Washdown pump - suck or blow?

[AiniA]

Dumb question of the day. I will be installing a wash down pump on my Catalina 36. I can put the pump either close to the through-hull or close to the outlet forward. Does better sucking (close to the outlet) or better blowing (close to the inlet) make more sense or does it not really matter?

[sailorboy1]

Depends on if the pump will even suck

I would plan that it is better to have the pump below or at least close to the waterline depending on pump type

[rslifkin]

Most pumps suffer more from inlet restrictions than outlet restrictions. So put the pump closer to the thru hull.

[jamhass]

Originally Posted by rslifkin

Most pumps suffer more from inlet restrictions than outlet restrictions. So put the pump closer to the thru hull.

Yes, This

[AndyEss]

Putting almost any pump with its intake under positive pressure improves its performance.

Any leak on the suction side (which if you mount your pump above the water line will be under negative (relative to atmospheric) pressure and will admit air.
Air bubbles in your suction line will greatly degrade pump performance.
Think of positive pressure on the suction side as supercharging your pump

[Cadence]

Place it close to your intake. Much less likely to have a priming problem.

[Cadence]

I can't help myself. Suck, blow is only a figure of speech.

[a64pilot]

Also don’t forget to put in a place that’s easily accessed, but below the water line is best.

[Redline452]

Mine (installed by PO) had a long intake run from the forward head intake, through the forward cabin into the sail locker. Over time (and a couple of blocked inlet events) the nearly right-angle bends in the hose began to flatten out. Moving it was impractical (I really tried) so I replaced the hose with a spiral reinforced type that won't (so far) crush. My aft washdown also has a long run, but it's T'd from the aft head intake with only a foot of hose. In other words, blow, definitely blow.
Also consider how you will be getting power to the pump - sometimes more hose is easier than more wire.

[Bill O]

Originally Posted by Cadence

I can't help myself. Suck, blow is only a figure of speech.

...and it eventually comes down to personal preference.

[AiniA]

Seems unanimous (which is rarely the case on CF). Now on to anchors to have onboard.