stuck cleanout plug

How To Loosen A Stuck Cleanout Plug (4 Brilliant DIY Hacks!)

Two or more clogged or sluggish drains often are the result of a blockage in your main drain. Unfortunately, you might find yourself up against a fused or stuck cleanout plug when you try to access it.

But don’t worry, I’m going to show you how to find the cleanout to your main drain and loosen that plug so you can remove the blockage.

What is a Main Drain Cleanout Plug?

A cleanout plug is a cap that covers the access point into your main drain line. Often, these main drains are old and made of cast iron. Over time, the parts rust, resulting in a stuck cleanout plug.

These types of caps can be found throughout your home’s plumbing system, on basement floor drains, and the main sewer pipe that exits your property.

stuck cleanout plug - main drain access in basement
This is what a typical main drain cleanout looks like. It is most often attached to a 4-inch pipe. The plug is the lid (or cap) at the bottom of this photo. Notice the squared-off nut that needs to be turned to unscrew and remove the plug.

Where is the Main Cleanout Located?

The main cleanout is usually near the bottom of the soil stack, in the basement or crawlspace, close to where the stack makes a 90-degree turn to leave the house. It’s at this point (the turn) that the stack becomes your main drain. It slants toward a public sewer or private septic system.

In warmer climates, or in houses without basements, the cleanout may be outside, above the point where the main drain leaves the foundation.

stuck cleanout plug - located outside and inside house
Typically, as shown here, you’ll find your main drain’s cleanout located in a basement or crawlspace. If you don’t have either of these, look for the cleanout outside, usually somewhere near the foundation.

How to Loosen & Remove a Stuck Cleanout Plug

Okay, now that you know what a cleanout plug is, and where it is, here is a sequence of instructions (from easiest to most difficult). You might not need to try all of these, but one of them will surely fix your problem.

1. Preparing to Remove a Stuck Cleanout Plug

  • Before attempting to open the stuck cleanout cap, either shut off the main water supply or do not use any water in the house. Allow water to drain out of the system, preferably overnight, so that water does not pour out after the cleanout plug is off.
  • Have a mop, rags, pipe wrench, large metal file, and bucket ready. Depending on which solution below works best (we recommend you try them them one at a time), you might also need an adjustable wrench, a cold chisel, and a hammer.
  • If the cleanout plug is metal, it will probably be stubborn to remove.
  • Apply penetrating oil to the threads, and wait overnight before trying to remove it.
5 gallon bucket - plumbing emergency
Make sure to place a bucket under the cleanout plug while you’re working on it. You’ll also want to be prepared with cleaning supplies like rags and a mop.

2. Removing a Stuck Cleanout Plug

  • Loosen, but do not remove, the plug with a large pipe wrench.
  • If the nut has been rounded off from previous repairs, first file it square with a metal file. Some cleanouts have a metal cover secured by two brass bolts. Too loosen and remove them, apply penetrating oil, wait a few minutes, and use an adjustable wrench to loosen the bolts.
  • If it still does not loosen, go to the next step (#3) below.
  • If it does loosen, let some of the trapped water ooze out into your bucket. Open the plug a little at a time so you don’t have a huge rush of water on the floor.
  • With the plug finally removed, clear the blockage with an auger or garden hose (use either to remove the blockage).
best wrench for plumbers - 12-inch pipe wrench
A large pipe wrench, and penetrating oil, will come in handy when unscrewing a cleanout plug.

3. Loosening a Stuck Cleanout Plug with a Hammer and Chisel

  • If the plug remains stubborn, place a cold chisel on one edge of the nut and tap it firmly counterclockwise with a ball-peen hammer. Then move to the next face.
  • Continue hammering until the stuck cleanout plug is loose enough to turn with a wrench.
  • If the nut remains stuck, move on to the next sttep (#4).
stuck cleanout plug - use hammer and cold chisel to remove
If penetrating oil doesn’t work to loosen your main drain cleanout lid, try a hammer and cold chisel.

4. Loosening a Stuck Cleanout Plug with Heat

  • If the cleanout plug remains stuck, it likely has rusted in place.
  • Try burning off the rust around the plug with a propane torch.
  • The heat needed to loosen the cap dissipates quickly, so hold the wrench with one hand while you move the torch over the rusted fitting with your other hand.
  • Move on to the next step (#5) if this doesn’t work.
stuck cleanout plug - loosen with heat propane torch
If the cap is rusted onto the pipe, you can try burning off the rust with a propane torch. If the cap is anywhere near materials that can burn, place a heat shield between it and the flammable material.

5. Loosening a Stuck Cleanout Plug by Breaking it

  • You might not feel comfortable with this step. Let’s face it, most people have a fear of breaking things that aren’t meant to be broken. However, if the cleanout plug is still stuck, you’ll have to destroy the cap and replace it with a new one.
  • Using a power drill with a 3/8-inch metal bit, drill a ring of holes within 1/4 inch of the edge of the plug.
  • With a hammer and chisel, know out the center of the plug, then the pieces between the holes.
  • Do not let the pieces fall down the main drain.
  • Replace the plug with a new one after you have unblocked the clog. You can find a new plug (cap or lid) at a plumbing supply center (take some photos with you of the damaged cleanout) or hardware store.
stuck cleanout plug - drill holes and break with hammer
You might have to take the drastic step of breaking the plug and replacing it with a new one. Make sure you use a drill with metal drill bits before hammering. The best drill bit to use for cast iron is a cobalt bit with a 135-degree point angle. Or use a gold-colored titanium nitride bit. But any high-speed steel bit will work. Just be sure to wear safety glasses.

Final Thoughts

Sure, this DIY job is doable. But it can be a bit intimidating if you don’t have an intermediate level of plumbing experience. So, you might want to have a friend assist you.

The key is to be patient. A stuck cleanout plug can be extremely difficult to remove. And it requires a good deal of muscle.

But if you stick with it and follow the steps, as shown above, you will be able to remove it. And from there, using an auger to clear out, or garden hose to wash out, the blockage will be relatively easy. It will also save you an expensive call to your plumber.

Call 1-Tom-Plumber

Don’t hesitate to contact us here or call us at 1-Tom-Plumber (1-866-758-6237) if you need help opening any cleanout or clearing out any type of sewer line.

1-Tom-Plumber’s certified team of plumbers and drain technicians respond immediately to any emergency plumbing, drain cleaning, or water damage problem. We also handle the excavation of underground water lines and sewer main lines. Our immediate-response team is available every day and night of the year, even on holidays.

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