Tip of the Week - Plumbing

Supply Plumbing

Plumbing System Overview
The plumbing system in a house consists of supply lines that bring water into the house, fixtures for using the supplied water, drain and waist piping for removing waist water, and vent piping for balancing the air pressure that builds up in the system. In this week’s Tip of the Week I cover supply piping. Fixtures, drain, waste and vent piping will be covered in a later edition.

Most supply piping cannot be seen in a finished house. The unfinished portions of a basement usually present the best opportunity to observe supply piping. Copper is the most prevalent material, although other materials such as galvanized steel, PVC plastic, cast iron and brass are sometimes used. Polybutylene – typically a grey plastic material - has been used in supply piping, but it is the subject of much controversy. In many installations it has been prone to leakage. It is important that the home inspection client is made aware of the problems associated with polybutylene piping.

Issues with Supply Piping
Common issues with supply piping include leaks, low water pressure and poor water quality.

* Leaks
Leaks can be caused by a number of reasons – age of the pipes, use of incompatible metals, or even the material itself. Brass, for example, tends to corrode faster than other metals and will eventually deteriorate resulting in leakage. When copper comes in contact with galvanized steel, it causes corrosion, with the galvanized steel corroding first. Similarly, copper in contact with iron or metal ducts causes the copper to corrode.

* Water Pressure
Water pressure can be either too high or too low. The optimal water pressure is between 50- and 60 psi (pounds per square inch). When water pressure is too low, in many cases a pressure tank or booster pump can be used to build the pressure back up. Often times, however, the problem is with the utility’s infrastructure and they may have to get involved to help resolve the issue. The absolute minimum plumbing standard for water pressure is 15psi, but this is really not a viable situation.

Water pressure can actually be too high. Water pressure above 80 psi needs to be reduced to levels approved by the local municipality. Excess water pressure can cause piping and fixtures to leak, sometimes going unnoticed until significant damage has been done. To reduce water pressure, a water pressure regulating valve can be installed to lower the pressure to within an acceptable range.

Shutoff Valves and Hose Bibs
As part of every home inspection, the main shut off valve needs to located and shown to the home inspection client. The main shut off valve cuts off all water supply to the house. Therefore, its location is important - particularly when plumbing repairs need to be made.

Hose bibs located outside of the home should only be operated when outdoor temperatures are conducive to do so. In colder temperatures the hose bib shut off valve (which is inside the house) should be closed in preparation for winter. The outdoor faucet should be opened to allow any excess water between the shut off valve and the hose bib to drain to the outside. The pipe between the shut off valve and the hose bib faucet should have a downward slope so that water does not remain in the pipe where it can potentially freeze during winter and cause the pipes to crack.

Cross Connection
There are many things we expect from our plumbing systems – good water pressure, no leaks, and clean water in the supply system. A situation where clean water can become contaminated is known as a cross connection. For example, a cross connection can occur if a faucet is below the flood rim of a sink. That is, when a sink is filled to its rim and the faucet opening is below the water, dirty sink water can be siphoned back into the faucet in the event of negative suction which does occur on occasion in supply plumbing.

Here are a few examples of where dirty water can be siphoned back into the supply plumbing:
* When a sprayer or removable shower head is laid on the bottom of a sink or bathtub allowing dirty water to go back into the fixture
* A toilet where the supply water enters the bowl from the bottom\
* A dishwasher that doesn’t have a stopgap device for properly removing dirty water
* A washing machine that discharges dirty water into a laundry tub where the faucet is below the flood rim.

Other Supply Piping issues
* Incorrect support
To work as designed, supply piping needs to be supported properly. A good practice is to have vertical piping supported at every floor. Horizontally, copper piping should be supported every 10 feet and plastic piping should be supported every 4 feet.

* Water Hammer
You have no doubt at one time or another turned off a faucet and heard a loud banging sound. This is known as “water hammer”and it is cause by a lack of space for the water to travel to when the faucet is turned on and off. Supply piping needs excess piping to accommodate the air pressure that builds up in the system. Without the excess piping, considerable pressure builds up in the system which causes the banging sound when the water is turned on and off.

… and this is your Marquís Home Inspections Tip of the Week.

Derrek Hicks
Marquís Home Inspections
PO Box 2699
Germantown, Maryland 20874
240-401-1418 ph
derrekhicks@marquishomeinspections.com
http://www.marquishomeinspections.com/