Full bathroom remodel, part 3: plumbing updates

Jim Mallery | Improvement Center Columnist | March 2, 2015

Third of an eight-part series on bathroom remodeling

(The first and second parts of this series explain how to demolish your old bathroom.)

What would a bathroom remodel be without a little plumbing work? Very likely, you will need to make changes both on the supply side and the drain side.

Your plumbing is one area to tread cautiously, because if you make a mistake, you could be treading water. You might be a die-hard DIYer, but there is no shame in calling a plumbing contractor if your plumbing confidence is a little squishy. If you do choose to do your own plumbing, here are some precautions.

Supply side: tips for avoiding catastrophe

You are probably going to upgrade the bathroom fixtures, which means removing the old water-control valve and soldering the new one to your copper pipes. Usually, this can be done with only minor adjustments to the existing pipes.

Cut plumbing pipe for bathroom remodel

Cutting pipe: A stubby pipe cutter lets you cut copper pipe in tight wall spaces. Here the old shower valve is being removed. The top pipe, which leads up to the showerhead, will be unsoldered with a torch, rather than cut, to preserve the length of the pipe.


Old plumbing valve removal

Remove old valve: With a couple of minutes of heat to the joint, the pipe to the showerhead will pull off.


Soldering a new plumbing valve

Valve installed: The new shower valve is installed. The char marks on the studs were from the original installation.


 Valve anchored for bathroom remodel

Valve anchored: The new valve and showerhead fitting are anchored to 2-by-4s.

Caution 1: Because you are torching amongst the studs and drywall, be very careful. With a spray bottle, dampen the flammables. Buy a heat-resistant cloth at a plumbing store or at The Home Depot -- in the tool area where they sell propane torches -- that you can drape over the studs. The cloth will cost about $10 for a square foot.

Caution 2: Soldering at the valve can damage the ceramic disk inside the valve. Usually, you have a threaded fitting that solders onto your water pipe and screws into the valve. Solder the pipe to the fitting first, then thread it onto the valve to keep the intense heat from hitting the valve. Other fittings should be far enough away from the valve to safely solder.

Caution 3: You cannot have any water sitting in the pipe when you unsolder it: You can hold the torch to the fitting endlessly, but it will not heat enough to break the solder loose. Try jiggling the pipe enough to get the water to drain, but if it doesn't, you might have to either cut the pipe or drill a hole to drain the pipe. Replace it with new pipe when you reconnect the fittings.

Caution 4: You may have fantasies of a multi-jet, full body-spray bathroom fixtures to replace the pathetic old single shower head. But most showers are supplied by ½-inch pipe -- not enough to power many of the body-jet systems. Before you buy a Titanic spray system, ask to be sure that it works satisfactorily with ½-inch pipe -- or make sure you have ¾-inch pipes into which you can tap.

Drain side: installation dos and don'ts

If the old trap was glued to the old fiberglass stall and had to be cut off -- - or if you are changing the shape of the shower and want to move the drain hole -- install a new drain flange and trap, using ABS (black plastic) pipe. ABS is easy to install, but take some precautions.

Underside of plumbing installation

The new trap and drain base are glued into place and the base has been screwed to the new subfloor. The rotten wood has been removed from the joist and a new joist “sistered” onto the other side. The black ABS pipe running alongside the joist is a vent pipe.


Gluing ABS

An example of gluing ABS, here the sink drain pipe, gets coated with adhesive. The fitting, also with a thin coating of glue, will be pushed onto the pipe.


Caution 1: Cut the pipe squarely (a power miter saw -- chop saw -- is great for this) and remove all burrs with sandpaper. Wipe the pieces clean.

Caution 2: Coat both pieces with the cement, but use the cement sparingly in the female side of the connection.

Caution 3: Push the pieces into position rapidly -- the joint will set quickly and you won't be able to readjust. Continue pushing the joint together for a minute or so to keep the pieces from springing back.

Caution 4: If your fittings have any tricky angles, first dry-fit the joint -- it won't go all the way together without the glue in it, but you should be able to get it at least halfway. Make a line with a marking pen across the joint, or run a piece of tape across the joint and slice it, then pull the joint apart. When you push the glued joint together, simply line up pen lines or tape.

Next, part 4: building your shower stall

About the Author

Jim Mallery, a semi-retired journalist and onetime registered contractor, has extensive experience remodeling, repairing and rebuilding homes.