Plumbing, Septics, Wells

Water pressure and flow

The water pressure in a house is an item of concern to most home buyers, and rightly so. However, water pressure per se is not usually the problem. If you see water trickling out of a faucet, it does not necessarily mean that the pressure is low. It means that the water flow is low. Low water flow can be caused by low pressure. However, more often than not, low flow is caused by a constriction in the supply pipes. The constriction can be the result of mineral or corrosive deposits on the inside diameter of the pipes, a kink in the pipe, or small-diameter piping. Quite often low flow at a fixture is caused by a partially clogged faucet aerator, which requires only cleaning. Water flow is measured in gallons per minute, and a sink faucet should be able to deliver 4 to 5 gallons per minute.

The water pressure available to a house at the meter varies, but it is usually in a range of 20 to 60 pounds per square inch (psi). I inspected a house that had a pressure gauge on the house side of the water meter. (A pressure gauge in the plumbing system is desirable but is not very common.) The gauge indicated that the available water pressure was 110 psi. Yet when three faucets were turned on at the same time, the water flow from each faucet was just a trickle. Regardless of how high the pressure is, if a constriction in the water pipes limits the water flow, the amount of water discharging from the faucet will be noticeably low. In this case, the pipes were made of galvanized iron. Over the years, corrosion and deposits had coated the inside of the distribution piping to a point where the pipes required replacement.

When you inspect the bathroom, check the water flow by simultaneously turning on the faucets in the sink and tub and flushing the bowl. There will usually be a drop in flow when the second faucet is turned on. If it is not very noticeable, do not worry about it-it is normal. You can trust your eye. If the water flow from the faucets looks good, then for all practical purposes, it is good. If the flow is noticeably low, record it on your worksheet. The condition requires correction. If there is a shower in the tub, check the operation of the shower diverter valve. When the shower is on, there should be very little or no water leaking out of the tub spout. If there is, the diverter valve is defective and will require replacement. Record this on your worksheet.

Check the flow for both the hot water and the cold water, but not at the same time. It is possible for the cold-water flow to be good and the hot-water flow fair or poor. Occasionally, when the domestic hot water is generated through the heating system, deposits form in the tankless coil, restricting the flow. If the hot-water flow is poor, you probably need to replace the tankless coil. (See chapter 16.)

Open and close the faucets rapidly. Do you hear a hammering and vibrating noise? You should not, but if you do, you are hearing water hammer, which occurs when the water flowing in the pipe comes to an abrupt stop. It introduces hydraulic shock and vibrations that can in extreme cases damage the pipe or fittings. The condition can be corrected easily by installing an air chamber or antiknock coil. These units provide a cushion of air to absorb the shock when the water flow stops.

Fig. 10-6. Sink traps: A-Properly vented P-type trap; B-S-type trap, usually not properly vented.

"P" Trap

While you are checking the water flow, look for water leakage around the faucets, and the drainage trap below the sink. If you notice that a portion of the trap is taped over, it is usually a makeshift correction for a leak. The drainage trap is not installed below the sink to catch rings or other valuables that fall down the drain, although very often this happens. The purpose of the trap is to provide a water seal that blocks noxious gases from seeping back into the room. If a sink trap is not properly vented, it can lose its seal from a siphoning action when the water is draining. (See FIG. 10-6.)

Usually the P-type sink trap is vented properly. However, the S-type trap is often not vented properly. You can tell by making the following test, although it is not foolproof. Fill the sink until the water is almost at the rim; then let the water drain. When most of the water has drained, if you hear a sucking and gurgling noise, the trap is not vented, and the water seal has been lost. When all the water has drained, if you let the water run freely for about five seconds, you will reestablish the water seal. If the main plumbing waste line has a house trap, the problem is minimized.

Check the drainage in the sink, tub, and bowl. Wrinkle up some toilet paper into a ball and throw it into the bowl. When the bowl is flushed, the paper should be carried down the drain. If the water in the bowl starts to rise to the top and then settles down without flushing, there is a blockage in the drain line that must be checked further and corrected. If the house has a septic system, this condition might indicate a problem with the septic system. If the water in the sink and tub does not readily drain away or drains sluggishly, there is a blockage in those drains that must also be corrected. In this case, the correction might be as simple as removing hair that has accumulated around the pop-up drain plug.

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