Public restroom water pressure woes

The park's director of public works called with a water-pressure issue: We have a new restroom facility and the water pressure can't be regulated properly help! He asked if I'd be willing to meet with the architects, engineers, plumbing contractor, and a water company official. Since everyone loves a good mystery, I decided to oblige. I had tested their below-grade, confined-space-entry twinned backflow

The park's director of public works called with a water-pressure issue: “We have a new restroom facility and the water pressure can't be regulated properly — help!” He asked if I'd be willing to meet with the architects, engineers, plumbing contractor, and a water company official. Since everyone loves a good mystery, I decided to oblige. I had tested their below-grade, confined-space-entry twinned backflow preventers for years, and our records indicated that just 30 psi was available, which was not very surprising, given that this park is located on top of one of the highest hills in the area.

The new restrooms were spotless and secured from public access. Portable toilets were being utilized to accommodate the park's visitors. The plumber's work was immaculate with distribution piping sized exactly as the engineers had specified for the water closet and urinal flush valves (the old bathrooms had utilized tank-style water closets and urinal flush valves that didn't need higher pressure). Squatting in the center of the mechanical space, was a dual-booster pump rig with an alternator to give each of the multi-horsepower on/off pumps equal run time. An 80-gal. ASME expansion tank was connected to give the booster pumps adequate run-time.

The director must have read my mind: “The engineers specified this booster pump package.” He flipped the switch and the booster pumps began their on/off rapid cycling dance of self-destruction! The cycling was caused by the minimum pressure cut-off switch, which required no less than 20 psi to prevent cavitation, which would have eroded the impellers rapidly, not to mention huge power consumption from short-cycling.

The engineers and architect had elected not to attend our meeting. My pressure gauge indicated that the building's after-the-backflow pressure was 24 psi. This was not a surprise to me, given the change in elevation from the below-grade meter vault and pressure reduction caused by passing through two double-check backflow preventers.

The water company official announced that the incoming water line pressure was 60 psi, and said, “Must be something wrong with the backflow preventers in the meter vault … Let's move to the pit and have you hook up your pressure gauge.”

The pit is borderline confined space, and I didn't have my four-gas tester, harness or tripod gear, plus, I would need a top-side trained technician for safety and compliance. Accordingly, we call this pit “the widow maker” and every time we've tested this pit, it registers zero for oxygen.

Truth be told, this pit is borderline confined-space entry because it's only 4-ft. deep, which places my head above grade to breathe open air, containing 21% oxygen, as long as I remain standing.

To connect the three hoses to either of the two backflow preventers, I removed the ports' brass caps (we had installed the brass adaptors years ago) and screwed on the high-pressure hoses that are attached to the pressure differential gauge. (Port No. 1 is upstream of the first check, and our PSID rig incorporates a pressure gauge.)

In order to accomplish such a task, it was necessary to squeeze through the manhole opening and kneel, or squat, in the pit with my head well below grade, breathing air that would have had absolutely no oxygen. There's no warning without testing — in one second you're here, and in the next nano-second you're out like someone flipped a light switch. Death under these circumstances is quick and often comes in pairs because the top-side observer often attempts an ill-fated rescue. I made arrangements to return the next morning.

Exiting along the park's half-mile access road, I noticed a large water tank that was difficult to see through the forested woodland. Pulling off the road, I found it to be constructed with seven 9-ft. high welded rings of steel. That grants a 63-ft. elevation, and there is a dome that caps off this tank, which would add about 5- to 10-ft. of additional elevation if the tank were filled to its atmospheric vented overflow. The tank appeared to be a few feet higher in elevation than the water-meter vault. One pound of pressure is generated by every 2.31-ft. of elevation in any column of water (the diameter of the water column has no affect on the psi at its base).

When we checked the inlet pressure in the meter vault the following morning (after testing, ventilating the pit and harnessing to our tripod), we found the static pressure to be 30 psi — in advance of the twinned backflow preventers first check, which would indicate the water level was 69.3-ft. above our gauge. There was no way that the Binford-2000 booster pump package could be utilized. Besides there were plans to demolish two restrooms located more than three quarters of a mile away and install new restrooms with the same flush valves utilized in this new non-functioning restroom facility.

A quarter-million dollars worth of new restrooms stood idle! A 4-in. diameter, three-quarter mile long PVC schedule 80 water line with new restrooms at either end would need no less than 40 psi delivery pressure at the flush valves. The heat was on to get this resolved — a much better solution was available, but getting it approved was the challenge. Tune in next month for the resolution.

Dave Yates owns F.W. Behler, a contracting company in York, Pa. He can be reached by phone at 717/843-4920 or by e-mail at Dave.Yates@fwbehler.com.

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