vertical down bends into gravity thrust blocks.
3.2.8
Commercial-Type Water Hammer Arresters
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NOTE: Designer will indicate location, quantity and
size of commercial type water hammer arresters on
the drawings. Commercial type water hammer
arresters shall be sized and located in accordance
with PDI-WH 201. Piping serving equipment having
quick-closing valves shall have suitably sized
arresters. For pressure of 448 kPa (65 psi) or
less, commercial water hammer arresters may be
reduced by the designer in number and size, if the
system does not contain quick-acting valves. Water
pressure regulating or reducing valves may be
provided in lieu of commercial type water hammer
arresters, if local use has provided satisfactory
performance. When required, install arresters as
close as possible to quick-acting valves, ends of
long pipe runs, and near batteries of fixtures.
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Commercial-type water hammer arresters, conforming to PDI WH 201, shall be
provided on hot and cold water supplies and shall be located as generally
indicated, with precise location and sizing per PDI WH 201. Water hammer
arresters, where concealed, shall be accessible by means of access doors or
removable panels. Vertical capped pipe columns will not be permitted.
3.3
DISTILLED AND DE-IONIZED HIGH-PURITY WATER PIPING
Metallic piping shall be tin-lined with tin-lined valves, or Type 316
stainless steel. Pipe, fittings, and valves shall be thoroughly cleaned at
the factory and fitted with plastic caps or inserts to keep out dirt and
prevent thread damage. Tin-lined pipe shall be regular class brass pipe
conforming to ASTM B 43, lined with tin that conforms to ASTM B 339. Ends
of pipe shall be tin-beaded, and terminal threads shall be tin-designed to
make up with tin threads in the fittings or valves. Outer threads shall be
brass. Tin thickness shall be a minimum of 1.6 mm 1/16 inch for pipe
valves and fittings. Nonmetallic piping shall be polyvinylidene fluoride
(PVDF), acrylonitrile-butadiene-styrene (ABS), chlorinated polyvinyl
chloride (PVC), and cross-linked polyethylene (PEX). Nonmetallic pipe
shall be installed in accordance with manufacturer's instructions.
3.3.1
Fittings
Fittings for brass pipe shall be bronze cast type, designed especially for
tin lining. Fittings for polyvinyl chloride (PVC) shall be socket type.
Polyethylene fittings shall be butt-fusion or socket-fusion type. Fittings
for stainless steel pipe shall be Type 316 stainless steel.
3.3.2
Valves
Line or shut-off valves shall be of the diaphragm type, with a
polytetrafluoroethylene (PTFE) diaphragm. Valves installed in tin-lined
pipe shall be of bronze body and tin lined. Valves installed in
nonmetallic pipe shall be nonmetallic body. Valves installed on stainless
steel pipe shall be stainless steel.
SECTION 15405A
Page 82
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