Spill-Resistant
Vacuum Breaker.
A PVB with a spring-loaded check that prevents the start-up dribble. Specified anywhere a PVB's discharge would be a nuisance — janitor closets, laboratory benches, café back-of-house. Same protection class as the PVB; better behavior on commissioning.
What it fixes
A standard PVB will discharge a small amount of water — roughly a teacup — every time supply pressure rises through about 5 psi during normal start-up. Outside, that's fine; it dribbles into a planting bed. Inside, in a janitor's closet or on a laboratory bench, that's a daily mop. The Spill-Resistant Vacuum Breaker adds a spring-loaded second check that holds back the spillage until full operating pressure is reached, then opens normally. The protection class is identical to the PVB (back-siphonage only, no back-pressure), but the day-to-day behavior is suited to indoor mounting.1
Construction
An SVB body looks essentially like a PVB with a slightly taller hat — the air-inlet poppet is positioned above a small additional check that seals during pressurization. Two test cocks, two shutoffs. Most SVBs in Milwaukee are 1/2″ or 3/4″ and serve a single fixture (a janitor sink with a chemical-dosed hose, a laboratory water bath, a darkroom developer wash).
When an SVB is right
- Janitor closet
A mop sink with a hose dosed for floor chemicals. The single most common SVB application in commercial buildings.
- Laboratory water bench
A faucet over a beaker rinse station with a vacuum-aspirator below.
- Photographic darkroom (still found)
Developer-rinse line. Less common than it was, still present in two Milwaukee photo cooperatives.
- Indoor commercial laundry
Soap-injection isolation at a single washer bank.
- Beverage-mixing bar back-of-house
A faucet with a non-carbonated soda gun.
Test sequence
The test is the same as a PVB — verify air-inlet opens at the right differential, verify the check holds — with the additional verification that the spill-resistant secondary check seals during start-up. We do this by closing SOV-2, opening SOV-1, watching for any discharge from the air-inlet during the pressurization. A drop is a fail.
USC FCCCHR-approved SVB models we stock
| Mfr / Model | Sizes | USC list # |
|---|---|---|
| Watts 008 / 008QT | 1/2″ – 2″ | 56-009 |
| Febco 765SR | 1/2″ – 2″ | 56-014 |
| Apollo 4SG-200SR | 3/4″ – 2″ | 56-022 |
| Wilkins 720ASR | 3/4″ – 1.5″ | 56-017 |
References
- ASSE 1056. asse-plumbing.org
- USC FCCCHR §56 listings. usc.edu/dept/fccchr
- Watts 008 product page. watts.com
- Febco 765SR spec. wattscanada.ca
- SPS 382.41(11). docs.legis.wisconsin.gov