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Disappearing Toilet Water

The Natural Handyman

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Dear NH,
I notice that my second floor guest bathroom toilet bowl will become empty after sitting unused. I also have a water spot on the ceiling directly below the bathroom. There is no evidence of water on the floor in the bathroom, though. Can the water in the bowl water leak around the seal under the toilet without showing on the bathroom floor?
EN from Loveland, OH

Leakage around the toilet flange seal, or "wax ring", and the water draining from your bowl have no obvious connection to each other. The water in the bowl cannot escape any more easily than water in a coffee mug (unless you're a klutz and knock it over). This leads me to believe your toilet bowl may have a small crack in it.

Since you have evidence of a leak via the water spot on the ceiling below, I would take action immediately. This would consist of draining the toilet of all water, disconnecting it from the supply line, unbolting it from the floor flange and turning it over for a "look-see". It should be fairly obvious if the toilet has a crack because water leaks generally leave telltale signs such as discoloration or mineral deposits.

You might also like: Renewing Bathroom Sinks

The wax ring can also develop a leak but that would not account for the water disappearing from the bowl. The only water that passes by the wax ring is the water leaving during a flush. The water that remains in the bowl is there precisely because it is below the level of the toilet's built-in trap. Of course, you could have both problems. Removing the toilet will allow you to diagnose both.

You could also have a leak in the drain pipe, but I would err on the conservative side and leave that issue out of the repair equation... for now. Once you are sure that toilet is not broken (or you get a replacement) AND a new wax ring is properly installed, you should then be concerned if the water stain on the ceiling becomes larger. Before repainting the ceiling, give it at least a few weeks to thoroughly dry out.

If the leak still exists, the next step would require cutting open the ceiling beneath the toilet... not a conservative effort to say the least but in some cases necessary!

Related: First Aid for the Bathroom

Can a toilet leak with no obvious evidence? The answer is an unqualified yes! Fact is, most slow toilet leaks are NOT detectable because they develop slowly. This has to do with the design of a toilet drain. The drain flange, the top part of the toilet drain to which the toilet is attached, comes through a hole in the floor. Most small leaks will not appear around the base of the toilet but instead either travel down the drain pipe OR creep under the flooring material since the flange is at the same level or slightly beneath the level of the finished floor. This is true regardless of the flooring material... tile, vinyl sheet, vinyl tile or one of the newer plastic laminate floorings.

This stealth-type of leak is the most damaging because it can go undetected for many months or even years until the ceiling below becomes stained and moldy or, worst case, the plywood subfloor under the toilet begins to weaken, rot or warp. Vinyl flooring can cause the worst subfloor rot because it is nonporous; the trapped water cannot easily evaporate. Tile is a close second since it is also nonporous. Unfortunately, a wobbly toilet is often the first symptom of serious deterioration in the floor.

About 5 years ago, a client needed a toilet removed for a vinyl flooring installation. When I lifted the toilet, the floor underneath was soaking wet, the dampness extended for a few feet on every side of the toilet under the old vinyl flooring. The wood was thoroughly soaked and quite rotten in spots.

As if that wasn't bad enough, within minutes the room was flooded with carpenter ants! They had detected the soft, rotten subfloor and made a substantial nest... right between the layers of plywood! All in all, a four-foot square section of floor had to be replaced before the new flooring could be installed. The customer afterwards commented that they had an ant problem for years, but spraying never seemed to help... now we know why! Who would have thought that the ants were nesting under a second floor toilet!

Have a small home repair question for THE NATURAL HANDYMAN? Just click here NaturalHandyman.com/aitikia. For more home repair information, visit NH's growing list of original home repair articles and quality links NaturalHandyman.com. If this information has been valuable to you, please consider making a small donation to support NH's free service to the home repair community! For more information, please visit our "Friends" page NaturalHandyman.com/Friends.

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