Groundwork

Water service lines are typically copper, polyethylene, or rigid plastic. Care should be taken to avoid damage when laying pipe:

  • Bury all water service lines below frost-depth.
  • Clear trenches of sharp rocks.
  • Provide continuous support (layer of soft dirt or sand) to prevent pipe from sagging or breaking when backfilled.
  • Bed PVC water lines in 4 in. of sand or fine dirt.
  • Keep the number of joints in trench to a minimum.
  • Backfill around pipe with fines until the pipe is submerged 6 in.
  • Do not backfill with heavy rock or cinder material that may promote corrosion. 

Water service lines may not be laid in the same trench as sewer lines unless they are separated by an elevation of at least 12 in. (some codes permit 10 in.). This means the sewer line will end up at least one foot below frostline. More typically, sewer and water lines are laid at the same depth in separate trenches spaced at least 5 ft. apart (Water Service Installation, below).

Install caution tape: Best practice calls for burying caution tape 12 in. below grade to alert future excavators to the presence of sewer and water service lines. This marking usually is color-coded — blue for water and green for sewer.

For information on subslab layout, see Structural Slabs.

Water service entry. Supply piping passing under a footing must have a clearance of at least 2 in. (See Figure: Drain Lines Near Footing in Groundwork).

Any supply piping passing through a foundation or footing must be sleeved with a pipe two sizes larger than the water line, allowing 1/2-in. clearance around the circumference of the supply line. This provides corrosion protection and prevents the water line from breaking if the foundation settles. Seal the sleeve with flexible foam to keep out the cold. In termite-prone regions, seal the outside with a flexible electrometric compound.

Lawn sprinkler systems that tap off a water service line must be protected by an approved backflow preventer (typically an atmospheric-type anti-siphon vacuum breaker). An atmospheric vacuum breaker must be at least 12” higher than the highest head in the system. If water pressure fails, this backflow prevention device will bleed air into the system rather than suck irrigation water back into the supply line. 

Turn the sprinkler run to rise 6 in. above grade after branching from the water service, and install a control valve. The backflow preventer must be located on the discharge side of the sprinkler control valve.

Figure: Water Service Installation
The bottom of water service lines must be at least 12 in. above sewer lines in the same trench (top) or in separate trenches spaced 5 ft. from sewer lines, septic tanks, or drain fields (bottom). Check local code for specific separation distances.
The bottom of water service lines must be at least 12 in. above sewer lines in the same trench (top) or in separate trenches spaced 5 ft. from sewer lines, septic tanks, or drain fields (bottom). Check local code for specific separation distances.

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