Distribution piping

Water is supplied to the various fixtures throughout the house by distribution piping. The distribution system begins by the inlet supply pipe just after the water meter and consists of two components: supply mains and fixture risers. The supply mains are usually suspended from the basement ceiling and can be readily inspected in an unfinished basement. The fixture risers run between the supply mains and the fixtures and are usually concealed behind the walls. For the most part, the risers cannot be inspected.

In addition to copper, brass, and galvanized iron pipes, many communities also allow the use of plastic pipes for both hot- and cold-water distribution. Some communities, however, will allow plastic pipe only for use in cold-water lines. Trace and inspect all of the exposed water pipes in the basement. You will find that there will be a branch takeoff pipe that leads to the domestic water heater, and if the house is heated by steam or hot water, there will be a cold or hot takeoff leading to the boiler. As a point of interest, over the years, cold-water copper and brass pipes take on a darker color than the hot-water pipes. Sometimes you might find sections of cold piping “sweating” profusely. This is not a problem condition. It is merely condensation and can easily be eliminated by insulating the pipes or reducing the amount of moisture in the air with a dehumidifier.

Faulty plumbing does not necessarily mean that there is a steady stream of water leaking from a pipe or fitting, although if that is the case, immediate correction is necessary. Of particular concern are indications of aging and deterioration. Look specifically for signs of past and current leakage around fittings and valves. Look for mineral deposits, corrosion, and patched sections. The presence of galvanized iron pipes and fittings in a copper and brass plumbing system is a potential problem, as discussed previously. If you see iron pipes, you should make an estimate of the amount and anticipate their replacement. Copper pipes often take on a greenish cast, particularly around the fittings. Although this condition looks as if it could have been caused by water leaking from the joint, it is not. It is usually caused by the soldering flux. A leak, on the other hand, usually shows up as an encrustation of mineral deposits around the joint.

Brass pipes found in residential structures will usually be “red brass” or “yellow brass.” You can often tell the difference by the color. Red brass, however, is not really red but a yellowish brown. Yellow-brass water pipes are more vulnerable to corrosion and dezincification (zinc leaching out of the brass into the water) than red-brass pipes. The projected life for yellow-brass pipes is about forty years; seventy-five years for red brass is not uncommon. The weakest part of a brass pipe is the threaded joint. With some older yellow-brass pipes, the threads are paper thin. If force is applied to one of the pipes (with a wrench during a repair or even by leaning on the pipe), the joint could easily rupture. Usually weak joints can be detected by a slight encrustation of mineral deposits. If you find encrusted joints on brass pipes, you should anticipate repair or replacement of those sections.

When the distribution pipes are brass, look along the length of the pipes for signs of leaks. Brass pipes are vulnerable to pinhole leaks along their length. Depending on its chemical quality, the water in the pipes can cause some of the zinc in the brass to dissolve. When this occurs, pinhole openings can be seen along the length of the pipe. Because of the small size of the openings, water drips from the holes very slowly. In many instances, the water will evaporate before it drips, leaving whitish mineral deposits around the opening. (See FIG. 13-9.) Eventually the deposits can self-seal the leak, although the pinhole openings will get larger.

I once inspected a house that had this problem. The owners had moved out in the beginning of the winter before they found a buyer. As a precautionary measure, water was drained from all of the pipes to keep them from freezing over the winter. My inspection took place the following spring when the water was turned on. The sudden surge of pressure in the pipes was enough to loosen all of the deposits, and water started to leak out all along the pipes so that it looked like a sprinkler system. If you see brass pipes with mineral encrustations along their length, even though there might not be any current leakage, those pipes should be replaced.

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Barry replied the topic: #12299
That's a scary story about pipes being left empty in the winter and then the joints all leaking in the spring when the water is turned back on.