Bilge water flowing back to bilge

[GordMay]

Originally Posted by jtsailjt

... None of these are advertised to save your boat in the event of a leak but seem like they'd be a great way to get that last bit of water out if having dry bilges is important to you...

Indeed!
The primary drying pump that keeps your bilge dry is not the same as the secondary emergency pump that keeps your boat from sinking.
Smaller amounts of water are removed by the primary drying/normal dewatering diaphragm pump.
The high-volume secondary centrifugal bilge pump takes care of emergency inflows.

[GrowleyMonster]

The pump in the very bottom of your bilge should be a small one and the discharge hose also small, so it holds less volume of bilgewater and less to backflow. Keep it on manual, if it is automatic. Then it won't cycle on and off. Then a higher pump with high capacity and a larger discharge hose to deal with serious water, on automatic, to protect the boat in the event a hose or fitting or whatever lets go. Give the small pump a daily go, and the big one should never see water, but is ready for the worst. A portable submersible pump is a good backup, too, and a hand pump is the ultimate backup, no batteries needed. Have a genset mounted open? Can you add a PTO or mount a pump to run off the alternator belt? There is another good backup.


It could take that long for the water in the discharge hose to backflow into the bilge. The way to see if you are making water is to drain the bilge pump discharge hose and suck the bilge dry with a shop vac. Empty the shop vac. Check the bilge in an hour. No water or not much? Check it again in another hour or three or 24. Vacuum up any water and measure, divide by hours. I bet you aren't making any water other than a drip from your stuffing box, but if you are, time to look for the leak. Forward of your bilge well, build a dam out of clay. Another one aft of the bilge well. Which one fills up? There. You have isolated to one end of the boat, or the other. Continue and you will narrow it down.



Easy thing to check... common culprit when the water amount is small but noticeable, is your sink drain. Check your raw water intakes, too. Shower? Head? No it won't smell if the leak is coming from the seawater side. But like I said, if you have a long run of large hose for bilge pump discharge, it can hold a good deal of water, and can take a while to backflow through the pump, and can cause exactly what you are experiencing. A second smaller pump manually controlled down deeper in the bilge is your solution. Remember, small discharge hose, as direct and short as possible. Do not use the same through hull for both pumps. A plastic through hull is fine, if it is nice and high above the waterline, where a bilge pump dishcarge should be.

[zeehag]

the water coming back into your boat is that water in the hose. it is ok. wont kill you will not sink boat.
when your check valve fails you can sink boat. why mess with this issue. is all good.
if you so dislike wet bilge, even a quart, then change entire bilge dewatering system to your liking.

[jtsailjt]

Originally Posted by zeehag

the water coming back into your boat is that water in the hose. it is ok. wont kill you will not sink boat.
when your check valve fails you can sink boat. why mess with this issue. is all good.
if you so dislike wet bilge, even a quart, then change entire bilge dewatering system to your liking.

No, the water from the hose won't sink boat but it can make the automatic bilge pump cycle endlessly and that is what the OP primarily wants to address.

Check valve won't sink boat unless it's used as a substitute for plumbing it to a thru hull below the water line and nobody has suggested doing that.

[zeehag]

Originally Posted by jtsailjt

No, the water from the hose won't sink boat but it can make the automatic bilge pump cycle endlessly and that is what the OP primarily wants to address.

Check valve won't sink boat unless it's used as a substitute for plumbing it to a thru hull below the water line and nobody has suggested doing that.

funny even in my shallow bilged ericson this issue was not an issue. the return didnot cycle my pump and no problems were ever seen.
1 qt water doesnot turn on the bilge pump unless it is inside a small containment area such as a shower sump. yes i know how many times my pumps cycle as i am damned near always on board..unless i am rowing across marina for parts or foods. then i can see the outflow portal on my dry bilges formosa. i keep my pump inside a collander for straining out of cat hairs.. works great. never has my pump in any of my 15 ish boats i have owned in my history ever had pump cycle from merely returning water from hose. perhaps you have a leakage issue from somewhere more serious than hose backflow.

[jtsailjt]

Originally Posted by zeehag

funny even in my shallow bilged ericson this issue was not an issue. the return didnot cycle my pump and no problems were ever seen.
1 qt water doesnot turn on the bilge pump unless it is inside a small containment area such as a shower sump. yes i know how many times my pumps cycle as i am damned near always on board..unless i am rowing across marina for parts or foods. then i can see the outflow portal on my dry bilges formosa. i keep my pump inside a collander for straining out of cat hairs.. works great. never has my pump in any of my 15 ish boats i have owned in my history ever had pump cycle from merely returning water from hose. perhaps you have a leakage issue from somewhere more serious than hose backflow.

The likelihood of the water in the hose making the pump cycle depends on the volume of water in the hose that drains back to the bilge (length and diameter of hose) and the area of the water surface at the height in the bilge where the float switch is located. In your shallow bilged boat it's not an issue because any water that drains back is spread out over a large area, but for those with a long run to the thru hull and a small, deep bilge, or for those with a bilge pump located in a small sump it can be a problem, thus this discussion.

[Tayana42]

Jtsailjt, my Tayana may have a different bilge shape and depth than yours but in my experience a smallish Jabsco PAR diaphragm pump remotely mounted under a saloon berth with a float switch in the bilge takes care of the small water. I have a larger vane type pump with the float switch 1” higher that takes care of anything more then the diaphragm pump can handle. Of course each bilge pump has its own separate through hull fitting and they are on separate circuits.

[jtsailjt]

Originally Posted by Tayana42

Jtsailjt, my Tayana may have a different bilge shape and depth than yours but in my experience a smallish Jabsco PAR diaphragm pump remotely mounted under a saloon berth with a float switch in the bilge takes care of the small water. I have a larger vane type pump with the float switch 1” higher that takes care of anything more then the diaphragm pump can handle. Of course each bilge pump has its own separate through hull fitting and they are on separate circuits.

Yes, that’s just what I have (different brand diaphragm pump though) but with a check valve inline since it’s a long run to the aft thru-hull and I want to prevent water from draining back into bilge. Everything else the same. Works great, knock on wood!

[hd002e]

Thank you all for the replies. I put an inline check valve in there and observing what it will do.

However, I noticed some behavior from the RULE 500 automatic bilge pump that I am not sure is normal. When I dunk the pump in a container full of water it does not turn on. The pump turns on for a brief period every 2.5 minutes, it stops immediately if there is no water but if there is water it goes on until the water is pumped out.

Is this normal?!

[thinwater]

Originally Posted by hd002e

Thank you all for the replies. I put an inline check valve in there and observing what it will do....

Is the boat in the water?

Be warned, check valves can freeze!! I have seen this contribute to sinkings in my marina twice. Same with low loops in the hose.


Most of the contributors may undervalue this risk, because they are in warmer places or because they haul the boat in the winter.

[hd002e]

Originally Posted by thinwater

Is the boat in the water?

Be warned, check valves can freeze!! I have seen this contribute to sinkings in my marina twice. Same with low loops in the hose.


Most of the contributors may undervalue this risk, because they are in warmer places or because they haul the boat in the winter.

Hi thinwater. The boat is in the Mediterranean and in the water. The lowest it wil go here is 50F. No concern over freezing but lots and lots of rain!

[stormalong]

Originally Posted by hd002e

Thank you all for the replies. I put an inline check valve in there and observing what it will do.

However, I noticed some behavior from the RULE 500 automatic bilge pump that I am not sure is normal. When I dunk the pump in a container full of water it does not turn on. The pump turns on for a brief period every 2.5 minutes, it stops immediately if there is no water but if there is water it goes on until the water is pumped out.

Is this normal?!

That is exactly how some automatic bilge pumps work. They measure the current flowing through the motor. If there is water there is a higher load on the motor and the pump remains on until the load is reduced, IOW there is no more water to be pumped.

[GrowleyMonster]

Originally Posted by hd002e

Thank you all for the replies. I put an inline check valve in there and observing what it will do.

However, I noticed some behavior from the RULE 500 automatic bilge pump that I am not sure is normal. When I dunk the pump in a container full of water it does not turn on. The pump turns on for a brief period every 2.5 minutes, it stops immediately if there is no water but if there is water it goes on until the water is pumped out.

Is this normal?!

If it is that type of pump, yes. It senses the resistance of the water to pumping. I suspect it simply senses the current through the motor windings but it could have a torsionmeter or something similar. Either way, when there is no more water, the pump turns more freely and the control circuit says okay, no more water, shut er down. Then it tries again later. Older pumps use a float switch. They never turn on untl the float switch closes.

[jtsailjt]

I have 2 of those Rule 500 Automatic pumps, one in my 17’ Boston Whaler and one in my 11’ RIB. In both boats they only have to raise the water 12-18 inches through a 2’ hose. The Whaler needs no check valve because the bilge is large enough so when the pump shuts off and water in hose drains back through the pump the water level doesn’t rise enough to trigger the pump back on. But in the RIB with only a small depression for a bilge the backflow triggered the pump back on so I added a check valve as you have. But as I explained in an earlier post, when it rained again the air in the pump held in place by the weight of the water above the check valve would prevent the water level inside the pump from rising as it rose outside the pump. With just air inside the pump the vanes spin freely and no water is sensed so the pump doesn’t kick on and remove the water in the boat. So to allow this trapped air to escape and allow the water to rise inside the pump I drilled a small hole in the hose about an inch from the pump and before the check valve. That seemed to solve the problem and it works fine now, though with a tiny geyser coming from the hole in the hose while the pump is running.

[thinwater]

Originally Posted by hd002e

Hi thinwater. The boat is in the Mediterranean and in the water. The lowest it wil go here is 50F. No concern over freezing but lots and lots of rain!

Ah! I don't think you said that and I could only guess from your CT signature.


Good luck!