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How to Convert S Trap to P Trap in 4 Steps?

Recently, many states have banned the use of S traps. Because of their inefficiency and health risks. So, converting or replacing your S traps with P traps is a good idea! 

How to convert S trap to P trap?

There are a number of ways to convert an S trap to a P trap. You can use a full conversion kit to change it without any hassle. Otherwise, you have to cut the S trap, put the air admittance valve to convert it to a P trap!

We have explained the conversion above in short. In this article, we’re going to discuss all you need to know about drain lines. How S and P traps work and how to convert them! 

Let’s begin!

S-traps and P-traps: What You Need to Know?

The names of the traps are given based on their appearance. However, the difference goes beyond looks. There’s a lot to discuss in the comparison between S and P trap. The key pointers are-


S-traps were the most common type of drain lines in the 20th century. The shape of the drain was like an “S. The pipe diverted slightly and reversed back into position before going down.

In most cases, S-traps work well. However, there needs to be a constant amount of water present in the diversion. This prevents the formation of any air gaps, preventing gases from escaping.

If the amount of water dries out or reduces, problems can happen. The lack of air allows gases to pass. Thus, creating fumes and smells in your bathroom. For this reason, plumbers and regulators discourage the use of S traps.

S traps are banned in many states due to their risks. So, keep that in mind. We suggest checking the plumbing codes of your area beforehand.


P-traps initially came into being as an alternative to S traps. A P-trap has two main parts to prevent gas from leaking out. These include an air admittance valve and an extension to the drain.

The bent is placed inside a wall that goes through the roof. As a result, any fumes or gases go upwards and out of the system. Thus, preventing any risk of siphoning inside the pump. Also, this doesn’t require any additional management either.

The extension on the drain side is used to keep water in place. The extended pipe prevents any gravitational pull for the water. As a result, any chances of fumes coming out of your pipe are reduced.

You need to do some calculations before setting it up. The length of the extension must be 2.5 times bigger than the pipe’s diameter. Otherwise, it won’t fit correctly. 

Now that we’ve discussed the traps, let’s discuss how to convert an S trap to a P trap.

How to Convert an S-trap to a P-trap?

Converting an S trap to a P trap can be a bit tricky. However, with a bit of effort, you can get it done easily. The steps for conversion are-

Step 1: Remove The Drain Plug

We recommend that you remove the drainpipe before starting. Similar to replacing the main valve without turning off the water, any sudden flow of water can damage your system.

Take a set of pliers and remove the drain plug slowly. Be careful so that you don’t damage the lining of the pipe. If you have any tape on the pipe, remove them first. However, be careful of any leaks from your pipe. 

Have a foil baking pan below your pipe to catch anything coming out of your pipe. Once it’s removed, move to the next step. 

Step 2: Create Room for The Pipe

In this step, cut out a part of the valve. So that we can create space for the pipe. Take a reciprocating saw and precisely cut through the trap. Make sure you cut according to the size of the valve. 

However, be careful with the saw you’re using. If it’s not sharp enough, it’d cause a lot of trouble for you. In case you’re wondering what kind of saw to use, check our recommendations:

Product 1
Product 2

These are some of the best out there! Check them out to know more about them! 

Step 3: Place The Pipe 

Take your pipe and place it in the hole. You can choose any from the different types of PVC for as long as it’s sturdy enough. Make sure the length of the extension is at least 4 inches. Also, the length must be 2.5 times bigger than the diameter. 

The extension pipe must be connected to a vent. You can also add an air admittance valve for better control. Secure the pipe and place. You can use tape or plumbers putty to keep it secured. 

With that, your air S trap is converted to a P trap. Now set everything back together!

Step 4: Reconnect The Drain Line 

Our conversion is complete, you have to reconnect everything back together. Join the drain line to its head and secure it in place. Turn on the water to see if there are any leaks. If there are none, you’re set!

With that, we’ve discussed everything about how to convert an S trap to a P trap! 


Question: How to know if S traps are illegal in my area? 

Answer: Check for the local plumbing code of your area. If you can’t find it on the internet, contact your local plumbers and ask them. They will provide you with the necessary details. 

Question: Do I need two P traps for a double sink? 

Answer: In most cases, you don’t need two P traps. Simply tie the traps to a tee and connect them to a P trap. However, if your pipes are too thin, you might need two traps. 

Question: How close does the drain need to be to the P trap? 

Answer: The maximum distance between the P trap and the drain should be 24-inches. If the distance is too far, it’ll be troublesome. 

Final Word 

P traps are an efficient solution to several drain problems. If you have S traps, convert them as soon as you can to P traps. To help you out, we’ve discussed how to convert an S trap to a P trap in simple steps. 

We hope you find this article helpful!