Stained and old bathtubs can easily be replaced by a professional plumber.  You can even replace one yourself if you like home plumbing repair and DIY projects.  Of course, you need to make sure that the bathtub does not leak when you complete installation. If you do not, then you can end up with a wet mess that breeds mold, mildew, and rot.  Fortunately, there are several things you can easily do during the installation process to prevent leaks.  Read on to learn exactly what these things are. 

Use CPVC and Slip Nuts

If your new bathtub is slightly larger or wider, or a completely different shape than your old one, then the drainage lines probably will not match up exactly. This means that you need to attach a new PVC, CPVC, or steel piece of plumbing to connect the drain to the existing drainage lines.  To make sure that the drains themselves do not form holes or breaks, consider using CPVC materials.  CPVC piping is very similar to PVC.  Both types of pipes are made out of the same basic polyvinyl chloride, bur CPVC is treated to contain more chlorine compounds.  This enhances the strength of the material so it can withstand higher temperatures and more substantial amounts of pressure.

CPVC is typically used for hot water applications, but professionals are now starting to use the materials for drainage lines and other uses due to its added strength.  CPVC pipes are typically a light gray color, while PVC is often white, so it is easy to find at your local hardware store.  If you choose to use the CPVC, make sure that the drainage lines come with slip nuts.  These nuts contain rubber o-rings or gaskets that create air airtight seals when they are twisted into place.

Consider Quick Connect Fittings

New water lines need to be secured underneath the hot and cold water faucets that connect to your bathtub.  Flexible stainless steel water lines are used to connect the faucets to the copper, PVC, or CPVC supply lines.  In most cases, threaded nuts sit at the end of the lines so they can be connected.  It can be difficult to hand tighten these nuts or to even get them tight enough using a wrench.  Some people may use plumber's tape or pipe dope to create tighter seals, but fittings may not loosen if lines or pipes need to be replaced in the future.

Using Quick Connections

Instead of using threaded connections, use flexible water lines with quick-connect or push-to-connect ends.  Quick connections are connectors that contain metal teeth, o-rings, and plastic sleeves.  The metal teeth grip the end of the pipe and the o-ring and sleeve creates the seal.  Before you use the quick connect, you need to make sure that the ends of the hot and cold water supply lines are smooth and free of any threaded pieces or old connections.  Use a pipe cutter tool to cut the pipe beneath the connection or tapered edge.

Once the end is cut smooth, look for a support collar attached to the quick connect.  This part of the fitting is a larger plastic piece that is not needed if you are connecting the flexible line to either copper or CPVC supply ends.  Remove it with a pair of needle-nose pliers.  Slip the connector over the cut pipe edge and press it in place while you twist the device a small amount.  You will hear a click when the metal teeth of the fitting is secured in place.

If you ever need to remove the connections to complete plumbing repairs, then purchase a release tool for this purpose.  You can also place even pressure around the plastic piece that protrudes from the connector.  This piece is a part of the quick-connect fitting that forces the teeth to release from the pipe.