Upstairs toilet runs when downstairs is flushed

What is going on with my house?! First, the downstairs toilet stopped working, and we had to use the upstairs one, and now the upstairs toilet is constantly running! 

We’ve tried flushing both toilets simultaneously, turning off the water supply, leaving the lids open…then sometime after, it seems to be working. 

But, again…

The upstairs toilet is running when the downstairs toilet is flushed. It has been happening for a while now, and it’s really getting on my nerves! I’m not sure what to do about it.

Why does the upstairs toilet run when the downstairs is flushed?

The main reason is Siphoning effect of the plumbing system.

The water rises in the pipes because of the siphoning effect. When you flush the downstairs toilet, the water in the bowl creates a vacuum that sucks water up from other parts of the system.

· This causes a rush of water to go into the upstairs toilet tank, which causes it to overflow and run.

The fix: Just open the upstairs and downstairs valves (or open the closest main shutoff valve if there is no individual shutoff for each toilet). 

You can find them on pipes under or behind both toilets. Then, shut the valves again until you are through with the problem.

If the downstairs valve is corroded or damaged, it’s time to install a new pair of valves.

Other Possible Reasons for an upstairs toilet runs when downstairs is flushed-

· The causes of upstairs toilets runs can be attributed to many different things. One of the most common reasons for this is that the water pressure in the upstairs bathroom is not as strong as the water pressure in the downstairs bathroom. 

This can be caused by various factors, such as a clogged toilet or shower in the upstairs bathroom or a faulty water pump. 

· Another common reason for upstairs toilet runs is when there is a leak in the plumbing system. This can be caused by various issues, such as corrosion, a faulty seal, or a broken pipe.

upstairs toilet runs

Some of the steps to inspect an upstairs toilet runs when downstairs is flushed are below:

1. If you find you have a leak in your plumbing system, you will want to first check the upstairs toilet, as this is where you are most likely to find it.

2. You can do this by checking if the water is constantly running. If the toilet will not stop flushing, it probably has a leak.

3. If the water is not constantly running, you will want to check and see if there is a pressure drop.

4. To do this, simply flush the toilet on both house floors and check to see if there is a pressure difference. If there is, the upstairs toilet probably has a leak.

5. If you have confirmed that the upstairs toilet does have a leak, it is time to find where the leak is. You will want to remove the tank lid and check for a crack or any signs of water damage.

6. If you do not see any water damage, you will want to check the flapper valve. This rubber piece allows the waste to enter the toilet bowl. You can check for leaks by placing a little bit of food coloring in the tank and seeing if it is present in the toilet bowl when the toilet is flushed.

7. If you do not see any signs of a leak, you will want to check the toilet’s base.

8. If you do not see any water damage or signs of leakage, the flushing mechanism is likely an issue. You can either try to repair it yourself or contact a plumber to assess the issue if there is.

9. However, if you see evidence of water damage in the tank, you will want to replace the flapper valve. This is a relatively simple procedure that will not require you to hire a professional to fix it.

Read More- Upstairs Toilet Keeps Clogging | How to Deal With It

How to tell if the upstairs toilet is leaking?

It’s good to know the signs and symptoms of toilet leaks because those little drips can add up to big bucks over time.

Some leaks are obvious, but hidden toilet leaks can be more difficult to find. If you’ve had your home’s plumbing checked and it passes inspection, and if your water bill shows no obvious changes, it’s time to do some detective work.

Here are six common signs of a toilet leak:

1. Your toilet runs constantly or frequently. 

Suppose you hear a running or gurgling sound from the toilet tank. The flapper valve may be broken, allowing water to flow constantly into the toilet bowl. 

A faulty pressure-assisted flush mechanism can also cause this problem.

2. Your toilet bowl never fully refills after a flush.

If you notice that it takes several minutes for the water to rise in the bowl when you flush, there may be a leak from your valve or supply tube.

3. You hear running water sounds when nobody uses any water anywhere in the house. If you hear those sounds, it could be a leak from the supply tube to the toilet tank.

4. Your water bill starts to spike.

A sudden increase in your monthly water usage is a red flag that something’s wrong. If you use your meter to test for leaks and find nothing, there may be an undetected leak in your home.

5. Your toilet bowl is stained with rust or minerals.

Suppose water inside the tank evaporates and leaves minerals and sediment behind. In that case, it could be dripping into the bowl from underneath the rim of the tank. 

A slow leak from around the bottom of a toilet can also cause this problem.

6. You hear gurgling sounds coming from your toilet.

If you notice any of these signs, it may be time to call in a plumber or contact the manufacturer for further troubleshooting steps.

What to do if your upstairs toilet runs when a downstairs toilet is flushed?

If the upstairs toilet is running when the downstairs toilet is flushed, the drainage system’s most likely cause is a blockage. 

In rare cases, the blockage might be in the upstairs toilet itself. If this is a new installation with a dual flush valve, make sure it’s correctly adjusted as outlined in the instructions.

If there is no blockage or adjustment problem, two other possible causes are:

There is no water supply to the downstairs cistern because the water inlet valve is defective.

Water leaks into the surrounding area when the upstairs cistern fills, causing a siphon effect that runs water from the downstairs cistern into the drainpipes.

The plumber will need to check and replace parts such as inlet valves and spindles if necessary.

How to fix when an upstairs toilet runs while the downstairs is flushed? 

If the downstairs flushes and causes the upstairs to run, this will indicate a blockage in the downstream piping. 

This could be because of various reasons, such as something stuck in line or simply reduced flow due to old pipes. 

The first thing to check is if there are any blockages in the line. If there are no other ways to find out if it’s an internal clog, the only way is to completely remove all of the downstream piping and see if it still runs during flushing. 

If this fixes the problem, then replacing old pipes will be needed.

Wrap up On Upstairs toilet is running while Downstairs is flushed

The upstairs toilet is running. You need to find out the problem and fix it before my family gets home. 

If you’re in a similar situation, do it yourself. And always shut off the water supply to the upstairs toilet to prevent further leakage.

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