Plumbing a New Head System

DavidL · Post by **DavidL** » Sun Apr 01, 2007 9:02 pm

Finally getting around to installing a new head system. I have a few questions on installation of a Lavac head.

I am pumping the head into a holding tank and plan to have one discharge line to a Y-valve and then one hose to overboard discharge and the other to the deck pumpout. I'm using the Henderson pump to empty the tank. First question is do I need a vented loop installed on the overboard discharge line? Second question is where should I place the discharge pump, before or after the y-valve? If after, should it be before or after the high loop?

Thanks.

Post by **Tim** » Mon Apr 02, 2007 6:09 am

The discharge pump should go as close to the toilet as possible, which means before any y-valves or loops.

Your proposed setup is similar to what I have. I have a high loop for the discharge (after the pump), but did not install a siphon break since water cannot siphon back through the discharge pump.

DavidL · Post by **DavidL** » Mon Apr 02, 2007 8:17 am

Thanks Tim.

One possibly stupid follow-up question. Since the pump should be as close to the tank, is it possible to have the waste settle in the discharge line? I guess I'm really questioning the mechanics of the pumps. Once the tank is emptied and the pump is sucking air, will it still move the waste along downstream (after pump) and completly empty that line?

Figment · Post by **Figment** » Mon Apr 02, 2007 9:24 am

I'm confused, are you proposing a one pump system or a two pump (one to flush the head and another to empty the holding tank) system?

DavidL · Post by **DavidL** » Mon Apr 02, 2007 9:27 am

Two pumps, one for the head and the other for the holding tank.

Post by **Tim** » Mon Apr 02, 2007 10:37 am

Oh. I was confused too. My comments on the pump above are for the actual toilet discharge pump.

For the holding tank pump, though, the same basic principles apply. Install your y-valve after the pump so that you can use the pump to discharge both overboard and through the deck fitting if need be.

Your specific installation will determine the need for a vented loop in the overboard discharge line. But assuming that the various valves (seacock and y-valve) are closed except when you might actually be discharging the tank overboard via the pump, I don't see a call for a siphon break. I like to avoid them whenever possible since if they truly serve no purpose, why add the complexity and leak/seepage potential?

Some installation will virtually require one, though. It all depends.

Hirilondë · Post by **Hirilondë** » Mon Apr 02, 2007 6:09 pm

There is no need for a wye valve on the tank discharge side. A wye fitting will work just fine. If your pump is discharging then the cover on your deck pump out will seal off that leg from sucking air. If you are using the deck pump out then the discharge pump and/or the seacock will block off that leg.

If your tank is lower than the waterline ABYS wants you to have a vented loop to protect the tank. You won't be using a direct overboard option, hence your toilet only goes to the tank, and therefore you don't need to protect the toilet regardless of elevation compared to the water line. If you do end up with a vented loop it would be best installed with nothing between its top and the seacock except one run of uninterupted hose.

DavidL wrote:Once the tank is emptied and the pump is sucking air, will it still move the waste along downstream (after pump) and completly empty that line?

Probably not.