PRIVATE WATER SYSTEMS - Piping - Types

Piping Types

The three types of pipes generally used in water systems are galvanized steel, copper, and plastic.

Galvanized Steel Pipe (1)Galvanized steel pipe is covered with a protective coating of zinc that greatly increases its life compared to black pipe. It is made in standard 21 foot lengths with each end threaded. The pipe is cut and threaded to fit the job. Joints are made by placing a small amount of pipe joint compound on the pipe threads and screwing on the fitting.

Galvanized steel pipe is suitable for all piping inside a building, but plastic and copper pipe are preferred for underground installation. Highly mineralized water greatly reduces the life of steel pipe.

Copper Pipe (1)Copper pipe is available in types "K", "L", and "M". Type K is heavy duty - pump suction lines and underground piping. Type L is standard weight - inside buildings, and type M is light-weight for use only behind walls inside buildings.

Both types K and L are available in hard- or soft-tempered form. Hard-tempered pipe is rigid and comes in 10 to 20 foot lengths. It is used for exposed piping inside buildings, where it can be fit closely to walls or ceilings. It needs very little mechanical support to keep it in position, compares to flexible tubing.

Soft-tempered tubing is excellent for underground use and for inside existing walls in old buildings.

Plastic Piping (1)Plastic pipe is available in flexible, semi-rigid, and rigid forms. Flexible pipe is common for underground water piping because of installation ease and economy. It is 1/2 inch or more in diameter and in coils of 100 feet or more.

Solvent welded, or glued, PVC semi-rigid pipe is now common as a result of better and more readily available quality, ditching equipment, and ease of joining. The joints of polyethylene pipe use nylon or brass fittings and stainless steel clamps and clamp screws.

Use only pipe fittings that have the National Sanitation Foundation seal, NSF. It assures that the pipe is safe for use with drinking water. There are five classes of plastic pipe and fittings that meet commercial standards established by the ASTM for potable household water:

1) Polyethylene (PE)
This flexible or semi-rigid pipe's strength decreases as the temperature rises, therefore it is for cold-water lines only. It has pressure ratings between 80 and 160 psi.

PE pipe is used for hot water heating in concrete floors; temperatures of up to 100 degrees F are common for foot comfort. For this use, however, the best brand of virgin plastic rated at 115 degrees F should be used. Also, mixing valves for water temperature control should be installed. Lines should also be laid in straight lines to avoid undue stress. PE pipe is available in diameters of up to 6 inches or larger; and it is joined by threads and clamps.

2) Polyvinyl Chloride (PVC)
This rigid pipe is available with pressure ratings of 50 to 315 psi. PVC should be used for cold-water only. It is used for some household cold water pipes and drains and in some permanent irrigation installations. Pipe for pressure water systems should be rated at least 80 psi. PVC comes in 20 or 10 foot lengths and common diameters; and it is joined with a coupling solvent. It is generally more resistant to crushing or puncturing than PE pipe, and it will stand slightly higher temperatures.
3) Acrylonitrile Butadene Styrene (ABS)
This semi-rigid pipe has pressure ratings between 80 and 160 psi,and is suitable for sewer pipe.
4) Chlorinated Polyvinyl Chloride (CPVC)
This material is similar to PVC, but it is better for handling corrosive water at temperatures 40 to 60 degrees F above the limits for other vinyl plastics. It is suitable for hot or cold water lines. Although this type of pipe was developed to handle hot water, the manufacturer's stress and temperature limitations should be checked before installing. Local plumbing codes should be consulted also.
5) Polybutylene (PB)
This pipe is suitable for both hot or cold water lines. Although this type of pipe was developed to handle hot water, the manufacturer's stress and temperature limitations should be checked before installing. Local plumbing codes should be consulted also.

In both of the classes - PB and CPVC- manufacturers sometimes make a number of pipes with different physical characteristics. Care should be taken in insuring the water system needs are met by the pipe selected.

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