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urine can't siphon
Thursday, May 24 2007
Naturally I'd used water to test the first urinal unit in the nascent household "urine plumbing network" I've been building, but I'd poured it in much more quickly than anyone ever produces urine. This had an unexpected but thoroughly-predictable effect; as the water drained from the system, it siphoned the water out of the trap, leaving the entire system dry. If I wanted a permanent layer of oil to keep urinous odors from coming up the pipe, I'd have to have some mechanism to allow air to enter the top of the system. In a normal household drainage system, one that ends up at a sewer or septic field, there are usually vent stacks that reach up through the roof to gather any air that the plumbing needs for drainage. But I know from the experience of living in my childhood house that such vent stacks aren't always included in household plumbing, particularly in houses that originally depended on outhouses (as my childhood house had, several owners before my parents bought it in 1976). In lieu of such a stack, under the bathroom sink was a simple check valve that allowed air into the drain while forbidding it from flowing the other way. This system didn't work very well, though, because it seemed the bathtub's trap was often pulled dry by toilet flushes, allowing foul sewer gas into the bathroom.
My urinal system would have very modest flow rates and it seemed doubtful that the process of a flushless urination could set up a siphoning action capable of draining the trap, particularly in the 3/4 inch PVC I was using. But to play it safe, I decided to add a PVC check valve to the top of the system, just behind the urinal unit I was assembling for the laboratory.
Today Gretchen began a mini-residency at Blue Mountain Center in the Adirondacks, the same place she'd spent an entire month a little less than a year ago. This particular residency would only be for five days; she'd won it in a lottery after another group that had been scheduled for Blue Mountain flaked out. This left me alone with the critters and the tender mercies of my bachelor dietary philosophy, which has a whole food group reserved for malt liquor. The Hurley Avenue Citgo stopped carrying forties since the last time I went there to buy them, so I'd been forced to buy two 24 oz cans of Olde English.
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