How do I seal an unused washing machine drain?

Question

I have an unused washing machine drain in part of my house and it's started to smell because (I assume) the water in the u-pipe has dried up. My objective is to stop the smell and I guess the only way to do this is to seal this. I want the seal to be temporary in case I want to use this again in the future. I've tried putting scotch tape over the hole but it won't stick and I'm afraid that tape in general will come loose at some point in the future.

Before I go off and buy some heavy duty duct tape or the like does anyone have some obvious answer I've missed?

Answer 1

Pour some RV antifreeze into the trap. It won't evaporate quite as fast as water, and will stop the sewer gas until the rest of this is sorted out.

A sink stopper won't do what's needed here. A test plug goes in the pipe, which is probably no more than 1-1/2 to 2 inches. The seal is formed by winding up the screw so that the rubber seal is expanded against the walls of the pipe. I have no idea where you think you can stick a 3-1/2" stopper in the washing machine box you've pictured. You'll need to cut the hole for the drain properly if, as it appears, it's not really matching the hole in the pipe.

Answer 2

Option 1:

How about a rubber stopper?

You might need to file up the hole a bit to make it more round and shove one in.

They have some larger ones if you require it.

Option 2:

A big wad of Blu-tack.

Option3:

Expanding foam. Sounds bad... but what I'd do is scrunch up a piece of newspaper and push it into the end an inch or so down the pipe. Then squirt a little expanding foam into it to form a plug. The newspaper will prevent the foam going down the pipe too far. It should be easy to clear it out later.

Answer 3

Maybe with a commodity stopper like this?