty1]

Sounds like a 1/2 blockage & you really need that manhole cover off. It will give you the opportunity to rod both ways up or down the soil pipe.

Agree I need to finally get the manhole cover moving, that is certainly on my to-do list this weekend.
I'm just hoping I can find a way to ease it free and not have to rip it out and replace it

 

[HERTS P&D]

Just call out a drainage engineer/giving you a fixed quote to lift the manhole and jet the drainline and stack if needed

Andy

 

[Dereekoo]

Sounds like a 1/2 blockage & you really need that manhole cover off. It will give you the opportunity to rod both ways up or down the soil pipe.

Partial blockage may lead to gurgling but not to suction of toilet u bend

 

[HERTS P&D]

Partial blockage may lead to gurgling but not to suction of toilet u bend

Oh yes it does.

Andy

 

[Dereekoo]

Is it Christmas? Oh no it doesn't - but I am quite happy to be enlightened how the law of physics works on this hypotheses

 

[HERTS P&D]

I didn't know that you are a drainage engineer Dereekoo.

Andy

 

[Dereekoo]

I didn't know that you are a drainage engineer Dereekoo.

Andy

Well not a drainage engineer as such but spent working life designing sewage treatment works getting flow from inlet to river discharge through various sized gravity/pumping mains along with all the necessary supporting infrastructure, with a bit of mains drainage and potable water works thrown in along the way. Probably why I try and analyse things based on hydraulic/ mathematical principles but keep an open mind on how others see things and if need be learn from their experience."Every day is a school day"

 

[HERTS P&D]

Well, clearing manholes on a daily basis, when a customer calls me and tells me that all the water in their toilet has gone, I ask them to lift the nearest manhole and every tme they tell me that it is full.

As you say, 'every day is a school day'.

Andy

 

[Harry Bloomfield]

Well, clearing manholes on a daily basis, when a customer calls me and tells me that all the water in their toilet has gone, I ask them to lift the nearest manhole and every tme they tell me that it is full.

I believe you were being asked to explain the mechanism, that would draw the bowl water out, from the bowl, due to a downstream blockage - assuming the vent was working???

 

[robinbanks]

Birds nest in the end of the soil vent pipe?

 

[Hugh Jaleak]

I believe you were being asked to explain the mechanism, that would draw the bowl water out, from the bowl, due to a downstream blockage - assuming the vent was working???

I'm still trying to work out the logic, but I have an issue with my upstairs WC on occasions, (too much paper and it'll block solid), which requires a suitable prod with a plunger to shift. When the blockage goes, and the pan empties, it does cause some gurgling in the adjacent shower, which is connected into the stack at a suitable point below the WC junction. The stack is vented.

My first thought was slight suction, as the plug of waste and water fills the stack and pulls the air behind it, but then the stack is open to atmosphere, top is clear, so no reason why it shouldn't allow free passage of air behind the water.

Funny old things, drains.

 

[Harry Bloomfield]

My first thought was slight suction, as the plug of waste and water fills the stack and pulls the air behind it, but then the stack is open to atmosphere, top is clear, so no reason why it shouldn't allow free passage of air behind the water.

How about - shower entering below the toilet entry, two plugs of material, gap between and the two plugs acting like pistons. The first one will accelerate quicker than the one above it, forming a slight vacuum, between them. The gurgle, being the vacuuming of the shower trap?

 

[Dereekoo]

I believe you were being asked to explain the mechanism, that would draw the bowl water out, from the bowl, due to a downstream blockage - assuming the vent was working?

How about - shower entering below the toilet entry, two plugs of material, gap between and the two plugs acting like pistons. The first one will accelerate quicker than the one above it, forming a slight vacuum, between them. The gurgle, being the vacuuming of the shower trap?

Or during normal operation of the bowel a plug of water is projected into the soil pipe in a semi controlled way depending on how fast the cistern discharges with lots of air injected into it at the same time which prevents a suction of sufficient magnitude developing in the soil pipe enough to cause any issues with the shower trap, suddenly plunging a large solid mass of water/debris down the soil pipe creates a suction (or air pressure wave) just large enough to have an effect on the shower trap. I should imagine the difference between the parameters affecting the shower trap are quite small a bit like blowing down a straw into your coke and causing bubbles. We need some input from an experienced drainage engineer ( aka plumber)

 

[robinbanks]

For example

For the entire time a plug of waste is in the red section it will create a low pressure which will stabilise by some air/water being drawn in at the shower trap and the toilet (which is a trap shape)
When the plug reaches the stack, it will have an easier time drawing air down the stack rather than through the traps to equalise pressure

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)