BOOSTERS, BACKFLOWS, AND LEGIONELLA SERIES
By Dennis Whitelaw, President, Towle Whitney LLC
Huge benefits with the new GEN-5:
- Mitigate legionellae/pathogen harbors
- Avoid “water service disruptions”
- Eliminate the hassles of backflow testing
- Save Installation costs (material & labor)
- Save space
- Specify single SKU
In the article 4 Ways to mitigate legionellae “harbors” in the mechanical room, we highlighted the unsafe environments that are produced inside over-sized plumbing equipment. In this article, we’ll offer a value-engineered-solution.
Mitigate Legionellae/Pathogen Harbors
The majority of legionellae prevention strategies embrace monitoring, sampling, and system design, which is great. But it’s very likely the outbreaks are caused by pathogens that are already “hiding” in our systems. Like a spy novel, they’re hidden in plain sight in “harbors”, right under our noses.
If we know the locations of potential “harbors”, it would stand to reason to design the “harbors” out of the equipment, which is exactly what we did with the new GEN-5. In accordance with the intent of ASHRAE 188, minimizing “harbors” mitigates legionella and other pathogens by eliminating unsafe plumbing, including: sediment build-up, scale, tepid/stagnant water, biofilm, no-flow /low-flow water velocities, and infrequently used piping.
The mitigating effort is three-fold:
1) Incorporate multiple 2” RPZ/backflow preventers into the booster design.
The water velocity through two 2” RPZ’s is faster than one 3” RPZ. Combine the faster velocity with the smaller 2” diameter waterway; the result will be a higher water turn-over and more scouring.
2) Alternate the lead booster pump every 24 hours (or 6,12,18), which will eliminate “infrequent use” of all piping and pumps.
3) “Crossover Bypass Manifold” causes the water to flow simultaneously through the multiple backflow preventers, ensuring constant water flow to either pump. When testing either backflow preventer, the design eliminates the requirement to shut down pumps, thus AVOIDING (1) water service disruption and (2) turning pump off & on.
Avoid a “water service disruption”
ASHRAE-188-2015 addresses monitoring and disinfection following “water supply interruptions”. This is a very subtle, but a very important topic, as maintaining water flow improves a building’s water quality.
- Example 1: In a facility with ONE backflow preventer, during the annual (semi-annual) testing, the water supply gets completely shut off for at least an hour or more. Good luck finding a contractor that actually disinfects the backflow preventer before putting back into service.
- Example 2: In a facility with TWO backflow preventers, each backflow preventer can be tested WITHOUT interrupting the facilities water service.
Eliminate the hassles of backflow testing
In addition to the “water service disruption” problems, testing backflow preventers requires shutting down the backflow preventer. If there’s only one backflow preventer, the whole building will need to be shut down, meaning:
- 24+ hour shut-down notification.
- Huge inconvenience for multi-family building tenants
- Loss of water to critical equipment (boilers/etc.)
- Re-chlorination of the water line (mentioned above)
- Possible extended shut-down for maintenance.
Save on Installation Costs
A survey of contractors resulted in a large range for installed costs, which was a result of differences in labor rates, local code, material costs, etc. But anyway you look at it, the GEN-5 is less expensive than a separate 3” backflow preventer and booster system. (see chart below). And if the building design calls for two 3” RPZ’s in parallel, the savings will be huge.
Ask any engineer or contractor, and the answer will be the same: mechanical rooms are shrinking. And the architects would like to shrink them even more, and use the space for more “revenue producing” space. Assume a 3” RPZ covers about 20SF of floorspace at $100 to 200SF in larger cities. A GEN-5 duplex is about 29” x 45”, which not only fits through a doorway, but saves $ 2,000+ in floor-space.
Everything gets simpler when the backflow preventers, fittings, piping, and booster are all combined into one model.
- The engineer spec’s a single SKU
- Backflow and boosters are tested as a single SKU.
- Contractor orders a single SKU, and only needs to connect:
- two water lines
- one DWV line
- two power lines.
In addition to the standard duplexes, triplexes and vertical pump systems will be available in the GEN-5 design.
Few equipment designs combine huge benefits and savings. To further discuss, please visit our website, or contact Dennis at firstname.lastname@example.org, or 800-807-9827.