Washdown pump location

[Tim22]

I would like to install a washdown pump and am planning on t-ing off the head intake. Is It necessary to install the pump above the waterline? I have several possible locations below the waterline but no good options above.

Thanks
Tim

 

[sail sfbay]

Great question!!

You have a good plan to supply the washdown pump from an existing through-hull fitting, typically either the galley or head intake. A Y-connector lets the through-hull do double duty. Double clamp all hose connections below the waterline. Pumps push better than they pull, so mount the pump as near the through-hull as practical. A check valve installed in the hose connected to the other side of the Y-connector will prevent prime problems and eliminates the need for manual valves. A second check valve is required on the outlet side of the pump to prevent backflow, but most deckwash pumps are equipped with this valve.

You might find this article by Don Casey helpful: Installing a Deckwash Pump | BoatUS
and these: How to Install a Boat Washdown Pump | Boats.net Choosing and Installing a Washdown System | West Marine

 

[Ken Cross]

Great question!!

You have a good plan to supply the washdown pump from an existing through-hull fitting, typically either the galley or head intake. A Y-connector lets the through-hull do double duty. Double clamp all hose connections below the waterline. Pumps push better than they pull, so mount the pump as near the through-hull as practical. A check valve installed in the hose connected to the other side of the Y-connector will prevent prime problems and eliminates the need for manual valves. A second check valve is required on the outlet side of the pump to prevent backflow, but most deckwash pumps are equipped with this valve.

View attachment 195228

You might find this article by Don Casey helpful: Installing a Deckwash Pump | BoatUS
and these: How to Install a Boat Washdown Pump | Boats.net Choosing and Installing a Washdown System | West Marine

Just curious why you would want a check valve for backflow prevention on a wash down pump?

 

[sail sfbay]

Check valve stops backflow from the pump to mitigate loss of prime on the suction side unless you have a self-priming, positive displacement, e.g. diaphragm, pump.

 

[Sailor Sue]

Regarding the diagram, would it make more sense to have the check valve on the Intake side of the pump to keep the pump full?

 

[sail sfbay]

Sailor Sue..........possibly, but a check valve in the suction it imposes pressure drop and can cavitate and damage the pump. The suction loop acts as check valve and mitigates backflow from the pump. The discharge check valve mitigate loss of system water column.

 

[Tim22]

Any thoughts on whether the washdown pump needs to be above the waterline?

Tim

 

[sail sfbay]

Any thoughts on whether the washdown pump needs to be above the waterline?....

Above the waterline is Ok if it is a self-priming pump and safer in the event the pump leaks. Same question cam up on these threads:
Questions on installing a salt water wash down pump | Downeast Boat Forum
Wash Down Pump | Bloodydecks (bdoutdoors.com)

 

[Jollyroger]

Why not just make a portable washdown/anchor wash pump in about ten minutes? Then you could also pump out a dinghy and wash anything else with freshwater or seawater. See an article on my website DECKWASH (schooner-britannia.com)

 

[sail sfbay]

Jollyroger.........great suggestion, thanks for sharing!!