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AC Condensate Drain Into The Sewer: Is It Good or Bad?

A direct connection between a condensate drain and the sewer isn’t great. But sitting around and ignoring it will get you nowhere. This situation should be treated with utmost importance. 

Should you be worried about an AC condensate drain into the sewer? 

A simple answer would be yes. An AC condensate line should never connect to sewage directly. This lets the sewage air enter your AC system. To prevent this, a P-trap is used by many plumbers. It prevents the air or water from going back inside. If the P-trap is missing, you’ve to install it as soon as possible.  

This is only a small portion of the explanation. Read along if you want to know more about P-traps and AC condensation lines. 

Let’s not roam around any longer and head right in- 

Should AC Condensate Drain Be Connected To Sewage Directly?  

When investigating a condensate line, you might discover a direct connection to sewage. In most cases, experienced plumbers do not make this mistake. 

But in some cases, the unfortunate happens. To clear your confusion about direct connection, yes it’s really bad for your AC system. Just how draining water softener discharge outside is dangerous for the environment. Because of the direct line, the sewer/outside gas enters the AC system. This can surely damage your AC system.

This issue is solved by installing a P-trap. Although many manufacturers may not recommend a P-trap, they do encourage people to use it. 

How Does a P-trap Work? 

The P-trap nullifies the pressure imbalance which is created within the system. It does that by preventing the condensate line from sucking air. 

A P-trap has several parts such as a ventilation line, U-shaped pipe, and drain exit. It has a simple mechanism that mustn’t be hindered during installation. 

The science behind the P-trap is very simple. The U-shaped portion of a P-trap has two pipes. They are called downward and upward pipes respectively. 

The water gets released from a higher height. So, it uses momentum to climb the upward pipe. However, the opposite can’t happen because of the upward pipe being shorter. 

As a result, there’s always water in the U-shaped area. It gets pushed to the exit when new water is released. This is how the AC system can release water without any interruption. 

Install a P-trap By Yourself in 3 Easy Steps 

Now, we’re now going to install a P-trap. If you’re already worried, well don’t be. Luckily, installing a P-trap is super easy. 

You might have to work for a whole day to fix crumbling basement walls. But the P-trap installation process will be finished within an hour or so.

Gather the Necessary Tools 

Before we start, you’ll need certain tools for this DIY installation. Rest assured! They are easy to manage and the fittings are really cheap.  

  • A bucket 
  • Rags 
  • Pipe Cutter or Hacksaw
  • A plier 
  • TorchLight (Optional) 
  • 4x Elbow Fittings 
  • 1x Tee Fittings 
  • PVC Cleaner Primer and Glue 

Manage these plumbing tools as soon as possible and we can get started! 

Step-01: Cut the Condensate Drain

In this step, we’re going to cut the pipe into two and install some fittings. But before that, you’ll need to turn off the AC system.

First, get a bucket and some rags. Because there could be water inside the pipe. Now, choose a place where you want to install a P-trap. 

Then place the bucket beneath the area you’re going to cut. You can use a pipe cutter or a hacksaw to cut the pipe. After that, drain the water out. 

Step-02: Create the U-shape   

You have to install 4 elbow fittings and create a U shape now. But you can’t just connect the fittings as they’ll be loose. 

Coat each pipe and fit it with a PVC cleaner. Apply some glue afterward. Lastly, join the pipes to the fittings.  

Now, we’re going to install the 1st fitting between the condensate and downward lines. Connect both ends of the fitting after applying the coating and glue. 

If the drain goes straight downwards, it can be used as a downward pipe. 

It’s time to get the 2nd elbow fitting. Carefully, connect it to the other end of the downward pipe. Get a short pipe and insert it into the fitting after that. 

As for the bottom pipe, it must be shorter than the upward pipe. Likewise, install the 3rd elbow fitting with the bottom pipe and connect the upward pipe.

Take the 4th elbow fitting and connect the upward and sewer lines together.  Be sure to apply coating and glue to each joint. 

Speaking of fittings, here are some of our favorite picks:

TAILONZ PNEUMATIC Male ElbowCheck Current Price
Banjo Elbow FittingCheck Current Price

Now, you can grab any fittings you want and start working! 

Step-03: Install the Ventilation Pipe 

Cut the sewer pipe again. The T part of the fitting will be inverted and a short pipe will sit on it. 

Now, connect both ends to each hand of the fitting. After that, take a short pipe and insert it into the remaining hole. 

The pipe must face upwards so that it can release air from air bubbles. Also, if you come across any sort of leakage, you can just cap off the PVC pipes

And you’re done! You’ve successfully installed the P-trap and your AC system is safe now. 

Here are some fitting kits to make your live easier:

Habitech Fitting KitCheck Latest Price
Kalolary Fitting KitCheck Latest Price

If all of these seem like a hassle to you, just hire a professional plumber! 


Question: How much does it cost to replace a condensate pump?

Answer: A condensate pump is usually priced at $45 – $50. However, if you were to call a plumber, it might take between $120 – $160

Question: What happens when a condensate pump fails?

Answer: If the condensate pump fails, the AC won’t get started. The air conditioner automatically shuts itself down to prevent a water overflow. 

Question: Does AC condensate drain need a vent?

Answer: It’s optional and totally up to you when the drain exit isn’t connected to anything. If the drainpipe is connected to a sewer pipe, you’ll definitely need a vent. 


And that’s everything we could collect and provide on AC condensate drain into the sewer.

We hope this has cleared your confusion, even if only a little bit. 

Good luck solving the issue!