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Jan
Depends on the length of the discharge hose and whether there is a vented loop and whether the discharge is below the waterline at the time the pump shuts off. Bilge Pump Out Line Type 20913 Vented Loops include a sensitive marine vacuum breaker with a stainless steel spring to hold the poppet closed.
What I did was disconnect the bilge pump and shower pump hose at the waterline thru-hull mount a vented loop as high as the hose would reach on the bulkhead aft the head connect that hose to one side of the loop and add a length of hose from the other side of the loop to the thru-hull.
Vented loop for bilge pump. Standard H-22872 dated 798 requiring a vented loop on the bilge pump outlet hose. All vented loops are designed to have fluids pushed through them. If you try to pull through a vented loop you will pull air into the line and not move the heavier fluid.
Be sure the pump is on the correct side of the vented loop. Low-maintenance using a vented loop allows you to not use valves which require frequent maintenance in your bilge-pump discharge line. High-flow using a direct discharge method with preferably 2 valves in the discharge line allows you to run your bilge-pump discharge out a through-hole that is at or below the water line.
May 2 2014. I have a siphoning question about the bilge pump vented loops. I recently installed a second automatic bilge pump slightly higher than the original in my 1970 E32.
I put the outlet near the top of the transom on the port side because there was already a hole there. I have a vented loop installed very close to this outlet with a. The vast majority of the times the bilge pump works it is for small nuisance amounts of water.
I installed a smaller bilge pump with a vented loop up near the galley sink and a small diameter hose. The back-flow is maybe a cup. Much better all around.
Heres some more details. Im a fan of the Forespar vented loops and I use one for each of my bilge pump outlets. Theyre not too pricy and the peace of mind is well worth it.
What I did was disconnect the bilge pump and shower pump hose at the waterline thru-hull mount a vented loop as high as the hose would reach on the bulkhead aft the head connect that hose to one side of the loop and add a length of hose from the other side of the loop to the thru-hull. Also remember that if there is enough of a rise in the hose above the pump as there may be for example with a vented loop water will flow back down and out of the hose into the bilge when the pump stops because of its automatic switch. If enough water flows back it may activate the switch again and cause the pump to cycle.
A major oversight was that the large electric centrifugal bilge pump did not have a vented loop to prevent back syphoning. The previous owner had installed a non-return valve to stop water flowing back in to the bilge a definite no-no for this type of pump. Bilge pumps should discharge above the waterline but those that do not require a siphon break.
A vented loop is acceptable per ABYC. Standards but a check valve is not. A check valve can only be used to prevent cycling of the pump but configuring the pump and float to eliminate the cycling is.
If your holding tank is below the water line you would install a Vented Loop between the discharge pump and the seacock. That way the pump is pushing the waste past the loop. If the Loop is installed before the discharge pump it would not be able to create a suction to transfer the waste because it would be sucking air in through the vent portion of the loop.
The pump in the bilge should be located as close to being vertically in line with the discharge hole as is feasible so that the length of horizontal run is minimised. The maximum lift height will be determined by the distance between the pump outlet and the discharge point or the top of any loop vented or otherwise in the line. Most bilge pumps are centrifugal and do not have enough power to push past the backpressure on the checkvalve.
The proper solution is to install a vented loop as close to the pump as possible. He top of the loop must be above the highest point of the hose run. Vented Loop Stops Back Siphonage Always Test Before Installing Bilge Pump Out Line Head Flushing Water and Discharge Lines Engine Wet Exhaust Line Type 890-913 Vented Loops include a sensitive marine vacuum breaker with a stainless steel spring to hold the poppet closed.
A vacuum will pull the poppet open permitting air to go into the system. Marine Vented Loops Parts. Plumbing systems below the waterline need to consider adding a marine vented loop to prevent the back siphoning of sea water.
Vented loops also referred to as anti-siphon valves prevent the siphoning of water by allowing air to enter when the line is not in use and sealing as water or other fluids pass by. 38mm 15 air valve loop to prevent back siphoning for waste water systems. Electronic Automatic Bilge Pump Low 1100GPH 12V.
Electronic Automatic Bilge Pump Low 750GPH 12V. Automatic Bilge Pump 500 GPH 12V. Bilge Float Switch 122430V.
Vented Loop - Suits 38mm - 1 12 Hose - Prevents Seawater Siphoning Back When Installation is Below or Near Sea Level 139096 Online Price. 2800 Including 10 GST Tax. Bilge Pump Out Line Type 20913 Vented Loops include a sensitive marine vacuum breaker with a stainless steel spring to hold the poppet closed.
A vacuum will pull the poppet open permitting air to go into the system. The Vacuum Breaker is normally closed. It does not require the pressure of the system to close the breaker poppet valve.
Bilge pump check valve midship discharge just above water line. No vented loop and cant get high enough to put one above the heeled water line. But solutions arent easy and over the last 22 years with 2 Atlantic crossings it hasnt sunk the boat yet.
Depends on the length of the discharge hose and whether there is a vented loop and whether the discharge is below the waterline at the time the pump shuts off. Best case the volume of the hose between the vented loop and pump outlet will all flow back into the bilge at pump shut down centrifugal pump no check valve. A smaller ID hose would have less water coming back but also less flow.
I added a vented loop in the cockpit locker of our Catalina 30. Only the water in the hose from pump to the vent would return to the bilge. Too bad you couldnt have a shop vac on your float switch that would suck the water out and then empty overboard.
The lazarette sounds good keeps pipework out of her way but is a vented loop necessary. Wouldnt non-return valves suffice. November 30 2020 at 0813 Reply.
This comment is years later but I am posting it to recommend using a loop with anti-syphon vent for electric pumps. Relying on a single non return would worry me. The bilge pump goes to a 5 hose then to a check valve then to a loop well above water level then back down below waterline to a non-closable through-hull.
On the top of the loop there is a 14 hose that leads right back to our bilge below waterline. The water is coming through the vent hose that leads back to our bilge. What is a vented loop.
The discharge from a bilge can be mounted below the heeled or waterline only if a vented loop is installed to prevent water from siphoning back through the pump flooding the vessel. Proper installation of the vented loop is critical to preventing siphoning.