To diagnose plumbing noises, it is important to determine first whether the unwanted sounds occur on the system’s inlet side-in other words, when water is turned on-or on the drain side. Noises on the inlet side have varied causes: excessive water pressure, worn valve and faucet parts, improperly connected pumps or other appliances, incorrectly placed pipe fasteners, and plumbing runs containing too many tight bends or other restrictions. Noises on the drain side usually stem from poor location or, as with some inlet side noise, a layout containing tight bends.
Common Plumbing Noises
Hissing noise that occurs when a faucet is opened slightly, generally signals excessive water pressure. Consult your local water company if you suspect this problem; it will be able to tell you the water pressure in your area and can install a pressure reducing valve on the incoming water supply pipe if necessary.
Water hammer can usually be cured by installing fittings called air chambers or shock absorbers in the plumbing to which the problem valves or faucets are connected. These devices allow the shock wave created by the halted flow of water to dissipate in the air they contain, which (unlike water) is compressible.
Older plumbing systems may have short vertical sections of capped pipe behind walls on faucet runs for the same purpose; these can eventually fill with water, reducing or destroying their effectiveness. The cure is to drain the water system completely by shutting off the main water supply valve and opening all faucets. Then open the main supply valve and close the faucets one at a time, starting with the faucet nearest the valve and ending with the one farthest away.
Chattering or Screeching
Pumps and appliances such as washing machines and dishwashers can transfer motor noise to pipes if they are improperly connected. Link such items to plumbing with plastic or rubber hoses-never rigid pipe-to isolate them.
Other Inlet Side Noises
Correcting plumbing runs that suffer from flow-restricting tight or numerous bends is a last resort that should be undertaken only after consulting a skilled plumbing contractor. Unfortunately, this situation is fairly common in older houses that may not have been built with indoor plumbing or that have seen several remodels, especially by amateurs.
On the drain side of plumbing, the chief goals are to eliminate surfaces that can be struck by falling or rushing water and to insulate pipes to contain unavoidable plumbing noises.
In new construction, bathtubs, shower stalls, toilets, and wallmounted sinks and basins should be set on or against resilient underlayments to reduce the transmission of sound through them. Water-saving toilets and faucets are less noisy than conventional models; install them instead of older types even if codes in your area still permit using older fixtures.
Drainpipes that do not run vertically to the basement or that branch into horizontal pipe runs supported at floor joists or other framing present particularly troublesome noise problems. Such pipes are large enough to radiate considerable vibration; they also carry significant amounts of water, which makes the situation worse. In new construction, specify cast-iron soil pipes (the large pipes that drain toilets) if you can afford them. Their massiveness contains much of the noise made by water passing through them. Also, avoid routing drainpipes in walls shared with bedrooms and rooms where people gather. Walls containing drainpipes should be soundproofed as was described earlier, using double panels of sound-insulating fiberboard and wallboard. Pipes themselves can be wrapped with special fiberglass insulation made for the purpose; such pipes have an impervious vinyl skin (sometimes containing lead). Results are not always satisfactory.