Need a cap for 4" inlet flange

[Mark Gibney]

I need a cap for a plastic nominal 4" inlet flange. The OD is about 3 15/16".

It's for part of my dust collection system. I bought it online, and the site does not link to any end caps.

Screen Shot 2019-06-18 at 7.28.15 AM.jpg

I presumed a flexible end cap for a sewer clean out, the ones with the hose clamp, would fit, but they are sized about 4 1/4" ID.

I've searched McMaster-Carr and found something that might work, but I figured someone here might have a better idea.

thanks, Mark

[Paul F Franklin]

Cut a short length of 4" pvc, slip it over the flange, and then use the rubber cap you bought. If the plastic spacer is too loose, cut a kerf in it to allow the cap to compress it a bit.

[Bill Dufour]

Those Fernco fitting come in multiple 4" sizes. They make them for pvc, clay pipe, cast iron, steel, and copper. You may have to buy a coupling and make a wood plug for one end.
Bill D.

[Keith Pitman]

You might find a plumbing cap at Home Depot. There are solid ABS caps and rubber caps that might fit.

[Mark Gibney]

Paul - sounds like a plan. I'll do it tomorrow.
Bill - I checked through a lot of Fernco end caps, couldn't find one to fit.
Keith - none of the caps at the Big Box stores fit, strangely enough.

Thank you all for your advice, Mark

[Jerome Stanek]

What about a plumbing test plug

[Tony Latham]

How about a 4" drain-pipe cap shimmed with masking tape?

[Bill Dufour]

Check at the grocery store. the tall pineapple juice cans fit inside dust hose. You might use a can outside the fitting or use one inside with a flat board screwed onto one end as a cap.
Bill D.

https://www.sizes.com/home/cans.htm