Use and Care Manual

ASME A112.18.1-2018/CSA B125.1-18 Plumbing supply fittings
July 2018 © 2018 Canadian Standards Association
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5.9 Backflow prevention
5.9.1 General
Fittings shall be tested in accordance with the applicable tests specified in Clauses 5.9.2 and 5.9.3 and
then retested within 48 to 96 h of completing all applicable life cycle tests specified in Clause 5.6.
5.9.2 Fittings with plain outlets
5.9.2.1 Air gaps
Fittings with plain outlets shall be protected by an air gap in accordance with ASME A112.1.2 or
A112.1.3. For deck-mounted fittings, the air gap shall be measured as the vertical distance from the
plane of the mounting surface of the fitting to the lowest point of the outlet. Where the fittings
incorporate threads to accept an aerator or similar device, this measurement shall be taken with the
aerator or similar device installed (see Figure 1).
A critical level mark on the fittings may be used as an alternative to the air gap. The critical level shall be
confirmed by the test method specified in Clause 5.9.2.2.
5.9.2.2 Test procedure
5.9.2.2.1
The specimen shall be set up as follows:
a) Remove all checking members or open them fully.
b) Install the specimen as recommended by the manufacturer by mounting it over a container
measuring approximately 380 × 250 × 150 mm (15 × 10 × 6 in). Ensure that the mounting surface is
plumb or level with the water surface in the container.
c) Allow the outlet of the specimen to have a free area at least four times the area of its effective
opening between the container and the outlet.
5.9.2.2.2
The critical air gap test for fittings with plain outlets shall be conducted as follows:
a) Connect the inlet(s) of the specimen to a vacuum source.
b) Measure the vacuum at the inlet(s) of the specimen.
c) Provide a means to change the water level in the container, relative to the outlet of the specimen.
d) Start the test with the water level at the mounting surface level.
e) With the specimen fully open from the inlet(s) to the place of discharge to the atmosphere, apply a
vacuum of 85 kPa (12 psi) to the inlet(s).
f) Hold for 1 min. Back siphonage at this time shall be a cause for rejection.
g) Slowly bring the water level closer to the discharge outlet until the level at which back siphonage
occurs is reached.
h) At the level specified in Item g), measure and record the distance between the lowest point of the
outlet of the specimen and the water surface.
i) Return the specimen to atmospheric pressure.
j) Starting with the water level higher than where back siphonage occurred, apply a vacuum of
85 kPa (12 psi) to the inlet(s).
k) Slowly lower the water level until back siphonage ceases.
l) Maintain the vacuum for 1 min to ensure that water is not being drawn into the discharge outlet.