Plumbing in the Home/Washer hookup box
I was doing some repairs, and disconnected the washer intake and drain hoses from the box on the wall (see pic). I noticed the faucets had a little drip, very minimal, which had been unnoticed while the hoses were connected b/c it'd probably dry inside the hoses or something.
I thought the drip was harmless b/c the box has a drain pipe and the lower edge is high. Actually the dripping was sliding down the faucet's "body". But was I wrong!? As the walls were to be painted, I left the washer unhooked for a few days, and when I came back, there was water (not much) coming from inside the wall and into the floor of the A/C closet (which shares the wall with the washer box). I think the holes for the faucets and the drain pipe in the box are NOT sealed. Is this the way these boxes are supposed to be installed?
IMHO a better installation would be if those holes were sealed around the faucets and the drain pipe. This was a drip, but it could have been worse. When I see plastic and that the drain is connected I expect it to be water safe. What are your thoughts about this? If they better be sealed--as I suppose--how can I seal them?
These washer boxes are not designed to be watertight. They are merely a way to set the water supply valves and drain inlet flush with the wall. As you can see, once you remove the trim flange, the bottom of the box essentially flat and not sloped towards the area of the drain. The center hole is not actually a drain, it is just a place to bring up the drain pipe from below.
The leak that you are experiencing is likely coming from the "bonnet nuts", the part that seals around the stem of the faucet. Those can be tightened up a bit to stop this leak. Washer valves are not typically open and closed very often although they should be. If you actually read the directions on your washing machine, it recommends that you turn off the water in between uses.
Because they are not used, the bonnet packing "takes a set" and then when you do operate the valve it breaks that seal. Simply tightening the bonnet nuts a little bit will usually handle it.