My front loading washer and dryer are 39-inches tall and the outlet box is 39-inches high (from the floor to the bottom of the box) so it's in plain sight and easily reachable. We're getting new front loading machines that are on pedestals making them 53-inches tall so the box will be completely hidden and impossible to reach without a step stool and reaching way down behind the washer. Should the box be moved upward to be visible and accessible?

What does it say in the installation manual about the drain pipe installation? They usually tell you where it needs to be placed.

We haven't purchased the washer/dryer yet so we have no manual. I talked to someone in the plumbing department at Lowe's who said to raise the bottom of the drain box to the height of the top of the washer (height differs from 51 to 53 inches depending on brand) for accessibility and that doing so wouldn't cause any problems with drainage for a front loader with or without pedestals or a top loader. Accessibility for turning the faucets on and off for any number of reasons trumps the lower height and inaccessibility. I'm still looking for a more authoritative answer. Right now the drywall is off so relocating the drain box is easy.

You want the drain box at or above the level of the washer. If it is below the water level, it will siphon out and the washer won't fill. You can always pump the water up a foot or more above the rim. Since the drywall is out, move the box up so it is easily accessible. If the supply piping is copper, it's a little harder since you will have to solder. If CPVC, the extension is easy, after the water is off. If the piping is PEX, you will need to cut the connector, add a connection barb and then extend the piping. You will also need a compression tool. The drain is either copper or PVC and would require the needed extensions. I would also look at the manual in the store before buying the washer. That way, you will know what you need to do.

I'll raise the drain and extend the copper lines. Thanks.