Wind blowing across vent pipes on the roof can create air pressure changes within the plumbing system, causing water in traps to bounce. Over time, this oscillation can lead to water loss.
An acceptable solution is add one teaspoon of vegetable oil per inch of drain diameter. This will provide a layer to slow evaporation. Mechanical trap primers are sometimes used as well. Always be sure the condition is not caused by a venting issue or stoppage condition instead of evaporation.
The most likely cause would be syphoning, where the flow of water in the waste pipe empties the P-trap. This could be due to too small a diameter pipe and/or lack of vent in the pipework to prevent a vacuum caused by draining water.
There are two main causes of the toilet losing water from the bowl. 1. Evaporation - it does take time, but water slowly evaporates. Eventually, the bowl will be totally empty (takes about a month or two). 2. Bad vent - toilets have a 3'' drain line, and they are supposed to have a 2'' vent (USA building code).
If the vent stack is blocked and no air can get inside, the pressure from flushing the toilet will often suck all of the water out of the P-trap. Running the sink will fill the trap back up. However, the water will get sucked out of some or all of your P-traps again the next time you flush the toilet.
It is easy to fix a P-trap that ran dry due to a period of inactivity. Flush the unused toilet and pour water down the sink and bathtub drains to restore the P-trap's water barrier. Run water down the infrequently-used bathroom drains regularly to prevent the P-trap from running dry in the future.
Rubber washers might lead to a leak since rubber hardens and dries out over time. If your P trap's washers are hard or deteriorated, or if the washers have become misaligned over time, then they'll need to be replaced or realigned.
Common causes of a low toilet bowl water level include partial clogs, sewer line issues, and problems with the toilet's fill valve or vent pipe, each requiring specific investigative and corrective actions.
Leaks or cracks
The first thing to do is check for any leaks around the base of the toilet, as well as any cracks in the bowl. Either of these two outcomes is likely the cause of the disappearing water.
Have you ever experience the water in your toilet bowl draining by itself or the bowl just can't hold the water? This is a potential sign of a clogged vent inside your walls. Vents are simply pipes connected to all your toilets, tub drains, and sinks and leads to the outside of your home through the roof.
A sewer gas smell in the bathroom can be caused by:
evaporation of water in the P-trap piping. broken seal around the toilet in the wax ring or the caulk. A burst pipe. tree's roots have grown into or have caused damage to your sewer pipes.
One of the simplest reasons a P-trap might dry out is infrequent use of the fixture. In homes where certain bathrooms or sinks are rarely used—such as in guest rooms or basements—the water in the P-trap can eventually evaporate.
Slowly pour about a gallon of water into the drain. This will refill the trap and recreate the seal to block sewer gases. For long-term prevention, consider adding a small amount of mineral oil on top of the water in the P-trap.
Prevent Evaporation
If you frequently travel for long periods, cap the toilet bowl with a toilet evaporation canopy. Canopies cost $10 to $15 and tightly fit the toilet rim. Another solution is to wrap the top of the toilet bowl rim with plastic wrap.
Make sure the top of the P-trap and the bottom of the sink's tailpipe are properly aligned, then tighten the slip-joint nut by hand and then with slip-joint pliers until you feel moderate resistance. Repeat the process where the end of the P-trap meets the drainpipe that disappears into the wall or floor.
Why Does My Toilet Randomly Empty Itself Of Water Without Being Flushed? Most of the time this random occurrence is a result of poor or no venting of the fixture. Vents allow for air flow to the toilet sewage system. Without the vent, air pockets form in the waste branches and can cause what is called back-siphonage.
If the toilet bowl isn't holding water, you may have a crack in the bowl or base. Check for water around the base of the toilet. You'll need to replace the bowl if it's cracked. A clogged plumbing vent is another possibility if the bowl isn't holding water.
Check your water levels
Low water levels in your tank are common causes of toilets filling up with water when flushed. They can also cause slow-draining toilets. You can manually top up your tank with water to help the flush. Then, check the flush tube for cracks and bends that lead to leaks.
If your water level isn't high enough, something is causing it to drop unnecessarily. Often, the explanation is a clogged pipe, a damaged component, or a hidden leak. No matter what it is causing your toilet bowl to empty, you should address the problem as quickly as possible.
Check the water level in the cistern
If the water level is above the overflow pipe, then this will cause the water to constantly overflow into the toilet bowl. This may be caused by a faulty or incorrectly set float.
The flapper, trip lever, or chain may no longer align with the flush valve, leaving a gap which can cause a leak. Over time, grit or sediment can cause small cuts and other damage to the flush valve which can result in a leak between the flush valve and flapper.
Traps can lose their water from too much wind and the air outside of the house, which could be getting into the pipes and may bounce the water out of the bowl.
Is your P-trap working properly? If you detect any foul odors near the P-trap that remind you of a smell similar to rotten eggs, then it means that there is hydrogen sulfide present. This, and other harmful gases, bacteria, and viruses, can get into the house if your plumbing trap has malfunctioned.