Is the Grevac anti vac trap a glassed bottomed trap where solids may be disposed off and also useful if valuables have mistakenly been thrown away?
The only thing I can think off regarding the puff pipe is was it a bellow for a plumber to check that flues had a sufficient flow? really confused
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How long have you been plumbing and what made you want to become a plumber ?
Don't worry about these questions too much, its more on how far I can go back in history
A Grevac trap was a patented form of anti siphon trap, it was a tubular form of trap, with a slight "jump up" on the tail of the trap, also there was a second pipe from the tail of the trap going to the bottom part of the inlet side of the trap, this pipe was above the trap proper, and the idea of the jump up was to break the water up so that it was not a solid plug and also at this turbulence where the other pipe joined would allow air to break the siphoning action in the trap by letting air back to the base of the trap
A puff pipe was a lead pipe taken off a lead basin waste, where the run would encourage self-siphoning, normally an inch or inch and a quarter, the end was turned over to form a roll, with either a cross wire or gauze fitted to the end which was built into an outside wall, close to the basin, to allow air into the waste, so that the water would not self siphon out of the trap
I started to cut my plumbing teeth by reading a Froy's 1938 catalogue, which was as thick as a bible if not more so, I wanted to become a Chef, but my old man wanted me to be in the building game, hopefully a chippy, so that we could go it alone, but wood and me dont mix
and I wanted to be something as faraway as possible, hence the plumbing, reckon that I've about 60 plus years of knowledge about plumbing somewhere in my head
It was for a small pipe, called a puff pipe, which connected the trap to the soil stack. They became obsolete about 50 years back after BRE research led to the adoption of the modern single pipe soil stack system. The old ventilated separate soil and waste stacks can still be seen on the backs of some old blocks.
a grevac was collated with the above in victorian properties circa 1860-1920
I think that you are thinking of the 1 pipe system = 2 pipes, the 2 pipe system = 4 pipes
Grevac traps were still being sold in the late '50's