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Does a Dishwasher Need a P Trap? (Quick Answers)

It’s great to have a P trap in your drain pipe to keep sewer smells away. Our dishwasher connects directly to the sewer system. And we all know how bad sewer smells are. So how important is a p trap in a dishwasher? Here’s what you need to know.

Does a dishwasher need a p trap?

The dishwasher must be equipped with a P trap. It allows the dishwasher to be free of the unbearable odor and toxic gasses associated with sewage. The P trap is positioned on the drainpipe of the dishwasher. The dishwasher could become unhygienic without it. 

There are many appliances connected to the drainpipe direct sewerage. The sewerage stinks a lot because there’s a lot of dirt. We can protect ourselves from bad smells by using physics.

A p-trap is a pipe bent in the shape of a p. These are usually installed with sinks, dishwashers, toilets, and showers. This trap catches water underneath. Which acts as a seal. No smell from sewerage can penetrate the clogged water and get into the dishwasher or sink. 

There’s an outside vent for that. As a consequence, even if dirty water is always flushed down the sink drain, it cannot emit an odor. Dishwashers connect to the sewer system, so a P trap is necessary to prevent odors from returning

Modern sinks, dishwashers, toilets, and anything that goes into sewerage are always equipped with a P trap to prevent the accumulation of sewage smells. Due to its importance, the federal government mandated the installation of P traps in the sink and dishwasher. 

4 reasons why dishwasher needs a p trap

The dishwasher successfully cleans our dishes. The dirty water is then deposited in the sewer via the drainpipe. Keeping your dishwasher connected with sewerage hygienic is easy with a p trap. Here are some reasons why.

Keeping sewage gasses at bay:

The main purpose of the P trap is to prevent sewer gas from reaching appliances. There is also a similar p trap attached to the sink and toilet. Because sewerage is so unpleasant. No one wants this stench in their dishwashing machine and kitchen. 

The water in the trap prevents this stench from entering the dishwasher. Using a dishwasher without a p trap will cause your appliances and dishes to smell bad.

Plumbing code:

P traps installations have been made mandatory by the government in plumbing codes for assembling hygienic sewage systems. 

In this case, you still have to install it if it’s required by your local plumbing code. You can also use an S trap instead of a p trap. However, since there’s no outside vent for the S trap, sewerage gas can get inside

Protects against poisonous gasses:

The sewerage system produces large amounts of toxic gasses. Examples include ammonia, hydrogen sulfide, and sulfur dioxide, as well as methane and industrial solvents. The gasses are so toxic that they can perish the individuals if they enter the body. 

These low-cost accessories protect sinks and dishwashers from this toxic gas. The P trap keeps toxic gasses out.

P traps can entrap solid metals:

There’s a P trap on the drainpipe of the dishwasher and sink. If an expensive object is accidentally flushed down the drain, it does not go to waste. Instead, it becomes trapped in the trap below. 

Consequently, there is a chance to recover the expensive item even if it is accidentally dropped into the sink. This is known as a P trap bonus.

Where is the P-trap on a dishwasher?

The trap will be at the bottom of the sink drain pipe if it’s connected to the dishwasher drain pipe. The garbage disposal is usually installed with a dishwasher and sink. It will come with the garbage disposal pipe.

When the dishwasher is installed separately from the sink. You’ll find the P trap at the bottom of the pipe coming out of the air gap. It’s easy to find a P trap because it looks like the English letter P. If you can’t find anything like the P trap, then look for something like the S trap. 

People often use the S trap rather than the P trap.

Do dishwashers have a built-in trap?

There is no P trap built-in to the dishwasher. You usually have to buy it when you install it. And you have to install it with the dishwasher’s drain line. You probably already have a p trap installed if you connect the drain pipe sink to the dishwasher. 

That is because the sink always has a p trap. Therefore, it would not be necessary to have more than one. It is sufficient to have just one. Dishwashers do not come with a P trap. You will have to install it separately. 

It enables you to protect yourself from toxic gasses, food contamination, and hygiene issues. 

Can a dishwasher drain after the P-trap? 

The dishwasher cannot drain after the p trap. In case the dishwasher drain pipe is added after the P trap, it won’t be of any use. The stench of sewage will fill the dishwasher without any obstructions. The sequence is as follows:

Dishwasher> Drain Pipe> air gap> garbage disposal> P trap> pipe and Outer vent> sewerage.

So the drainpipe will lead from the dishwasher to the air gap. Those pipes will reach the garbage disposal. The pipe coming out of the disposal unit will then go into the P trap, and then into the sewer system. It will have a vent attached to it as well.

The sequence cannot be altered. That means you can’t add a drain line after the p trap. By doing this, the P trap will be unused and the toxic gas will enter the dishwasher. However, you can’t put a p trap even before the disposal unit. 

Food particles will get into the P trap from the dishwasher. Therefore, you must follow the mentioned procedure to obtain the P trap that you are using.

How do you p trap a dishwasher? 

P-trapping the dishwasher is not difficult. This requires drainpipes, hose clamps, air gaps, garbage disposals, pipes, P traps, outer vents, pipe cutters, and screwdrivers. 

Continuing the installation process is as follows. (Dishwasher > Drain Pipe > air gap > garbage disposal > P trap > pipe > sewerage)

Connect the air gap to the dishwasher:

Start by cutting the drainpipe to the desired size. Plug one end into the dishwasher. Hook the other end up to the air gap. Attach the air gap to the sink flange. Connect another drain pipe to the air gap. The other end goes to the sink or garbage disposal.

Mount Garbage Disposal:

There’s a place on the garbage disposal where the dishwasher drain pipe goes. Just hook it up. Attach the disposal to the sink. Make sure the disposal is connected to electricity. Make sure another drain pipe is connected to the disposal.

Installing the P trap:

Connect the pipe coming out of the garbage disposal to your p trap inlet. The inlet and outlet sides are marked on your p trap. The curved side of the P should be at the bottom. Getting this right is crucial. Next, connect another pipe to the outlet. 

This pie will go outside and get attached to the outside vent. It will then get to sewerage. 

P trap dishwasher without sink:

You can also connect the dishwasher to the sewerage without connecting it directly to the sink using the same procedure. There will be no connection between the sink and garbage disposal. The pipe from the air gap will lead to the garbage disposal. 

Following that, it will enter a P-tarp, then a P-trap into the sewerage system. 

Dishwashers may also have direct connections with P traps without having any garbage disposal. In this case, the dishwasher’s drain pipe will come into contact with the air gap then the P trap. 

The only thing to remember is that if you already have a P trap attached to your sink, you can install a dishwasher with it as well. You won’t need another trap for this.

Final Thought

A P-Trap can prevent the return of gas and odors from sewage to the toilet, sink, and dishwasher. The dishwasher is required to have a P-Trap installed. Plumbing codes recommend this as well. You should install a p trap if you have a combining sink and dishwasher.