10 January 2002
penetrations. For a shallow trench system, the wall penetrations will typically be the same size as the inside
dimension of the shallow trench connecting to the valve manhole. For shallow trench dimensions, refer to
chapter 4 of this manual. Structural reinforcement must be designed around this opening. Drainage from the
trench will then flow into the manhole. For Pre-engineered or Prefabricated Underground Heat Distribution
Systems, sleeved openings will typically be provided with an expandable seal between the casing and the pipe
sleeve as indicated on figure 3-28. Structural reinforcement must be designed to avoid contact with the pipe
sleeve and water stop to prevent grounding of the system's cathodic protection.
(2) Waterproofing. Waterproof membranes will be placed in or below the concrete bottom slab
and continued up the outer sides to the top of the sidewalls in accordance with the valve manhole guide
(3) Pipe anchoring adjacent to valve manholes. Regardless of the buried distribution system, pipe
anchors should be provided between 2 to 5 feet of a manhole wall to minimize movement through the
manhole. For piping which passes through valve manholes, anchoring on one side only is typically adequate.
Anchoring piping on more than one side may restrict piping movement and overstress the piping in the valve
manhole. Anchors will typically be provided as part of the distribution system and will not be embedded in
the manhole wall. However, if the manhole is used to support an anchor, the manhole must be designed to
withstand the forces exerted by the system. Expansion compensation stress calculation will always be
conducted to ensure proper anchor locations throughout the distribution system. These calculations must
also account for the expansion in the valve manholes.
(4) Piping materials in valve manholes. Nonmetallic piping must not be used in the same valve
manholes as piping carrying higher temperature media that could cause the temperature around the
non-metallic piping to exceed the allowables and potentially cause permanent damage to the non-metallic
piping. In addition, chilled water systems with PVC carrier piping must never be installed in the same valve