Head Pumping

[Stu-L]

On my 34 Californian I have a Sealand diaphragm pump that pumps wast over the side through a through hull fitting. If I close the through hull fitting the pump will divert wast to the deck fitting. There is about four feet from the holding tank and the deck fitting.

Question If I close the through hull, open the deck fitting incert the pump a head nozzel, turn on the pump a head and then turn on the Sealand pump for extra boost to get wast to the deck fitting will the suction of the pump a head damage the diaphragm of the Sealand pump.

 

[psneeld]

Threres no reason to turn on the pump if the pump out system is working OK.

I would think there would be no advantage, probably no damage, but why risk it?

Its late and cant get my head around what exactly would be bad....

....other than if the pump out suction is so much greater than the boat pump, the pump out would be pulling the boat pump diaphram down while its motor is trying to pull it up.

 

[Comodave]

I see a potential problem with turning on the pump while doing a pump out to shore, if the hose going from the deck fitting to the shore side pump comes loose, you will be pumping the effluent all over you and your deck. Ever see the movie RV?

I would rather have the Y valve before the Sealand pump and have a straight shot up to the deck mounted pump out fitting. Then you have the Sealand pumpinline when pumping overboard.

 

[HeadMistress]

You should only use the SeaLand pump to discharge the tank via the thru-hull. It's not needed for pumpout...dockside pumpout equipment doesn't need any onboard help.
All you need to do is make sure the y-valve is in the right position...that is, IF there is a y-valve in the tank discharge line. If there's only a tee, you don't need to do a thing except open the seacock and turn on the pump if you want to pump overboard or open the deck pumpout fitting to pump out.

However...If I close the through hull, open the deck fitting incert the pump a head nozzel, turn on the pump a head and then turn on the Sealand pump for extra boost to get wast to the deck fitting will the suction of the pump a head damage the diaphragm of the Sealand pump.

That would actually work...but if you decide to try it, I strongly strongly recommend that you make sure the boat is positioned to put the pumpout fitting is on the LEE (UPwind) side of the boat and that no one stands anywhere near it. Or have someone with a video camera at the ready a safe distance away.

 

[HopCar]

Seems an odd set up to me. Most systems have a direct connection from the tank to the deck fitting. No pump needed as the shore facility will do the pumping.

Like Comodave said, you don't want to pressurize that line. The fitting on the shoreside pumpout hose is meant for suction, not pressure.

I see Peggie beat me to it again! You really should buy her book.

Peggie, that would be a great video! Nice touch to your answer.

 

[BerettaRacer]

I've used a system like that a lot. Normally use my pump to discharge downward ovbd. but also have the option of pumping up thru the deck fitting. We use the deck fitting a lot to pump into a shoreside tank when in service shipyards, especially drydock. I had a third option of a direct tank suction from the deck fitting, bypassing the pump for a standard marina pump out. Had a fourth option of using the bilge pump to empty the waste tank in a main pump failure situation.