||New Standard Specifies Syphonic Roof-Drainage Systems
How should rain water be syphoned from the roof of a stadium-sized
warehouse? ASTM Standard F 2021, Specification for Design and Installation of Plastic Syphonic
Roof Drainage Systems covers syphonic drainage of large industrial
or commercial structures with a single roof. With a higher flow
capacity, syphonic drainage has advantages over conventional systems.
It uses fewer roof drains or outlets, and eliminates numerous
downspouts that carry rainwater to the ground level storm sewer,
according to Paul Sample, Ph.D., a plastics and piping consultant
who is president of Samples, Inc., Wilmington, Del.
Approved in June by ASTM Committee F17 on Plastic Piping Systems, Standard F 2021 will address key issues,
says Sample, the acting vice-chairman of ASTM Subcommittee F17.63
on DWV (drain, waste and vent). This standard provides performance
criteria necessary to accomplish functional roof draining with
safety and cost considered, explains Sample, who led the task
group that developed the specification. It establishes a protocol
for employing a well known principle (vacuum) to a potentially
troublesome construction feature, that of roof drainage. This
standard will set the pattern of expected performance for any
manufacturer or installer of roof drain system.
In a March 2000 article in PE Engineer magazine, Arthur Scott,
Ph.D., a professor in the Department of Building Engineering and
Surveying, Heriot-Watt University, Scotland, notes a few installation
and design concerns of syphonic drainage: Siphonic roof drainage
represents a significant advance in technology when compared to
conventional systems, he writes. Siphonic roof drainage can
result in savings in both cost and time during the construction
phase. However, ...there are still uncertainties regarding just
how these systems operateparticularly during priming. This lack
of understanding of system operation means that if a system fails,
it is often difficult to appreciate why the failure has occurred.
Furthermore, as siphonic system design necessitates a higher level
of expertise than is required for conventional systems, the performance
of these systems can be more reactive to small inaccuracies and
erroneous assumptions. To resolve this, over the past five years
there has been an increasing amount of independent research underway
attempting to understand how siphonic systems actually perform.
This includes the research of ASTMs task group of construction-product
manufacturers, DWV consultants, resin suppliers, and those experienced
in DWV product installation and performance who describe requirements
of necessary syphonic drainage components and system performance
criteria in ASTM F 2021.
This standard was developed to describe a previously unaddressed
means (syphoning) for efficiently removing rain water from nominally
flat-roofed buildings, concludes Sample. Syphoning is a well
known principle used for the natural movement of fluids through
a tube or pipe by employing negative pressure or vacuum. This
standard presents the necessary design requirements for functional
performance of such a system and cites the limitations. Properly
designed and installed, a syphonic drainage system will operate
more efficiently, be self-cleaning and require less piping than
gravity drainage systems.
Technical questions may be directed to Paul Sample, Ph.D., Samples, Inc., 308 Walden Rd., Wilmington, DE 19803-2424
(302/656-3212). Committee F17 meets Nov. 13-16 in Orlando, Fla.
For meeting or membership information, contact manager Pat Picariello, ASTM (610/832-9720). //
Copyright 2000, ASTM