Why Does Wind Drop My Toilet Water Level?

If you’ve ever been in your home’s bathroom on a windy day, you may have noticed a strange phenomenon: water in the toilet bowl appears lower than normal. If you have noticed a lower-than-normal toilet bowl water level, what you may not know is that there is a scientific principle that explains the scenario: Bernoulli’s principle.

A scientific explanation
Bernoulli's principle applies to the concept of fluid dynamics, and states that an inviscid flow – one without resistance or interference – can only be produced when an increase in the speed of the fluid occurs at the exact same time as a decrease in pressure or a decrease in the potential energy of the fluid. Any imbalance between these two properties results in interference in the substance's fluidity.

Most homes in the United States feature plumbing systems that include a vertical pipe known as a vent stack. This pipe extends upwards from the downward-leading drainage pipe and out through a home’s roof, with the uppermost opening of the vent stack exposed to the outside elements.

Why vent stacks matter
The vent stack is designed to release sewage gases outside to help prevent toxic gases and unpleasant odors from entering the home. In addition to expelling these gases, the vent stack also moves air from outside through the pipes, which ensures smoother and more effective draining of wastewater and reduced gurgling effects.

When applying Bernoulli's principle to the phenomenon of decreased water levels, it's understood that fast winds blowing through the vent stack results in decreased air pressure within the drainage pipe.

Less pressure means lower water levels
Because fluids like air and water tend to move towards area of decreased pressure, lower air pressure results in a suctioning effect throughout the plumbing system, which ultimately lowers the water level in your toilet bowl. Alternatively, calmer weather conditions result in increased air pressure in the toilet and higher water levels as a result.

Understanding the role of vent stacks in your plumbing system may help you identify plumbing complications in the future. Although vent stacks usually require very minimal maintenance, you should make sure to contact a professional and licensed plumber to correct any problems that you believe may be related to your home's vent stack.

A professional would understand the appropriate approach to take, in addition to having the tools and experience necessary to repair the problem in the most effective manner possible.

If you feel your home’s vent stack needs repairs or improvements, don’t hesitate to call on a qualified and licensed plumber. Whether you’re seeking a Boston plumber or a Chicago plumber - or a plumber in any other city in the country - you can find verified reviews written by local consumers and homeowners like you on Angie’s List.