Advice on how to close a cleanout plug

The sewer line has a wye with a 4" clean-out plug. The plug came off and won't go back on. I purchased the Cherne 270188 clean-out 4" mechanic gripper plug (black). It was too big. So then I bought the Oatey 33403 plug (red) and that was just too big. I started to file the sides, but my file is very fine, so I stopped and will get a better file tomorrow.

On a side note, the clean-out plug is located in a really tight space, so I don't have room to apply more force. A couple of inches from it the vent pipe goes up, which you can't see in the pictures. If anyone can suggest a simpler solution it would be greatly appreciated.

I don't know why the rest of the pictures did not show, so I am attaching them here

Did you try a 3 1/2" plug?
I think 4" C.I. pipe cleanout typically use 3 1/2" threaded plugs.
A plumber would know.

It's a 4" plug. It's states it on the plug, plus the 4" plugs I purchased are about 1/8" too big. A 3 1/2" plug would be too small. The inside threads on the wye are no good. Again, the biggest issue is how tight the space is and that just behind the clean-out the vent rises. Otherwise, I believe that with a block and a hammer, I could of gotten the red plug installed.

I see you had a lead coat plug on there and you say you can't get it back on. Are you sure someone didn't just hammer it on?
Being lead coated I'd be inclined to try it.

EDIT: If those 4" expandable plugs don't fit I doubt it's 4".

EDIT 2: Also, keep in mind pipe threads are tapered.

BTW...They don't make anything between 3 1/2 and 4.

If you enlarge the picture, you can see a 4 on the square head that is sticking out of the plug. I will try to get a 3.5" plug though and see if it fits. I just saw by looking at the picture that the clean-out is connected with a fernco coupling. So I guess I was wrong and it's not a wye but a 22.5 elbow. Maybe I can dig it out and pump out the water and then just replace it with a longer elbow.

Did you loosen up your plugs by turning their nut or wing nut several turns counter-clockwise, before trying to jam either one in there?
I know, obvious, but just asking anyway.

In the picture with the blue boiler, I can’t see where the cleanout is.

It looks like your old plug has a lead wrapper around it.
I have seen where that type of plug just gets set in place, then two or three good whacks with a hammer will pack the lead enough to hold it.

Although with the Fernco fitting, you pbly won’t get a good solid whack, there will be a lot of give to the cleanout.

Maybe you can clean out the rim of the cleanout with a wire brush?

The reason I showed the blue boiler is to show the lack of space and vent pipe. Just to the right of the vent pipe is the cleanout. And yes, I loosened the nuts all the way but no go. I don't understand why these plugs won't go in. They almost go in but just miss it by a hair. And yes I tried cleaning with a wire brush. But maybe I should try again with a more abrasive brush. All I care about is plugging the hole so I won't have gases and therefore smell seeping in.

What happened originally was that it was getting really smelly in the house after we had a small flood in the basement. When I looked around I saw that the plus was inside the pit but completely off the cleanout lying on its side.

take the brass co plug to the local hardware store and get either a 3'' pvc or 4'' pvc threaded plug
then, with a wire brush, or a wire brush chucked up in your drill
clean the threads till shiny [for a sewer] and install pvc plug

3'' pvc plug is 3.5'' 4'' plug is 4.5''

disreguard above

you have a band undr the co plug
remove the band ,remove the 22 fitting and install a pvc fitting clean out plug
put the band back in place

Jeff Handy said:

Did you loosen up your plugs by turning their nut or wing nut several turns counter-clockwise, before trying to jam either one in there?
I know, obvious, but just asking anyway.

In the picture with the blue boiler, I can’t see where the cleanout is.

It looks like your old plug has a lead wrapper around it.
I have seen where that type of plug just gets set in place, then two or three good whacks with a hammer will pack the lead enough to hold it.

Although with the Fernco fitting, you pbly won’t get a good solid whack, there will be a lot of give to the cleanout.

Maybe you can clean out the rim of the cleanout with a wire brush?

Click to expand...

singing sounded good. i was surprised. enjoyed it

Yeah, there are many variables that could dictate different thread sizes.
Example:

Thanks everyone. I guess I'll just dig it out and fix it. But I have one more question what is the thing that is circled in red.

I think I figured it out. It looks like a

JONES STEPHENS
Backwater Valve, 4", No Hub Cast Iron

• MFR #: B01004