How Much Water To Flush A Toilet – Shocking Facts 

Have you ever wondered how much water to flush a toilet used? I am sure many of you think about it. But don’t find it vital or something that needs to be concerned about, right?

Well, now you will be shocked after knowing how important it is to know how much water your toilet uses while flushing and how it affects your water bill. 

How much water should you need to flush a toilet? As an avid plumber, I have always been obsessed with conserving everything, especially water.

This has led me to learn how much water to flush a toilet which I would like to share with you. 

The amount of water used for flushing varies widely depending on your home’s plumbing system and your toilet type. A standard toilet uses 3-5 gallons per flush (GPF), while low-flow models use 1.6 GPF or less.

How To Calculate Your Toilets GDF?

If you want to know what the GDF is for your toilet, you can calculate it by doing this:

Fill the tank with water and measure the height from the toilet bowl to the water’s edge. Add this value to the 60 seconds number, then multiply it by 3.6 (the number of gallons per minute).

For a better understanding, let me give a simple example. Suppose you measured your toilet at 14 inches in diameter.

It took 27 seconds for all of the water in the tank to drain out of the bowl and down into an outlet pipe under a sink, then 27 seconds – 60 = -33 seconds left over = 2.6 gallons per minute multiplied by 3.6 = 9 gallons per minute flow rate out of your toilet when it’s flushed.

Read our blog how does a toilet flush system work for a better understanding about the flushing mechanism of toilet.

How Much Water Does An Old Toilet Use While Flushing?

How much water does an old toilet use while flushing? It’s a question that probably crossed your mind at some point. We’ve all been there: standing in front of the bathroom sink, you hear the toilet flush, and you think, “Gosh, that sounds like a lot of water.”

So let’s get down to it: How much water does an old toilet use while flushing?

An old toilet uses 5 to 7 gallons of water per flush. But you already knew that, right?

It’s a common fact that we’ve all heard. We’ve seen it in commercials and on the internet: an old toilet can use as much as 5-7 gallons of water, and that’s to get rid of a tiny amount of waste.

How Much Water Does Low-Flush Toilets Use While Flushing?

How Much Water To Flush A Toilet

Low-flush toilets use less water than regular ones, but they still use some.

You’re not alone if you’re concerned about the amount of water your toilet uses. Americans use more than 2 trillion gallons of water daily on their toilets alone. That’s a lot of water!

But if you think that low-flush toilets are the answer to our nation’s ever-increasing water shortage, you may be surprised to learn how much water they use. Here’s what you need to know:

Low-flush toilets use about 1.6 gallons per flush (GPF), which is less than half of regular toilets (some can go up to 3 GPF). So that means a low-flush toilet will use between 1 and 2 gallons less every time it flushes than a regular one. 

If it’s been years since your last home improvement project, this could be the thing you’ve been looking for.

How Much Water Does Ultra Low-Flush Toilets (ULF) Use While Flushing?

Ultra low-flush toilets (ULF) use about 1.6 gallons of water per flush. That’s almost half what traditional toilets use, which are 3.5 gallons per flush.

Just like me, you might be wondering how much water it takes to perform a complete flush and why ULF toilets only use 1.6 gallons for the whole process.

The answer is that ULF toilets have a dual-flush button that allows you to choose between a full or partial flush, depending on what kind of waste you’re flushing down the toilet. A full flush uses 1.6 gallons of water; a partial flush uses 0.8 gallons of water.

If you want to reduce your household’s environmental impact by using less water while flushing, consider switching out your old toilet with an ultra low-flush model.

How Much Water Does High-Efficiency Toilets (HET) Use While Flushing?

How Much Water To Flush A Toilet

The amount of water a high-efficiency toilet uses while flushing depends on how you use it.

When installing a HET, you’ll want to run it twice to clear out any remaining residue from the old system. This can use anywhere from 1.5 to 8 gallons of water.

After that, you use your HET like a conventional toilet using about 4 gallons per flush (GPF). But if you’re using a dual-flush system, which allows you to choose between 1.3 gpf and 0.8 gpf depending on how much water is needed for the job.

Then it will use one gpf when flushing solid waste and 0.8 gpf when flushing liquid waste.

How Much Water Does Dual-Flush Toilets Use While Flushing?

How Much Water To Flush A Toilet

The amount of water used by dual-flush toilets depends on the type of flush you choose.

For example, if you use the full-flush setting, your toilet will use about 1.6 gallons per flush (GPF). On the other hand, if you choose the half-flush setting, your toilet will only use about 0.8 GPF. So using a dual-flush toilet can reduce your water consumption by up to 50%.

Some people are hesitant to switch to a dual-flush toilet because they worry they won’t know how much water to use in each flush.

But this is easier than it sounds: remember that each flush uses less water than a standard toilet.

Read out our blog To know How To Flush a Dual Flush Toilet properly.

How Much Water Does A Leaking Toilet Consume While Flushing?

A leaking toilet can waste a lot of water. A leaky toilet can waste anywhere from 200 to 300 gallons daily, about 10 percent of the average household’s total use.

This can add up to a lot of money over time—and it’s not just your wallet that loses out when you’re paying for a leaky toilet.

The water used by your toilet will be wasted whether or not you pay for it, and even if you don’t notice any leaks, the water could still be escaping and costing you money.

Well, I was pretty shocked after knowing this. As we all know, the average toilet uses about 3.6 gallons of water per flush, and a leaking toilet can use more than twice that amount.

A leaking toilet can waste up to 15 gallons of water every hour. That’s enough to fill over 50 pails.

The average household uses up to 200 gallons per day. A leaking toilet will use as much as 25% in a single hour. (wow, a significant loss, right?)

If you have a leaky toilet, I must suggest you fix it immediately because not only is the cost of water wasted money—it’s also wasted energy.

How Much Water Does An Automatic Toilet Use While Flushing?

How Much Water To Flush A Toilet

The amount of water an automatic toilet uses to flush depends on the model and type of toilet. Some models use more water than others, but all use less water than a traditional toilet.

Automatic toilets use about 1.6 gallons of water per flush, and manual toilets use about 1.1 gallons per flush, which means that switching over will result in an immediate savings of 0.5 gallons per flush—or around 20% less water than your current toilet uses.

To know more about an automatic toilet read our blog How Do Automatic Flush Toilets Work.

Ways To Save Water 

Flushing the toilet is necessary for any household, but it can be a waste of water. Luckily, there are plenty of ways to reduce water consumption during this daily task.

1. Flush only when necessary. If you don’t need to flush your toilet, don’t! It’s better to hold it until you can dispose of it properly.

2. Consider installing a low-flow toilet with less water per flush than traditional models.

3. If you have an older model toilet that needs repairs, consider replacing it with a newer version instead of repairing it because repairing older toilets can use up more resources than installing new ones—and they may not even work as well as they once did.

4. Choose the right toilet for your home. If you have a single-family home or a small apartment, choose a 1.6 GPF (gallons per flush) toilet. If you live in an area where water is expensive, you may want to consider a dual-flush toilet that uses less water than a 1.6 GPF model.

5. Make sure that the flapper valve is not damaged or cracked—this will cause it to leak! If your flapper valve is broken, replace it immediately.

6. Check your toilet tank lid every few months to ensure that it’s still appropriately sealed—if it isn’t sealed tightly enough, you could lose up to 30 gallons of water daily.

Learn to flush a toilet when you are run out of water through our blog How To Flush Toilet If Water Is Off.

Final Thought

In the end, I must say that knowing how much water to flush a toilet can save you from paying an extra cost. It is essential to flush toilets properly to ensure that all the water is flushing away correctly.

Proper flushing can help to prevent build-up and bacteria from growing, as well as reduce the amount of water that needs to be flushed down the toilet.


How much water does a toilet flush use litres?

The average full flush toilet uses about 11 litres per flush, which is a significant amount of water when you consider how many times it is used in a day.

How many litres of water does it take to flush a toilet UK?

A big flush, typically used for solid waste, uses around six litres of water. On the other hand, a little flush – is only half that amount, using around three litres of water.

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