If you have a built-in lawn sprinkler system, chances are you're familiar with plastic water pipe. What you may not realize is that in most places it is approved for use inside your home as well as outside. However, there are a few building departments around the country that don't allow the use of plastic water pipe inside the home. They consider the toxic fumes of burning plastic an added danger during a house fire. Some don't feel that it is safe to use plastic no matter how many access doors are built into a project. In any event, it is apparent that as the building community becomes more familiar with plastic-water-supply systems, we will see more and more plastic water lines being used in home construction.

Plastic sewer systems are virtually the only variety in existence. Residential cast iron sewers are being phased out. Plastic lines are smoother inside than iron and therefore capable of doing a superior job of transporting waste materials from the house to the street. Also, plastic is inexpensive, easy to install and does not rust. The only drawback to plastic sewer lines is that they are noisy. In upgrade installations clay wrapping effectively solves the sound problem.

The requirements for installation of plastic water pipe are far more stringent than those of non-pressurized sewer line; this because, when under pressure, plastic water pipe occasionally separates at its connections. Because of this occasional joint failure, access panels are required whenever plastic pipe is installed into inaccessible areas such as walls, sealed floors, sealed attics, etc.

With proper materials, a home can be safely equipped with plastic, and cost-effectively at that. But remember, not all plastic pipe is the same.

Some types can stand more pressure and some will withstand heat better than others. Keep in mind, there is a difference between the low-pressure pipe used between the valve and a sprinkler head in the garden and the kind of high pressure plastic pipe and fittings needed between a water heater and a shower valve.

Consider:
1) Does the building department allow the use of plastic water pipe?
2) Is the available plastic water pipe properly rated for use with the existing water pressure and temperature?
3) Are all joints going to be readily accessible after the project is complete?

If the answer to all these questions is yes, you can count on saving big bucks on your next plumbing job.

Working with plastic pipe is easy. First, measure and cut the pieces. Old carpenter's rule: Measure twice and cut once. With the measurement made, use a saw with a fine-tooth blade to make the cut. A hacksaw is good, but sanding or filing will be required to remove the resulting burrs. If you regularly work with plastic pipe, you might want to invest in a plastic pipe cutter. They cost about $10, and cut square and clean every time, without burrs.

Next you will want to assemble all the pieces without glue to see how everything fits. Alignment marks are made at this time. The marks help you gauge when the pipe is correctly seated and when it is at the correct angle in relation to other fittings. Once you have all the pieces properly cut, you've reached the cleaning and gluing stage. A blue colored chemical known as primer is used to clean the pipe and make it ready to accept the glue. As with the glue, the primer should be applied to both sides of every joint the outside of the pipe and the inside of the fitting. Once the primer has dried, the glue can be applied. You can't use too much glue; don't try to save money when applying it. Once the glue has been applied, you will have only a few seconds to properly "seat" the connection. This is where the alignment marks come in handy.

Once the pipe has seated, hold the elements together for about 10 seconds. This gives the glue a chance to dry. Letting go too soon could result in a bad bond. Plumber's tip: if the fitting seems loose during the first assembly (before gluing) try other fittings. Occasionally a fitting will not match the pipe size closely enough. These leak after everything has been glued. Wait for about half an hour before turning the water on. This gives the glue ample time to set up and will help reduce the chance of an exploding joint.