Do You Need a P-Trap with a Garbage Disposal? (Explained)

Different plumbing codes prevail in different regions of the country. While some states advise that you install a p-trap with your basin, others suggest otherwise. Some regions even suggest that you should install a p-trap anywhere there is an open drain.

Yet, many people often leave confused about whether they need a p-trap with a garbage disposal. In this article, we will answer all the queries regarding that matter.

Do you need a p-trap with a garbage disposal?

Yes, you should use a p-trap with a garbage disposal. There are different codes applicable to different regions instructing how you should install the p-trap. Keep in mind that every drain will need a p-trap, including shower, tubs, and sinks. Even sinks with garbage disposals need a p-trap.

P-trap is an important part of the drainage system in a house. You will need to install a p-trap with garbage disposal. P-traps block the gas from the sewerage line from entering your home.

So it is part of the plumbing code to install a p-trap with every drain in the house. You will need a p-trap with the shower and sinks of the washrooms. Toilets will also need p-traps. And the drainage system also includes garbage disposals.

So you cannot avoid installing a p-trap with the garbage disposal in your home. It is an essential part of the plumbing process.

If the garbage disposal is attached to a sink, it will not need a separate p-trap. You can simply install one p-trap attaching both the units together. It will work just fine.

However, if the garbage disposal is installed separately, it will need its own p-trap. It is necessary to install a p-trap with every drain in the house, and that includes the garbage disposal. 

Why does garbage disposal need a trap?

P-traps are tasked with a very important function. They block any leaked gas from entering the house through the sinks or drains. So it is essential that you install a p-trap to the drains, sinks, showers, and toilets of your house.

Garbage disposals are sometimes attached with sinks, while others are set up on their own. Either way, you should install a p-trap with the garbage disposal in order to prevent any harmful gas or other substance from entering the house.

Garbage disposals need a p-trap to stop the leaks from coming into the house. The garbage disposal may seem like a unit of substantial size. But it still requires the help of a p-trap to prevent any gas from leaking into the house through the pipes underneath.

What happens if you don’t use a P-trap?

If you don’t use a p-trap properly, there can be many issues in your house that will later require plumbing attention. P-traps are essentially used to prevent any toxic or harmful gas from entering your house through the pipes of drains, sinks, showers, tubs, and more.

It is vital that you ensure the proper installation of p-traps because it will keep your home safe from any toxic gas or elements. In addition, if you don’t use a p-trap, chances are your house will stink of smells from the sewerage line running underneath the drains.

A common issue with p-trap is that it may end up being too dry after a certain period. In such a case, the gases from the sewage leak in through the pipes.

So you will have to make sure to install a p-trap with any drainage facility inside the house, including the sinks, garbage disposal, showers, tubs, and more.

And not only that, but you will have to make sure that the p-traps are installed properly, according to the codes of that particular region.

How far below the garbage disposal should the P-trap be?

While it depends on the code of a particular region, on average, the p-trap should be about 24 inches below the garbage disposal. This is applicable for other kinds of drainage systems as well.

It is essential to keep the p-trap at an appropriate distance from the sinks, garbage disposals, or drains. Otherwise, its potential may not be maximized. So make sure to follow the code of your region in determining how far below the garbage disposal should the p-trap be.

Which way does the P-trap go?

There are some plumbing codes that you will need to follow while installing the p-traps. So it is very important to know the right procedures regarding which way the p-trap should go.

Keep in mind that the p-trap is attached to other pipes underneath a sink or drainage system. It has two ends. One of them is straight and the other end is slightly curved.

Make sure to attach the straight end to the extension that is placed on the top, right underneath the sink. On the other hand, the end that is slightly angled should be connected with the pipe that is placed alongside the p-trap.

This pipe is connected to the sewer, as opposed to the sink.

Can a P trap be angled?

Yes, p-traps are generally angled. These traps are typically placed in a manner that is 45-degree angled horizontally, especially if you’re placing the p-trap under a tub. In such a case, the p-trap will need to be made of flexible plastic that does not break or crack when angled.

And generally speaking, it does not matter whether the p-trap is angled. As long as it can carry out its functions properly, the angle will not be a matter of concern.

How to install a P-trap on garbage disposal?

You will have to be careful while installing a p-trap on the garbage disposal. Here are a few steps that will help you install a p-trap on garbage disposal easily:

Prepare the sink and garbage disposal:

First of all, turn off the sink water and place a bucket under the pipes. This will make sure that there are no water leaks on the floor. Now remove the drain pipe and drain tube from the dishwasher.

Measure and cut the tube:

Now you are ready to install the p-trap. Take the tube, and measure the distance between the sewerage line and the garbage disposal tube. Cut the tube accordingly. 

Attach the nuts and washer:

Now that you have the right measurement for the tube, you can attach the washer and the nuts to the pipe on both ends.

Install the p-trap:

Now it is time to install the p-trap and bridge the gap between the waste connector and the garbage disposal.

There should be a tube coming out of the garbage disposal and another from the waster connector. And there should be two ends in the p-trap. One of those ends is slightly angled while the other one is straight.

You should install the p-trap in such a way that the end that is straight should be connected to the tube that’s coming out of the garbage disposal. On the other hand, the angled end should be connected with the waste connector.

Once the p-trap is placed properly, make sure to seal the pipes in their positions by tightening the nuts.

Does every P-trap need a vent?

Yes, every drain and p-trap needs a vent. The vents will allow the gases from the sewerage a place to vent. So the vents prevent the gases from building any additional pressure inside the sewerage pipes and help the p-trap to prevent any leakage from entering the house.

Does every drain need a P-trap?

Yes, every drain needs a p-trap. P-traps are installed with every drain as a precautionary measure. The traps will prevent any harmful gas or bad smell from entering the house through the pipes.

What size P-trap for garbage disposal?

If you’re getting a p-trap for the garbage disposal, then you can get one that measures about 1 ¼ to 1 ½ inch in diameter. Measure the diameter of the tailpiece with which you are going to connect the garbage disposal and get one that will fit. 

How do I know what size P-trap to get?

To determine what size of p-trap you need to get, you will need to identify where you are going to place it.

If you’re getting a p-trap for the bathroom, then a p-trap of 1 ½ inch to 2 inches will suffice. On the other hand, if you’re getting one that is for the kitchen, then you may need a slightly larger one.

Final thoughts

You will need a p-trap with garbage disposal. It is made compulsory through plumbing codes in many regions of the country to install a p-trap with any drain, including the garbage disposal. The trap protects the house from any leaked gas and bad odor from the sewer lines running under the drains.