Drain Hose Size for Rule 600?

[Cheechako]

Originally Posted by Dave22q

Seems to me that hoses will always empty back to the pump unless stopped by a check valve which can raise failure issues. The amount of flow back is the volume of the hose from the high point back to the pump. Velocity has nothing to do with it. All the water in the hose when the pump stops pushing will flow downhill.
The reality is that no bilge pump can totally empty the bilge due to the design of the cut off switch. If you want dry use a hand pump as much as you can then a large sponge or jack the boat up and drill a hole in the bottom :>). If anybody has discovered an easier way I would love to hear it.

The way was already mentioned, one of these to get the last out. https://jet.com/product/detail/eced9...3lcaAjpF8P8HAQ

[Gone2long]

Originally Posted by HopCar

Yes going to a smaller hose will reduce blow back. Never heard it called blow back but I like the term. Maybe Flow Back would be a better term.

I had a customer with a small space that accumulated water. He installed a small Rule pump designed for 3/4" hose. The flow back was enough to trigger the pump again and it would continuously cycle on and off. He reduced the hose size to 3/8" and eliminated the problem.

Thanks for your insights on this and past issues.


I had the same recycling problem and what I have done is to remove the automatic pump and replace it with one that works on a toggle switch. If we leave the boat for more than overnight, we drain the bilge dry by hand. As noted above, we have two big hand pumps for emergencies.


Not the best setup, but the one we have at the moment.

G2L

[Gone2long]

Originally Posted by topmast

Going to a smaller hose will definitely reduce the 'flowback' but when the pump is called to emergency duty, what then? usually two pumps .big one sits higher in the bilge and hopefully only gets used when the inevitable nasty happens.

Point well taken, and something to perhaps rig in the future. Right now, we would rely on large (1 1/4" hose) hand pumps (2) if we had a serious accident, along with the smaller bilge pump.

G2L

[Halifax Sailor]

so still discovering about my boat and this line brings up several questions. Should you figure out what rate of flow if you were to lose one or two or three of your thru hulls? so that the bilge pumps will keep up to what may be coming in? I have a 900gph johnson and a manual as back up. I only have 2 X 1/2 " intake; 1 X 2" out for head; 2 X 1.5 " for instruments. Not a mathematician but with all less than 1.5' below water line (less depth, less pressure?) does anyone know how to calculate if pump out matches or can over come water in with drastic all thru hulls leaking? Obviously, hitting something large enough to put major hole in hull, prob last thing you are worrying about is capacity at that time. life jackets, crew and radio alert then fill/fix the hole and then see if pumps can keep up? would be my concern at that time.

[Halifax Sailor]

ok, does this make sense?

air pressure 14.7 lb/sq"
2' below surface (approx) - .86 lb/sq"

diam of thru hull - .75"

2618 gal per hour??

am i missing something or is this a close idea of 1 thru hull breaking off? if it's true then i guess i am glad ii have plugs.


Calculator: Water Flow Rate through an Orifice | TLV - A Steam Specialist Company (International)

[Gone2long]

Originally Posted by Halifax Sailor

so still discovering about my boat and this line brings up several questions. Should you figure out what rate of flow if you were to lose one or two or three of your thru hulls? so that the bilge pumps will keep up to what may be coming in? I have a 900gph johnson and a manual as back up. I only have 2 X 1/2 " intake; 1 X 2" out for head; 2 X 1.5 " for instruments. Not a mathematician but with all less than 1.5' below water line (less depth, less pressure?) does anyone know how to calculate if pump out matches or can over come water in with drastic all thru hulls leaking? Obviously, hitting something large enough to put major hole in hull, prob last thing you are worrying about is capacity at that time. life jackets, crew and radio alert then fill/fix the hole and then see if pumps can keep up? would be my concern at that time.

Not me, I earned a D in Algebra, and I am not sure that bilge pumps are really designed to do such "heavy lifting".

But hopefully, someone more experienced or capable on the thread can give you an intelligent answer.

Regards,

G2L

[Halifax Sailor]

ok, does this make sense?

air pressure 14.7 lb/sq"
2' below surface (approx) - .86 lb/sq"

diam of thru hull - .75"

2618 gal per hour??

am i missing something or is this a close idea of 1 thru hull breaking off? if it's true then i guess i am glad ii have plugs.


Calculator: Water Flow Rate through an Orifice | TLV - A Steam Specialist Company (International)

[Dave22q]

Simple internet research. I used a super conservative PSI equal to a 50' depth because my first site used pump pressures and nobody makes pumps to push water at 2.2 PSI equating to a 5' depth. Flow rates by inside diameter are: 1/2" 14 GPM; 1.5" 81 GPM; 2" 127 GPM. So your predicted flow would be way less than the 50' rate of 317 GPM of which 40% is your toilet outflow (very unlikely to leak). The bottom line is that your bilge pump should be sized to handle major leaks and thru hull failures are not major.
https://flexpvc.com/Reference/WaterF...PipeSize.shtml
http://www.kylesconverter.com/pressu...er-square-inch
Unattended boats with no ongoing charging system sink from small leaks not because the pumps are overwhelmed but because the batteries eventually get drained or the pumps burn out. My suggestion is relax and don't worry about thru hulls. Focus on things like protecting your boat in your absence and carry some plugs. Hope this helps.