Jean-David Beyer wrote:
Tim Daneliuk wrote:Regular check valves can allow leakage in the reverse direction (in theory, they don't, but most plumbing codes admit that they can and do). Where sanitary or health concerns apply, this cannot be tolerated. A backflow prevention valve is set up so in normal operation both check valves are open, or closed depending on whether the supply pressure exceeds the delivery pressure. But if the supply goes below the delivery pressure, both check valves are supposed to close. But even that is not enough. If either of those check valves leak, the vent is opened and any backflow that leaks through the supposedly closed check valve at the delivery end is vented to the floor or suitable drain and cannot return into the supply.On 5/3/2010 10:24 AM, Jean-David Beyer wrote:Tim Daneliuk wrote (in part):- If you end up doing some plumbing by tapping into the hot/cold mains another highly recommended things is to sweat in one-way valves when you do this.A regular check-valve is NOT the thing to use here, though. You will want an anti-backflow valve like this one: http://www.caleffi.com/caleffi/sl_SI/Site/Products/Catalogue/args/sezione/Family040_Non_controllable_reduced_pressure_zone_backflow_preventer_with_removable_filter/path/5~573~573_FIL-details/include/~applications~catalog~serie.jsp/index.sdoNot quite sure what you mean by a "regular check valve". The ones I installed are not as fancy as the one above, but they are one-way valves to prevent backflow. IIRC, they were about $10 US each.
If you want to see how one of these works, see this link: http://www.caleffi.com/en_IT/Technical_brochures/01008/01008.pdf -- .~. Jean-David Beyer Registered Linux User 85642. /V\ PGP-Key: 9A2FC99A Registered Machine 241939. /( )\ Shrewsbury, New Jersey http://counter.li.org ^^-^^ 10:25:01 up 34 days, 23:51, 3 users, load average: 4.45, 4.61, 4.65 ============================================================================================================= To unsubscribe from this list, go to www.freelists.org and logon to your account (the same e-mail address and password you set-up when you subscribed,) and unsubscribe from there.
