Bilge water flowing back to bilge

[JC Reefer]

No need to take on any risk with a check valve.

Fixing the leak is a need but does not remove the need to resolve the never ending bilge pump.

I’d try the following:
Raise the switch (will probably do it)
Upgrade to a Time adding switch
Maybe see if the hose can be adjusted to create a p-trap early in its run.

Maybe some photos will help.

[jtsailjt]

Originally Posted by Sea Q

I would be hesitant on a check valve could cause big time problems if it stuck closed

While I suppose a check valve could get stuck closed and cause a problem with a typical vane type bilge pump, it's unlikely to cause a problem if it's inline from a diaphragm pump since duckbill check valves on either side of the diaphragm is what makes this type pump work. Also, even IF it somehow gets stuck closed (how does that happen unless it somehow gets reversed?), then the higher level bilge pump that has no check valve would kick in when the water level rose to its level so the boat would never be in danger.

I have a duckbill type check valve on my lower, diaphragm type bilge pump and it's never jammed closed. However, I did accidentally get some small pieces of wood in my bilge that got stuck in it so it stuck open, which still allowed it to pump water but also allowed the water to drain back out of the hose when the pump stopped running until I took it apart and dislodged the splinter of wood that was stuck in it. Not a big deal.

[MJH]

Originally Posted by hd002e

When the bilge pump kicks in, it pumps about a quart of water out and when it stops that water flows back into the bilge. The users manual does not recommend using a check valve but the re-flow is just enoughto trigger the sensor (fully automatic bilge pump) so the pump goes into a futile cycle (every 20 minutes or so).

Aside from cleaning out the remainder manually, how does one deal with this?

The amount of water flowing back into the bilge is a function of the hose diameter and the length of the hose. That's why having two pumps, the larger main pump and a smaller pump for incidental pumping, is a good system. The hose length should be as short as possible while still getting above the water line. However, depending on the height that the hose must rise may call for the use of a larger pump to get the required pressure. Generally these small pumps use 3/4" hose while some large pumps get up to 2" in diameter. This setup ends up with the small pump working most of the time and will be cheaper to replace. If you are going to use a check valve, the small hose is the one to put it on leaving the large hose for maximum pumping when needed.

~ ~ _/) ~ ~ MJH

[Cadence]

Originally Posted by hd002e

When the bilge pump kicks in, it pumps about a quart of water out and when it stops that water flows back into the bilge. The users manual does not recommend using a check valve but the re-flow is just enoughto trigger the sensor (fully automatic bilge pump) so the pump goes into a futile cycle (every 20 minutes or so).

Aside from cleaning out the remainder manually, how does one deal with this?

Shorten you discharge hose if possible.

[Mike Banks]

Use a smaller diameter bilge outlet hose.

[Red Sky]

Try a WaterWitch bilge pump switch. They’ll run the pump 15 seconds after it stops detecting water, solved the problem for me.

[HopCar]

I agree with MJH. The hose holds enough water to trigger the switch after the pump turns off.

The answer is to install a small pump that uses a smaller diameter hose. I had a customer with a very small compartment that gathered water sometimes. Even a 3/4” hose held too much water. He took the smallest Rule Pump he could find and adapted a 3/8” hose to it. The problem was solved.

[sv.antea]

Agree HopCar. Many original bilge pump installations leave much to be desired. Here is what I have been installing on boats. Use small pump, 360 to 500gph and run it as short a run as possible using the semi-rigid tubing that just jams conveniently inside the discharge. If overboard discharge is too long, I tap it into galley sink drain. The tubing is smooth bore, discourages sharp turns (don't put any right angle connectors) and the volume contained is small, so that the little water will run back. The low output pump will suck in air later, so more water gets pumped out. Depending on the size of the boat, second, large bilge pump is installed with adequate crossection hose, also as low as possible in the bilge, but with it's float switch higher, so all the routine pumping is left to the small pump. In few difficult installations I have added timer to keep the larger pump on until its pulls air.

[GordMay]

Originally Posted by Dockhead

Why God made maintenance pumps.

The answer to this age-old problem is to have a small pump with a check valve, or a diaphragm pump, with pickup mounted in the lowest possible place in the bilge.

Then a bigger pump WITHOUT CHECK VALVE, with a higher mounted pickup and float switch.

Each with its own discharge hose and outlet.

Indeed.
Install a, manually switched (non-automatic), low capacity diaphragm pump (±3.5 GPM) such as the self-priming, dry running Jabsco/PAR 31705 Series diaphragm pump, and the bilge can be pumped virtually dry.
31705-0092 ➥ https://www.defender.com/product.jsp?id=84980

[twig]

If you put in a small lift pump where do you discharge that water to. Wouldn’t you also need a loop mounted high and that water run back into bulge too when pump shuts off?

[thinwater]

I see that the OP is in Connecticut. I'm guessing he stays in the water through the winter, but that is just a guess.



If a check valve is holding water and the cabin temperature goes below freezing, the hose will be blocked and the boat may sink. All it takes is an hour between cycles. I've seen it happen. It has to get pretty cold, but it is a critical failure.



Check valves are permissible, but they can clog, they always reduce flow, and in freezing climates they are a bad idea.

[jtsailjt]

Originally Posted by JC Reefer

No need to take on any risk with a check valve.

Fixing the leak is a need but does not remove the need to resolve the never ending bilge pump.

I’d try the following:
Raise the switch (will probably do it)
Upgrade to a Time adding switch
Maybe see if the hose can be adjusted to create a p-trap early in its run.

Maybe some photos will help.

What, exactly, do you perceive as a "risk" associated with using a check valve as has been described earlier in this thread? The only potential problem I see with one is that it creates an increase in resistance in the line so if it stuck closed could effectively clog the line. But this problem can be easily solved by using a pump that's powerful enough to overcome this added resistance. Small vane type bilge pumps aren't very powerful and are susceptible to being stifled by a check valve (see last paragraph below) and that's why it's best to use a diaphragm pump for this purpose, with a larger, much higher capacity, vane type pump (without a check valve) at a slightly higher level so if you spring an actual leak or the lower pump fails to keep the bilge empty, it's there to do the job. That's the arrangement I have in my bilge and the diaphragm pump has never clogged so the higher capacity, higher level pump has never been used except for one time when I shut off the lower pump and deliberately ran water into my bilge with a hose to verify that my vane type pump was working properly.

Raising the switch will just mean the water level in your bilge will increase by that amount and will not have any effect on how much water drains back out of the hose when the pump stops running. Unless the switch is raised to a point where the bilge is wider, so the water draining back out of the hose raises the level a lesser amount, this will not solve the problem.


Time added switch will stave off the backwash for the amount of additional time the pump runs, but when it eventually shuts off, the same amount of water will run back into the bilge.

A P-trap would be difficult to install because bilge pumps are generally installed at the lowest possible point. Also, it wouldn't have any significant effect on the amount of water that gets sucked back out of the hose and back into the bilge when the pump shuts off. If anything, the increase in length of the hose required to form the P-trap would add to the amount of water that drains back into the bilge. Better to have as straight and as short a run as possible to a thru hull above the heeled water line. Decreasing hose diameter will help with the problem of water draining back into the bilge but will also constrain the capacity of the pump by adding resistance.

I mentioned earlier the setup I have with a diaphragm pump with a check valve combined with a large capacity vane type bilge pump without a check valve higher in my bilge, but in my dinghy I have a different arrangement that I think is common to many smaller sailboats. My dinghy is an Achilles RIB and it has a very small (approximately 6"X6") sump which is against the center of the transom so that's the obvious place to mount a bilge pump. I have one of those little automatic water sensing Rule bilge pumps mounted here with about a 2' loop up to a thru-hull I mounted a few inches below the top of the transom. Even though hose is small diameter, once the pump shut off the water would drain back and refill the small sump, once again triggering the pump to run, a never ending cycle. So, I added a duckbill type check valve just above the outlet from the bilge pump, but this proved to have too much resistance for the pump to overcome so the pump would run but no water come out of the hose. So, next I replaced the duckbill type check valve with one of those with an internal flapper that has a rubber washer on it to help it seal. This worked great for awhile, until one day my dinghy had water in it and my bilge pump wasn't running but the battery wasn't dead and when I turned in manually on it would run but no water came out. It took me some head scratching to figure this one out but eventually I realized that my flapper type check valve was effectively blocking the water from draining back into my bilge via the bilge pump, but it also was creating the possibility for an air bubble to form between it and the base of the bilge pump so the bilge pump would run but would be trying to pump air rather than water. So, my fix for this problem was to drill a small hole in the top of the hose just after it exits the bilge pump but before the check valve so no air bubble can be created here and as the water rises in the sump, it also rises inside the bilge pump so when it is triggered on, the vanes in the pump have water to pump rather than trying to pump air. So, now when my bilge pump runs I have a tiny geyser (angled slightly away from the right side where I sit) coming out of the 2" section of hose that's between my bilge pump and the check valve, but I no longer have a problem with my dinghy's bilge pump becoming air bound as the boat rocks with little water in its sump.

[aeronautic1]

A typical small boat bilge pump, like a Ruhle, is a centrifugal pump. It does not pump air. The float switch shuts off before all the bilgewater is expelled. Therefore, all of the water between the pump and the top of the anti-syphon flows back to bilge. Unless you have a back-up diaphragm, vane pump or bucket and sponge, there will always be residual water. Have you looked into the ARID BILGE SYSTEM?

[Bill O]

Originally Posted by aeronautic1

Have you looked into the ARID BILGE SYSTEM?

+1 for the arid bilge pump. It may be overkill but it does suck out the last bit of water that may be unable to be removed be removed by normal pumps (hose dead volume).
As suggested, double check that you don't have a leak by mopping up the residual then see if the pumps kick on as frequently.


Bill O.

[jtsailjt]

Originally Posted by aeronautic1

A typical small boat bilge pump, like a Ruhle, is a centrifugal pump. It does not pump air. The float switch shuts off before all the bilgewater is expelled. Therefore, all of the water between the pump and the top of the anti-syphon flows back to bilge. Unless you have a back-up diaphragm, vane pump or bucket and sponge, there will always be residual water. Have you looked into the ARID BILGE SYSTEM?

WOW, that seems like a great system, but expensive too.

There's also a DIY version mentioned online that they claim costs only $100 and uses a sponge at the pickup(s) and a timer on the diaphragm pump rather than moisture sensing to trigger the pump on. Sounds like a great idea to me! 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. It seem to me like they'd be especially useful in shallow bilged boats where you have easy access to the pickup points so clogging in the tiny hoses doesn't become an issue. On my boat I can barely reach to the bottom of my bilge so access to pickups would be difficult and the inch or so of water that's always down there isn't too big of a problem. But what a great idea to help reduce odor and mildew causing moisture in the bilge.