On Sun, 5 Mar 2006 13:45:05 -0000, "Doctor Drivel"
wrote:

|
|"Aidan" wrote in message
roups.com...
|
| Tony Williams wrote:
|
| BTW: My old plumbing book has a gruesome tale about
| a plumber who blocked a vent pipe with a cork, to try
| and reduce the amount of water lost during a drain
| down. The resultant vaccuum caused parts of the
| plumbing to collapse inwards. Blocking a vent pipe
| may not be good news.
|
| Good point sir! Probably the copper hot water storage cylinder, which
| will be crushed by atmospheric pressure if you were to drain it without
| relieving the vacuum (hose out bathroom window, no hot taps open).
|
|I have seen that happen a few times, evn being open vented and not blocked
|
| On unvented hot water storage cylinders
| the mandatory T&P relief valve
| also acts as a vacuum breaker valve
| (I think, goes off to get book to check).

Done that myself :-( Should have known better. :-(
--
Dave Fawthrop dave hyphenologist co uk
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