Bilge pump system design help required please: (Deep bilge)

[JeremyFowler]

1) Outlet: I hope to use an existing unused 1inch through-hull fitting (with stopcock of course), well below waterline, using a riser and anti-siphon point. OK? (I had wondered about having a mini-sink sort of arrangement where the outlet exits into a mini-sink which exits through the through-hull fitting, the advantage being that one could plug a manual diaphragm pump into the outlet and manually pump out through the pump should the electrical pump malfunction. )
2) As the sump is too deep to comfortably reach I thought to have the whole bilge pump inlet contraption installed into a sieved pipe which is then lowered into the bilges. This should also enable the sieve to be easily cleaned, etc. OK?
3) Can I use just the one exit pipe to feed off 2 bilge pumps? Probably not without using a non-return valve, which seems to be a no-no according to what I’ve researched on this site. If there is a good way around this it will save having extra piping getting in the way.
Any other pointers gladly taken into consideration too.
Cheers!

[John_Trusty]

I have not seen a bilge pump discharge below the waterline, as you described. The problem is the draining head will only be the difference between the highest point (say your vented loop) and the waterline, and the volume involved. For a small centrifugal pump dumping even 600 gallons (2,200 ltr) per hour, that's 10 gal per minute which would quickly overwhelm the small volume in that outlet that is above the waterline, at which point the pump stops moving water because these high capacity pumps are notorious for low head pressure.

Try reading through this from Practical Sailor: https://www.practical-sailor.com/wp-...BILGE-PUMP.pdf

[Rumrace]

Smaller sailboats have one pump. It exits well above the waterline and possibly to both sides. By code it’s to have an alarm and an float switch.
A power boat will have two bilge pumps with the automatic float switch and alarm being the one in the engine room and the cabin being manual. Most have override manual switches all have lamps and fuses. Fuse should be rated to the pump. Nothing else should be on the same circuit. A Sink will discharge above the water line. Nothing leaves the boat under water save the exhaust water from engine or generator mounted slightly above the water. Any hole under the water line should have a solid seacoack and a sea strainer.
Buying a pump with long leads is a great idea if your new to wires in wet areas.

[Uncle Bob]

Originally Posted by Rumrace

Smaller sailboats have one pump. It exits well above the waterline and possibly to both sides. By code it’s to have an alarm and an float switch.
A power boat will have two bilge pumps with the automatic float switch and alarm being the one in the engine room and the cabin being manual. Most have override manual switches all have lamps and fuses. Fuse should be rated to the pump. Nothing else should be on the same circuit. A Sink will discharge above the water line. Nothing leaves the boat under water save the exhaust water from engine or generator mounted slightly above the water. Any hole under the water line should have a solid seacoack and a sea strainer.
Buying a pump with long leads is a great idea if your new to wires in wet areas.

Where do you get these "codes" from, so many that you quote are at odds with reality.

[boatpoker]

Originally Posted by Rumrace

Smaller sailboats have one pump. It exits well above the waterline and possibly to both sides. By code it’s to have an alarm and an float switch.
A power boat will have two bilge pumps with the automatic float switch and alarm being the one in the engine room and the cabin being manual. Most have override manual switches all have lamps and fuses. Fuse should be rated to the pump. Nothing else should be on the same circuit. A Sink will discharge above the water line. Nothing leaves the boat under water save the exhaust water from engine or generator mounted slightly above the water. Any hole under the water line should have a solid seacoack and a sea strainer.
Buying a pump with long leads is a great idea if your new to wires in wet areas.

I know you never answer questions after these ridiculous claims but for once please cite this mythical "code".

[boatpoker]

Originally Posted by JeremyFowler

1)
3) Can I use just the one exit pipe to feed off 2 bilge pumps? Probably not without using a non-return valve, which seems to be a no-no according to what I’ve researched on this site.

Sorry, don't know NZ rules but ABYC are the most common standards used in NA and they require one pump, one hose and one throughull with no other connections as it risks a siphon effect.

[ItDepends]

Originally Posted by Rumrace

Smaller sailboats have one pump. It exits well above the waterline and possibly to both sides. By code it’s to have an alarm and an float switch.
A power boat will have two bilge pumps with the automatic float switch and alarm being the one in the engine room and the cabin being manual. Most have override manual switches all have lamps and fuses. Fuse should be rated to the pump. Nothing else should be on the same circuit. A Sink will discharge above the water line. Nothing leaves the boat under water save the exhaust water from engine or generator mounted slightly above the water. Any hole under the water line should have a solid seacoack and a sea strainer.
Buying a pump with long leads is a great idea if your new to wires in wet areas.

"By code"... What "CODE" exactly? You are making stuff up AGAIN...

[boatpoker]

Originally Posted by ItDepends

"By code"... What "CODE" exactly? You are making stuff up AGAIN...

He's not going to answer. He pulls this stuff all the time.

[coopec43]

c.Pumpintakes shall beprotectedto prevent ingestionofdebris that are likelytocausepumpfailure.
d.Intake tubing,ifused, shallnotcollapse under maximum pump suction.
e.Pumpdischarge systems shall beasnonrestrictiveaspracticable.
NOTE:Pump discharge capacityasinstalled may be reducedbysuch factorsas:
-lengthofdischarge piping,
-number and radiusofbends,
-roughnessofthe interior surfacesofpiping and fittings, and
-reductionincross-sectionalareaofdischarge system components suchascheck
valves andthm-hulls.
f.The discharge location shall be abovethewaterline createdbymaximum conditionsofthe boat's
loading, heel, trim and motion astern.
EXCEPTION:The discharge may be located below the waterlineifthe discharge lineisprovided
with a vented loop to prevent siphoning into the boat.A check valve shallnotbe
used for this purpose.
©1986 American Boat andYachtCouncil,Inc.


https://law.resource.org/pub/us/cfr/ibr/001/abyc.H-22.1986.pdf


Yachting/boating codes.
https://www.google.com.au/search?q=yACHTING+SAFETY+CODES&ei=t1RsY5L9KK6OseMP oIWT4AM&ved=0ahUKEwjStL79u6L7AhUuR2wGHaDCBDwQ4dUDC A4&oq=yACHTING+SAFETY+CODES&gs_lcp=Cgxnd3Mtd2l6LXN lcnAQDEoECE0YAUoECEEYAEoECEYYAFAAWABgAGgAcAF4AIABA IgBAJIBAJgBAA&sclient=gws-wiz-serp

[wyb2]

Originally Posted by boatpoker

He's not going to answer. He pulls this stuff all the time.

Are we 100% sure rumrace isn’t a bot? Answers every new thread almost immediately. Most responses are mildly confusing but relatively on topic, some could be considered helpful, then once in a while they are just completely off in left field and hard to even read. Very AI behavior: does an OK job of seeming human most of the time, occasionally pulls it off really well, and occasionally fails massively.

[HTurner]

https://stevedmarineconsulting.com/w...umps147_05.pdf

[Bowdrie]

Regarding posts that are in many cases grounded in smaller power boats, I would posit that it's quite important to have a bilge pump located right back where the bottom meets the transom.
Many powerboats frequently operate in a bow-high/stern-low attitude.
In that scenario water coming into the boat will flow aft until it reaches the transom.
Bilge pumps in more forward sections of the hull may never even come on or activate any lights/alarms until flooding becomes sufficient to alert the crew that any danger exists, (as the stern continues to settle).

[Searles]

Have successfully made and used grp and pvc manifold all entrys on the top with vlvs the entire unit close to centre line and above the w/l to a single over board discharge above or below the w/l ,the manifold is to have a breather to a high point ,all pumps including manual into the manifold .⚓️⛵️

[Uncle Bob]

Originally Posted by wyb2

Are we 100% sure rumrace isn’t a bot? Answers every new thread almost immediately. Most responses are mildly confusing but relatively on topic, some could be considered helpful, then once in a while they are just completely off in left field and hard to even read. Very AI behavior: does an OK job of seeming human most of the time, occasionally pulls it off really well, and occasionally fails massively.

You may actually be on to something, I would say that most responses are well wide of the mark and as such could be as you suggest.

[s/v Jedi]

I don’t like the underwater thru-hull for bilge pump discharge at all. I think your boat must have had a bilge pump before so there should be provisions for it, like a thru-hull above waterline etc.

I also don’t like the anti-siphon loop. I have standpipes, which I love, but I vent them with a fitting above deck so that there is no opening into the interior at all.

For capacity, I like the submersible bilge pumps. You can make a bracket to lower it into the bilge, then fasten the bracket against a frame in the bilge to keep it down and in place.