Toilet Water Level Recedes After Flushing? [Here's Why & Fixes]

Most people flush their toilets all the time, and rarely give it a second thought. In fact the average American flushes a toilet 5 times a day, usually without concern. If you notice once you flush, the water in your toilet bowl slowly begins to recede, however, you may start to flush your toilet with more concern.

If the water in your toilet bowl is receding there is a problem with one of the pieces in your toilet. The water level is controlled by the intake valve, flapper valve and float valve, so be sure to test these components immediately. Also check to make sure seals work properly and the toilet itself is not cracked or damaged.

Finding the cause of the water level receding in your toilet after a flush requires a bit of detective work. The most obvious place to look is at the toilet itself.

Water leaking by the flapper valve can sometimes cause the toilet bowl’s water level to recede slightly. The flapper valve must seal tightly to the valve ring on the bottom of the tank. If the flapper valve is damaged, it may not seal properly.

Inspect the outer edge of the flapper valve for wear, tears, or cracks. Some flapper valves may get so soft with age and use that they won’t make a seal. If you suspect that the flapper valve is leaking, replace the flapper. Flapper valves are available at almost any hardware or home improvement store.

If the water level in your tank is too high or too low, the tank flush valve may not operate properly. When the flush valve doesn’t operate correctly, the toilet bowl’s water level can recede or not flush properly.

Most toilet tanks have a mark inside the toilet tank that shows the recommended water level. You can adjust the float valve in the water tank to bring the water level to this mark. The adjustment may be a screw on the float valve, or, on older systems, you must bend the float’s arm.

Your toilet has several seals and gaskets. Two-piece toilets have a gasket between the tank and the bowl. Over time, this gasket may dry out, shrink, and crack. A damaged seal can allow the toilet to leak. This sort of leak is usually obvious and easy to diagnose. A leak at the seal can cause the tank flush system to not deliver enough water for a proper flush

The toilet has a seal ring at the base where the toilet joins the waste pipe. This seal ring may be wax of a man made product. This seal, or bowl ring, can be damaged if the bolts holding the toilet to the floor are loose. As the toilet rocks even slightly, the bowl ring loses its seal.

Some homeowners may feel comfortable tackling the job of replacing a tank gasket or bowl ring. However, these are often jobs best accomplished by a licensed plumber. In some cities and towns, local building codes mandate that a licensed plumber make these types of repairs.

A crack or other damage to the toilet bowl can allow water to escape from the bowl. You will notice a drop in the water level in the bowl when a leak occurs. Damage to a toilet bowl can occur if objects drop into the bowl or the toilet is subject to undue stress.

Sometimes, a crack or damage is easily visible. Objects falling into the toilet bowl may leave cracks or even holes in the porcelain. However, hairline cracks are often hard to see.

You should never stand on your toilet. Your toilet is not a stepstool and the stresses can cause the toilet to crack or even collapse. Uneven pressure on the toilet’s edges may cause cracks inside the toilet or on the outside at the base. Replace any toilet that has cracks or damage immediately.

A receding water problem may not be in your toilet at all. The receding water level could signal a deeper problem in your waste handling system. In some cases, solving this problem may require the services of a licensed plumber

A clogged or blocked vent pipe can cause the water to recede in your toilet when another drain in your home is in use. The wastewater system in your home must have a clean airflow whenever water is flowing in the drainpipes. To understand this problem, you must understand how the waste system works.

The waste handling system in your home is not just pipes that carry the wastewater to the sewer connection or septic system. The waste piping also has vents that allow air into the waste piping and allow sewer gasses to escape harmlessly outside your home.

When you flush a toilet or turn on the shower, water begins to flow down the drain pipes. AS the water flows downward and outward, it pushes air ahead of the water. If a vent pipe is clogged, there is no air available to replace this air.

The drain system tries to get the air by pulling sucking the water out of any toilet nearby. You will notice that the water level in the toilet bowl recedes.

With a few exceptions, modern toilets use a quite simple method to carry the waste away to the drain system. The process involves gravity, a siphon, and a P-trap built into the toilet.

The water that remains in the bowl after a flush sits in the P-trap of the toilet. This double loop system in the base of the toilet holds the water in the bowl. The water serves as a seal on the waste and drain system to keep sewer gasses from escaping into your home.

Keeping an adequate water level in the P-trap and bowl of your toilet is important for you and your family’s health and safety. Sewer gas not only smells bad, but the gas can also be dangerous if your home concentrations get too high.

When you notice the water in your toilet bowl is receding after you flush, be sure you investigate further. The problem is most likely one of the main components of the toilet like the flapper, the intake valve or one of the seals. The issue may also be a cracked toilet.

Regardless of the source of the problem, you should not ignore the problem. The solution is most likely an easy and cheap fix, and it can save you much bigger headaches down the road. If for some reason you cannot find the source of the problem, you can always call a professional to solve the problem for good.