Advice please - toilet water level varies

[ljcox]

Our house is about 10 YO and we have always had a problem with the second toilet (toilet 2 in the drawing attached).

Once or twice every few weeks, I find that the water level in toilet 2 has gone down and on occasions, it has gone down so far that sewer smell comes up. We rarely use this toilet.

I think it may have happened with toilet 1 on the odd occasion also.

My understanding is that the air relief pipe should be at the end of the run, ie. where the pipe leaves the house.

But our's is between the 2 toilets.

Do I need to employ a plumber to instal another air relief pipe? If so, where?

The drawing is not to scale.

[wonderplumb]

Nothing wrong with vent position, however there is no pipe lengths or pipe sizes so its a little hard to tell. Could be the proximity of a branch drain to the junction for the toilet, the toilet looks to be a junction on its back on the main line. Could be a partial blockage somewhere.

[Ron Dunn]

Your cheapest, most efficient solution is to flush the toilet once a week, used or not.

The water is probably evaporating, or possibly escaping through a slow leak somewhere. If evaporation, there is nothing you can do about it. If a leak, and if it is so slow that you're only losing a cup or two per month, then it isn't worth pursuing.

Just flush occasionally.

[wonderplumb]

I doubt that much water would evaporate in a few weeks, nor would the toilet be leaking to lose the water, it would be all over the floor!

[DavidG]

Air pressure in the house causes it.

Have the same happen here and I tracked it down to having a door open that is facing into the wind and no other windows or doors open.

The wind increases the air pressure and pushes the water down in the bowl causing some to escape.

Stronger the wind, bigger the effect.

ps: yes I stood and watched it happen...... Gee I have a lot to do....

[Ron Dunn]

wonderplumb, I'm guessing you are a plumber, so you definitely know a lot more than me. I definitely won't debate with an expert

That said, I've had a situation like this before. Both downstairs toilets used to go dry if you were away from the house for more than 2-3 weeks. I've heard of similar problems from estate agents trying to sell empty houses ... unless someone flushes the toilets occasionally, there is a chance the bend will dry out.

Can't be sure of the cause, but the remedy I've always heard is to flush the toilet occasionally.

[wonderplumb]

Of course they do dry out, as does the floor waste and sink traps etc, but I think its more sinister than that. With the air pressure thing its more in the vent pipe itself than in the house, a wind blowing across the vent pipe, which can be affected by the proximity of a pitched roof will cause pressure fluctuations and if not vented correctly will cause a fixture to suck its seal. Mostly found in boundary trap areas though.

[bricks]

A couple of questions?

Does the loss in water seal happen around the same time as the laundry is used?

Do you ever hear gurguling sounds from that toilet?

Does the toilet flush ok or does the water rise up alittle in the pan first.?

PS over here in S.A. the vent needs to go between the last two fixtures so therefore yours would be on the wrong side of the ensuite run.
Im reasonably sure that this is the rule for all of australia?

[wonderplumb]

Not quite, they say the last two fixtures only because you require at least one fixture running past the vent so the vent doesnt block in the event of a choke. The rule is you cant have any more tham 10m of unvented drain, so as long as those fixtures are within 10m of the vent they are OK, however the LT point and the BSN drain seem a bit suss.

[ljcox]

Nothing wrong with vent position, however there is no pipe lengths or pipe sizes so its a little hard to tell. Could be the proximity of a branch drain to the junction for the toilet, the toilet looks to be a junction on its back on the main line Yes, the toilet pipes are perpendicular and go straight into the main. Could be a partial blockage somewhere.

Thanks for the prompt responses.

I have used a plan of the house to estimate the pipe lengths and have added the pipe diameters.

I don't think it is due to evaporation or when the laundry tub is drained, it seems to happen at random. But I'll keep these possibilities in mind.

I assume it is not a partial blockage as (as far as I can remember) it has been happening since the house was built 10 years ago.

A couple of questions?

Does the loss in water seal happen around the same time as the laundry is used? No, seems to be at random

Do you ever hear gurguling sounds from that toilet? No

Does the toilet flush ok or does the water rise up alittle in the pan first.? It flushes normally

PS over here in S.A. the vent needs to go between the last two fixtures so therefore yours would be on the wrong side of the ensuite run.
Im reasonably sure that this is the rule for all of australia?

Thanks for the response, answers above.

Of course they do dry out, as does the floor waste and sink traps etc, but I think its more sinister than that. With the air pressure thing its more in the vent pipe itself than in the house, a wind blowing across the vent pipe, which can be affected by the proximity of a pitched roof See below will cause pressure fluctuations and if not vented correctly will cause a fixture to suck its seal. Mostly found in boundary trap areas though.

The roof has a 30 degree pitch and the vent pipe is about 200 mm long after coming through the tiles.

[wonderplumb]

Every thing seems OK except for, the hand basin line to toilet 1 is a bit far for 40mm and reduced too close to the toilet, shower to toilet 1 seems to take off too close to the toilet point, the bathroom group on the downstream side of toilet 2 is sized incorrectly, it should be atleast 65mm from where it picks up the bath. This is based on the info you've given me though, assuming the sizing and measurements are correct, as far as venting goes there is nothing wrong with the way its installed. Is there a possibility the vent may be blocked? Birds nest or something? The cowl hasnt been broken in a storm allowing birds in there? Just a few more possibilities. Do you know if your in a boundary trap area or not?
Though not really relevant where is your floor waste's and your surcharge gully?

[ljcox]

Every thing seems OK except for, the hand basin line to toilet 1 is a bit far for 40mm and reduced too close to the toilet, shower to toilet 1 seems to take off too close to the toilet point, the bathroom group on the downstream side of toilet 2 is sized incorrectly, it should be atleast 65mm from where it picks up the bath. I'll go under the house and check on these points. It was done by a brief visual inspection & looking at the house plan. I assumed that the 50 mm pipes are 50, they may be 65. I'll check. This is based on the info you've given me though, assuming the sizing and measurements are correct, as far as venting goes there is nothing wrong with the way its installed. Is there a possibility the vent may be blocked? I'll push a hose down it to check. Birds nest or something? The cowl hasnt been broken in a storm allowing birds in there? No the cowl is OK. Just a few more possibilities. Do you know if your in a boundary trap area or not? I don't know what a boundary trap area is.
Though not really relevant where is your floor waste's and your surcharge gully?

Thanks for the response. I don't know what you mean by "floor waste's and your surcharge gully".

[wonderplumb]

A boundary trap is your shaft at the boundary before the drain enters the sewer main. If it is a boundary trap it will basically be an 'S' bend at the bottom that holds water, accompanied by a tin looking vent next to it somewhere. If not it will be a straight shaft with no water in it and no vent. A floor waste is the floor drain in your bathroom, which can be connected to the sewer with a fixture running through it or dry, which will discharge outside the house with a flap over the end of it, most commonly 2". A surcharge gully is outside the house, usually at a low point, with a grate over it and holds water also. Usually about 3" above ground level and may or may not have a garden tap over it. This is what over flows when the sewer blocks up and stops the sewage coming up through your floor waste or your shower.

[ljcox]

A boundary trap is your shaft at the boundary before the drain enters the sewer main. If it is a boundary trap it will basically be an 'S' bend at the bottom that holds water, accompanied by a tin looking vent next to it somewhere. If not it will be a straight shaft with no water in it and no vent. A floor waste is the floor drain in your bathroom, which can be connected to the sewer with a fixture running through it or dry, which will discharge outside the house with a flap over the end of it, most commonly 2". A surcharge gully is outside the house, usually at a low point, with a grate over it and holds water also. Usually about 3" above ground level and may or may not have a garden tap over it. This is what over flows when the sewer blocks up and stops the sewage coming up through your floor waste or your shower.

Thanks. No we don't have either a boundary trap, a floor waste drain or a surcharge gully.

I went under the floor and made some measurements. I also discovered that some of my assumptions were wrong. See the attachment.

The 50 mm pipes are definitely 50 mm, not 65.

[bricks]

Hey bloke been doing alittle research on your predicament.

Wonderplum hasn't told you anything I think is incorrect.

But I don't agree as a plumber with the position of that vent- I just doesn't look right to me.

For Wonderplumb I really think that the vent should go on the upstream side of the ensuite run.
This is due to Clause 3.9 (c) in your code book. Reffering to the upstream end of the drain, this drain drawing to me looks like its in the middle.

Although I'll say it now that this drain doesn't technically break any rules!

Would you agree that a good solution as far as cost might be concerned would be to cut in an AAV at the kitchen sink under the bench?

This would do two things

• There would then be a vent in an upstream position of the drain, removing the position of the vent as a possible cause.
• It would add and extra vent which wouldn't hurt as the fixture unit rating is quite high for a 50mm vent. ( still legal though)

Cost about $75 If done at home by handy man?

You also should check the falls on your drain, a 10mm spacer on the end of a 600mm level will give you the correct fall.


My hypothetical reaoning behind the problem is that the water from the kitchen sink, laundry trough and bath may be stalled at the last bend before exiting the building. This might be causing the pipe to fill up at this point, creating a suction every time a large flush occurs.

It's the only thing I can think of other than tree roots or an undergrade drain, Both of these are readily obvious seeing as the drain is visible.


See what wonder plumb says but for the cost associated with doing it, I think that you'd be foolish not to try adding an extra vent ( AAV) under the sink.