Inverted P-trap with Vacuum Breaker
Inverted P-trap with Vacuum Breaker
(OP)
Hello.
I am working on an open loop cooling water system. The system has an open to atmosphere holding tank with pumps. On the return side just before the atmospheric holding tank I have an inverted P-trap and vacuum breaker to prevent the system from siphoning back when the system is turned off. The inverted P-trap is above the highest point in the system and the vacuum breaker is on top at the highest point of the P-trap.
I need help determining the set point of the vacuum breaker. I am using a Bell and Gosset #26.
ht tp://www.p exsupply.c om/Bell-Go ssett-1130 75-26-Vacu um-Breaker
Part Description:
Designed to protect closed vessels and piping systems against collapse when the induced vacuum exceeds design conditions. When used on steam heating systems, the No. 26 Vacuum Breaker controls induced vacuum, permitting normal return of condensate to the boiler. Adjustable range 1/4" to 20" (mercury) vacuum. Factory set to 4".
This is factory set to 4" mercury vacuum which is ~4.5ft water. How do I calculate the vacuum pressure due to the siphoning effect? I would think it would be a based on the down leg length of the P-trap, from the top of the P-trap to the atmospheric tank?
Right now when the system is turned off some water comes back in to the atmospheric tank (as expected from top of P-trap to tank). But then a small amount of water continues to bleed back into the system. I have verified that water is not coming back to the tank on the supply side. I am not sure if the vacuum breaker is set correctly or if it could be undersized. Any thoughts?
I am working on an open loop cooling water system. The system has an open to atmosphere holding tank with pumps. On the return side just before the atmospheric holding tank I have an inverted P-trap and vacuum breaker to prevent the system from siphoning back when the system is turned off. The inverted P-trap is above the highest point in the system and the vacuum breaker is on top at the highest point of the P-trap.
I need help determining the set point of the vacuum breaker. I am using a Bell and Gosset #26.
ht
Part Description:
Designed to protect closed vessels and piping systems against collapse when the induced vacuum exceeds design conditions. When used on steam heating systems, the No. 26 Vacuum Breaker controls induced vacuum, permitting normal return of condensate to the boiler. Adjustable range 1/4" to 20" (mercury) vacuum. Factory set to 4".
This is factory set to 4" mercury vacuum which is ~4.5ft water. How do I calculate the vacuum pressure due to the siphoning effect? I would think it would be a based on the down leg length of the P-trap, from the top of the P-trap to the atmospheric tank?
Right now when the system is turned off some water comes back in to the atmospheric tank (as expected from top of P-trap to tank). But then a small amount of water continues to bleed back into the system. I have verified that water is not coming back to the tank on the supply side. I am not sure if the vacuum breaker is set correctly or if it could be undersized. Any thoughts?





RE: Inverted P-trap with Vacuum Breaker
Katmar Software - Engineering & Risk Analysis Software
http://katmarsoftware.com
"An undefined problem has an infinite number of solutions"
RE: Inverted P-trap with Vacuum Breaker
Mike Halloran
Pembroke Pines, FL, USA
RE: Inverted P-trap with Vacuum Breaker
Mike, normally our standard designs do not allow for such standpipes (due to space restraints) so we incorporate vacuum breakers. If adjusting the vacuum breaker doesn't work we will give this a shot.
RE: Inverted P-trap with Vacuum Breaker
I would be tempted to quietly go and take the innards out of the vacuum breaker.
Katmar Software - Engineering & Risk Analysis Software
http://katmarsoftware.com
"An undefined problem has an infinite number of solutions"
RE: Inverted P-trap with Vacuum Breaker