Product help-Need a clean out plug/cap replacement

[Mike Montague]

I just bought this house that was built in 1969 in Chicago area. The drain system is copper and cast iron. One of the soil stack clean out plugs is not secured.

The plug has a raised head but it does NOT have male threads and neither does the pipe have female threads. There is a 4 inch rubber O-ring that sits in a recess on the plug. I don't understand how it was ever secured. There are some projections on the inside that leads me to think it used an internal clip. I've never seen that setup before. I've tried to attach pictures.

I'm looking for advice on buying a replacement plug/cover.

 

[Reach4]

Maybe there was a rod attached (welded?) across those two inside bosses, that matched the length of the wide part of the hole. Then when the cap was turned, that rod pulled the cap tight with a camming action. It did not have to be a rod, but that remaining shape on one of the bosses seems to match a rod shape.

What is the ID of the hole, widest and narrowest?

You can buy a replacement o-ring. You need to measure diameters. I would opt for softer than typical o-rings (lower durometer).

To hold that old cap in place with more compression, you could find a better strap than what you were using. I would get a 1 inch "endless" ratchet strap.

 

[Sponsor]

 

[Mike Montague]

Maybe there was a rod attached (welded?) across those two inside bosses, that matched the length of the wide part of the hole. Then when the cap was turned, that rod pulled the cap tight with a camming action. It did not have to be a rod, but that remaining shape on one of the bosses seems to match a rod shape.

What is the ID of the hole, widest and narrowest?

You can buy a replacement o-ring. You need to measure diameters. I would opt for softer than typical o-rings (lower durometer).

To hold that old cap in place with more compression, you could find a better strap than what you were using. I would get a 1 inch "endless" ratchet strap.

Right now I have it secured with a wire [ex-coat hanger] twisted tightly around the fitting and plug.

 

[Kreemoweet]

You might be able to find an expansion plug to fit the opening, similar to one of the plugs
shown on this page: https://www.grainger.com/category/p...est-plugs?attrs=Nominal+Size|4"&filters=attrs