The great thing about a bathroom remodel is that it often results in an increase in the value of your home than is greater than the actually costs of remodeling. Whether you want more space or you want a new traffic pattern in the bathroom, one thing is inevitable--the need to relocate the plumbing. Before you start tearing out the fixtures, make sure your new plan is workable.
Determine the new bathroom configuration to suit your existing home drainage system. While it's possible to move almost any large fixture, beneath the bathroom floor are supporting joists that you should not cut in order to install new drains. Design your new configuration so that the new drainpipes run parallel to the joists and between them.
Determine the fixture setbacks. Check your local building code first. If you are required to pull a permit for the bathroom remodel, you will probably have to adhere to setback measurements. This just means allowing adequate room on all sides of your major fixtures. Follow standard code if local code is not available (see Resources below).
Provide future access panels. While sink plumbing is usually accessible in the cabinet below and toilet plumbing requires only lifting the toilet from the floor flange, it's a different story for bathtub or shower plumbing. Should there ever be a problem with your bathtub or shower plumbing; the only feasible access is often from the adjoining room, hopefully in a closet or inconspicuous place. If a sidewall in the bathroom is available, plan the access panel there.
Turn off the water supply before you begin, this is usually located in a utility room. Some older homes have only a meter shut off outside. Remove the fixtures and disconnect the water feeds and drains. Cap and seal all old water feeds. You can crimp copper tubing or purchase special caps for PVC tubes.
Install your new water feeds, bringing the hot and cold water directly up from below, between the studs. Avoid running feeds horizontally or drilling through studs. Tie into the old system if you have copper feeds or run new PEX tubing if you have a compression port system, such as Manabloc.
Allow for adequate slope on your drains. Minimum slope for waste drains is a fall of ¼ inch per every 4 feet of linear drainpipe. On a sink drain, you need at least a 2-inch pipe; a shower also requires a 2-inch drainpipe, but the toilet needs a larger 3-inch or 4-inch drainpipe. Avoid using a slope with more grade than recommended for a toilet to prevent liquid from out-running solid waste in the pipe.
Pressurize your new water feeds before placing your fixtures. Do this by capping off the ends of all the hot and cold water tubing and also capping the drains. Turn on the water source and allow the pipes to fill with pressurized water. Leave the pipes pressurized for a few hours and check for leaks before placing the fixtures and installing the fittings.
Place the new appliances and connect the water feeds and the drains. Check to make sure the hot and cold feeds are correct when you install the faucets. Check for leaks around faucets and readjust, if needed.