How Much Water Does a Toilet Tank Hold

There are standards for how much water should be used when a toilet flushes. In the past toilet designs needed far more water to flush, but nowadays toilets use much less. Today, I will explain how much water a toilet tank holds.

On average, a toilet tank holds 1.28 gallons (4.9 liters). The regulated water a toilet tank can hold in the USA is 1.6 gallons (6 liters). When the handle is pressed it lifts a flap called a flapper. The flapper stays lifted on most toilets until virtually all of the water in the tank is emptied.

A toilet accounts for almost 30% of the water used in a home. Below, I will explain how much water a toilet uses per person and if it’s possible to pour water into the toilet tank.

How Much Water a Toilet Uses

A toilet has a very simple design that uses the vacuum created by water to empty the bowl. Water consumption in some regions needs to be carefully considered, especially in a drought. So, here’s how much water a toilet uses.

Toilet Water when flushed

Overall, a toilet uses 0.42 gallons (1.59 liters) to 3.84 gallons (14.5 liters) per person per day. The large range is due to the fact that there is a lot of variability in how often people go to the toilet. An average person uses the toilet 3 times a day to 3 times a week.

The amount of water a toilet uses per flush should be under 1.6 gallons (6 liters), according to the US EPA.

Based on these numbers below is a table that shows the range of how many poops a person does on average per week. And below that is how much water this uses. I have used an average of 2 pees per day. However, this can vary as many people drink a lot of water, and pee a few more times. Or, they will only use a half flush, if a toilet has one.

Times the toilet is usedHow it’s used
173 poops a week, 2 pees per day
207 poops a week, 2 pees per day
282 poops a day, 2 pees per day
353 poops per day, 2 pees per day
Number of times the toilet is used per week per personAmount of water used
1722 gallons (83 liters)
2026 gallons (118 liters)
2836 gallons (164 liters)
3545 gallons (205 liters)

These numbers can be adjusted based on how many people are living in a house. For example, if two people live in a house the numbers will double, and for 3 people, the number will triple.

How this water gets used in a toilet

The way a toilet works is largely a mystery unless you’re a DIY person or a plumber. Everyone’s large aware that water somehow washes away what’s in the toilet. But, knowing how it flushes exactly can help a lot if there’s an issue with your toilet.

top view of toilet with toilet tank open

The way a toilet works is very simple. The tank at the rear of the toilet is full of water. The bowl of the toilet has a kink in the pipe. The force of the water that enters the bowl pushes the water and waste up. It then begins to travel down. As it does the water flowing down after the kink creates suction. This suction pulls the remaining water and waste down.

This is why you often hear a gurgling type sound as the suction runs out of water and waste to suck. The tank is also very interesting. It has a rubber plug that sits above a large hole. When you press the handle it lifts the plug, and the water flows through. Most toilets have a plug design that causes the plug to slowly go down until it’s completely covering the hole again.

On some toilets though, you need to hold the plug for about 2.5 seconds, to give enough time for all the water in the tank to flow into the bowl. Here’s a really good video from a plumber that shows how a toilet works in cross-section:

In the video, he also explains what causes common issues with toilets.

Should a Toilet Tank Empty Completely When Flushed?

A toilet has an interesting and well-thought-out design that works very well. The water tank has a lid so it’s impossible to see if the water tank empties completely unless you take the lid off and watch. However, is the water tank on a toilet supposed to empty completely when you flush it?

Generally, a toilet tank should empty completely when it’s flushed. But, it’s common for the tank to have about an inch (2.5 cm) of water accumulate at the bottom of the tank as it’s flushing.

As you flush a toilet, water will begin filling the tank. By the time the flush is finished, there will be about 1 inch of water already sitting in the bottom of the tank. It will then continue filling automatically until it’s full. This is controlled by the buoy type mechanism that floats up as the water level rises, and shuts off the water inlet valve.

pouring water into a toilet tank
Image from 03Recipes

Can I Pour Water into a Toilet Tank?

If the water tank in a toilet is not working properly, it can be a good idea to fill it manually. So, here’s whether it’s OK to pour water into a toilet tank.

As a general rule, it’s perfectly fine to pour water into a toilet tank. A toilet water tank holds approximately 1.28 gallons (4.9 liters). The water tank in a toilet typically will have an overflow pipe. When the water level gets too high it will drain into the bowl.

Therefore, you don’t necessarily need to worry about overfilling it. In general, you should fill it up completely. A toilet is designed to flush the best, and not clog if the entire water tank empties into the bowl.

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