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 Toilet Water Gets Gone
Author: Plugdup (CA)

This has been going on for 35 years. Sure I’ve lived with it but would like to solve it.

Got 2 toilets not back to back - maybe 20’ apart on a straight line. Both vented to a common vent system; there is ony one pipe through the roof. One of them looses water such that the internal trap gets emptied or at least partially emptied. This does not happen all the time. Just some times and the rate of loss varies. Only the one toilet and not the other; never the other.

First reaction will be that it leaks; but! When away for vacation I would remove the toilet from the pipe, stand it in the shower, cover the bowl with plastic wrap so the water could not evaporate and after 2 weeks the water had not drained. Not a fraction.

My only thought is that the wind over the vent pipe opening creates low pressure thereby sucking the water out of that toilet. But why not both toilets? And if that is so why would it continue to suck water out after the trap is partly emptied? Probably wouldn’t. I suppose it might suck out just enough that the trap is ineffective but still has some water in it. Not only that it happens with or w/o wind.

Sewer fumes have gotten into the house but maybe less than would be if the trap was fully emptied. The fumes have been smelled for sure.

I cannot relate this to wind or heat or cold or temperature or weather or time of year.

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 Re: Toilet Water Gets Gone
Author: stuckinlodi (MO)

The toilet that loses water, is it just evaporating because it is seldom used? Is it one of those toilets that doesn't have a lot of water in the bowl even after it is flushed and refills?

If you stand by this toilet that loses water and watch it while someone flushes the other toilet do you see the water in the bowl surge up or down as if pressure in the line is affecting it?

Sewer fumes coming in indicates a trap is getting empty or air pressure in the sewer line is burping thru. If it is affecting the toilet trap in that bathroom then it may also affect the smaller traps in the tub or sink in that room. Also, drains that go unused for awhile can have their traps lose water just from evaporation.



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 Re: Toilet Water Gets Gone
Author: Plugdup (CA)

Hi-
Not evaporating as it is used regularly. The level drops too fast for evaporation.
As I type the water is down about 1/2 inch since about 3 hours ago.The water level is where it’s supposed to be right after the flush and fill. Right at 3 inches below the edge. I just now measured to the water mark.

There are 2 other traps; sink and shower - I’ll try to figure a way to check those levels. All used regularly.
I will try to watch while the other toilet is flushed but this one will empty out by itself when we are away and neither is being used.

I did not swap the toilets. Not impossible, of course, but what a pain.

On vacation for 2-4 weeks with the toilet removed and pipe plugged there would be no fumes which would say the other traps did not dry out. Or at least not enough to allow fumes. No problems elsewhere in the house. No plumbing problems that is. :-)

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 Re: Toilet Water Gets Gone
Author: stuckinlodi (MO)

You've done a lot of investigating, everything you've said seems to point to that individual toilet fixture or its vent. Since the toilet bowl will hold water for the 2 weeks you are gone on vacation if it is pulled from the flange and is sitting in your tub then the toilet seems ok, no hairline crack that is leaking water out of the bowl.

I agree, if you are not getting sewer smell when you pull that toilet and cover it with airtight cover then the other drains in that room are ok. What about flushing the other toilet while watching this toilet's water level, see if it surges? If it does that would point to a venting problem I think. Have you inspected its vent pipes (in the attic?)? How difficult would it be to put the bad toilet on its own vent, even temporarily to see if that fixes it?



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 Re: Toilet Water Gets Gone
Author: Plugdup (CA)

I just did the flush test - flushed one then moved with alacrity to the other probably 2-3 seconds - did not see a perceptible movement of the water. Presumably a surge would be a significant movement that would take at least a short time to settle out?

The vent pipes for the various units are inside the walls and near as I can tell are manifolded into the bigger vertical rise thence thru the roof. A separate vent tho a good test would be a horrific job. I think. I’m not a plumber, don’t know all you guy’ s tricks. Unless it could be done in the crawl space. The pipe is ABS.

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 Re: Toilet Water Gets Gone
Author: stuckinlodi (MO)

Is the toilet that loses its water the one closest to where your house sewer line runs out from under your house and goes to connect to the street? Is it the last fixture on your home sewer line, so it is closest to the street? Wondering if something out there is pulling enough to put a negative pressure on the drain line and the first trap in your home gets sucked out. But really, this is a stumper, and you've been thinking about it off & on for 35 years.

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 Re: Toilet Water Gets Gone
Author: Plugdup (CA)

It could very well be the last. I’ll check that out ASAP but it’s raining now - I’ll wait a couple days or at least till it lets up for a while. Steady rain predicted for several days.

I’d like to put a new low flow unit in but not w/o solving this. I wonder it I shouldn’t try to find another older model like mine and install that - see what happens. They should be cheap or even free. Probably take 5 years to confirm anything. Jeez.

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 Re: Toilet Water Gets Gone
Author: stuckinlodi (MO)

You could try another toilet but honestly I'm not so sure the toilet is the problem. You've proven that the toilet holds water in the bowl for weeks if it is pulled from the floor and sits in the tub with the bowl covered, water level does not drop. It sounds like you have an unusual situation, that's why I got to thinking maybe some external force is sucking on the air in the line on your house sewer sometimes, enough to pull water from this toilet trap if it was the closest trap to the outside world. But if that was the cause you'd think the tub and sink drains in that bathroom would also lose water - but maybe they are losing water since you can't see them like you can the toilet bowl water level.

It seems like you are interested in getting to the bottom of this, so by either swapping the two toilet fixtures you have, or getting a third one and installing it in place of the one that loses water would give you more information about the problem. It's as if there is something else we aren't considering or know about that would explain what is happening.

If you are leaving the seat up all the time maybe your thirsty dog is drinking all that water from the bowl?

EDIT- another idea, climb on the roof and add some kind of a gooseneck attachment to the vent pipe for that bathroom, that will reduce the effect of any wind blowing across the vent. Maybe put a wadded up piece of screen wire inside the end of the gooseneck that points downward. They make screen covers for the vents to keep small animals out, that might work also. The idea is to let air move in the vent but reduce the large opening to something subdued to the effect from wind. If the wind is causing the problem I don't know why it only affects one of the toilets. Longshot, but easy to do.



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 Re: Toilet Water Gets Gone
Author: Plugdup (CA)

I just Googled >sewer sucks water out of trap< and there must be a million others with a similar problem. Lotsa answers. Mostly venting related suggestions. Only difference from my situation is that mine will empty out constantly for a period of months then not do it for up to several years.

I’ll crawl under when it quits raining see what I can see. I have all the drawings for the house - maybe there is a piping plan - might provide a clew. Might, that’s a long shot. I designed the house but an arkytekt drew the formal plans and I’ve always thought they weren’t exactly detailed like an engineering drawing - just the general idea. Well it’s just a house not a machine.

Anyway thanx for trying to help and if it gets solved I will let you know unless I lose the link to here or cash in. I’m getting damn all old. If I have to sell out I’d sure like have it solved for the new owner.

How about this? Set up a small pipe system like an ice maker in a refer with a timer that would shoot a cup or 2 of water into the toilet bowl. If by chance the bowl got too full it would just flush itself. It would be easy to tap into the water supply with a 1/4” tube. A float valve in the toilet bowl would work too but might be a tad bit inconvenient. Have to mount it on a pivot of some sort to move it aside at certain times.

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 Re: Toilet Water Gets Gone
Author: North Carolina Plumber (NC)

They are called a trap primer. It might work but it's only masking the problem, not correcting it.

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 Re: Toilet Water Gets Gone
Author: Plugdup (CA)

Thanx for info. I will look into that trap primer. I see there are several concepts.

Actually I was joking. Never thought there might such a thing. Sure shows the difference between a DIYer and the PRO’s.

Another idea I had was to set up an IV drip set on top of the tank.

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 Re: Toilet Water Gets Gone
Author: stuckinlodi (MO)

Your situation might be the only time a leaky flapper valve would be helpful. <ha - not a good idea, wasted water>

Do you have a sewer line cleanout access in your yard somewhere, like for roto-rooter to cleanout the line? If so, what about removing the cap on the cleanout, then sit it loosely over the cleanout hole or remove it altogether. Leave it this way for a few days, see if the bad toilet no longer loses water. If something out in the sewer system is exerting negative pressure on the line and sucking your toilet trap water then doing this will let outside air into the line and not pull on your toilet trap. Just something to try. Might want to put a box or something over the cleanout to keep stuff from getting into the sewer line while the cap is removed or loosely sitting there.



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 Re: Toilet Water Gets Gone
Author: Plugdup (CA)

I’ll try that too. Actually I had thought of something like that except sealing a thin diaphragm over the clean out and see if it bulged in. It’ll have to wait for now as it rains every day like a cow on flat rock. What a drag.

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