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Question:

What is the function of a Vented Loop?

Answer:

A Vented Loop is an anti-siphon device. It is placed in the line above the water line and allows air in as the waste or water flows through the line. It is to prevent siphoning if your thru-hull or Seacock fails and your toilet or holding tank is below the water line.

Question:

When is a Vented Loop necessary?

Answer:

There are many factors that determine when a Vented Loop is necessary. These are just a few reasons you may need one.
Please consult an installer before deciding if you do or do not need a Vented Loop.

When your toilet is below the water line and you’re using raw water (meaning the supply water is being pulled to the toilet from the outside of the boat. E.g. lake water / sea water). You would also use a Vented Loop if your holding tank is below the water line and you do not have a discharge pump that would prevent backflow that could result in siphoning.

If your toilet or holding tank will be under the water line when you’re vessel is heeled over. (see diagram above)

Question:

Where do I install a Vented Loop if my toilet is below the water line?

Answer:

If your toilet is below water line you would install the Vented Loop in the line between the toilet pump and the bowl. It would NOT go in the intake line. The vented loop allows air into the line and your pump would not be able to pull water to the toilet because it would be pulling air in from the vent portion of the loop (not being able to create a suction for the water supply)

Question:

Where do I install the Vented Loop if my holding tank is below the water line?

Answer:

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.

Question:

How high does my Vented Loop need to be above the water line?

Answer:

You should not exceed more than 6-feet of lift in the line to the top of the Vented Loop. It is suggested to have the Vented Loop at least 8-inches above the highest water line.

Question:

Are there any discharge pumps that prevent backflow so I don’t have to install a Vented Loop if my holding tank is below water line?

Answer:

Discharge pumps with check valves in them can prevent backflow issues that cause siphoning. The SeaLand T-Pump (Transfer Pump) is our best seller for discharge pumps. Most manual pumps have check valves as well.

Please consult with an installer before deciding that your installation of a discharge pump will take the place of needing a vented loop.

Question:

Do I need to install a Vented Loop between my toilet and my holding tank for any reason?

Answer:

No.