Stupid bilge pump design or...?

Daveinet · Jan 28, 2015

The crux of his problem is the panel won't charge the batteries if the pump is on. So there needs to be a way to disable the pump until the battery has enough charge to run the pump at full speed, so it will actually pump. There are some cheaper circuits with simple low battery alarms. The alarm could be removed and a relay installed instead. Just need to find a circuit with some hysteresis built in.

Scott T-Bird · Jan 28, 2015

What are you missing?

Stephen Trapani said:
BTW, the way I have this figured at the moment, this isn't just my problem, it's the problem of every boat owner who doesn't have a low battery cutoff. Once your battery charge gets low enough it will cause your bilge pump to run (once the float switch turns on) without pumping out water. This will keep your battery drained indefinitely even if you have any kind of slow charger on it like a solar panel. What am I missing?

Why does your charge drop to a low level where the pump doesn't operate at the necessary capacity? If you have a solar panel and you leave the boat for a long period, why doesn't the solar panel keep your batt topped off?

It sounds like you have a failed battery bank and you are blaming it on the bilge pump. If your batts were good, and the solar charger is working, then you should have no problem maintaining enough juice for the occasional need for bilge pump. If your bilge pump is operating while you are away from your boat, aren't you concerned about the water leakage which is causing the bilge to switch on?

It seems like you have a battery issue and a leakage issue, and you are trying to chase down a reason why your bilge pump isn't functioning the way that you think it should.

uncledom · Jan 28, 2015

Stephen, we're thinking the reason the battery is low is because of the cycling. You would need to fix the underlying cause and not just concentrate on the effect.

Maine Sail · Jan 28, 2015

Stephen Trapani said:
Thanks for the answers guys. FWIW, I did replace the float switch and pump (twice!) before I figured out what was going on (I'll leave out the dark, rain, 4 paddle outs, climbs up the stairs, and drives to the store). I just couldn't believe that my solar panel would never be able to charge a low battery bank due to this design of pump, and that this was common. I guess it is.

The low battery cut off should solve it and looking at it's price, I guess that's why it's not a standard feature of bilge pumps. Don't know why I haven't run across this problem before, or why it doesn't cause a lot more problems for people.

These problems are generally related to a number of issues:

#1 Poor bilge switch chosen for the task - Ever since the removal of mercury from the Rule etc. float switches the relaibaility has been about as good as a Yugo. How to Rx? Don't buy unreliable products. The switches from Ultra Safety Systems are about as reliable as they get.

#2 Inadequate bilge pump system design - A good bilge pump system makes use of a "nuisance pump" which is a diaphragm style and an emergency pump or oh $hit pump which is a high capacity centrifugal type. The nuisance pump does all the routine work and the oh $hit pump is used only in emergency situations and the switch is mounted slightly higher in the bilge.

#3 Improper system design and install - Centrifugal pumps should NOT have check valves installed in the outlet hose. Check valves are a band-aid at best and owners choose them over a proper installation and should not. They are flat out dangerous at best and battery killers at the very least. It is one of the number one causes of destroyed battery banks other than cheap bilge switches. Centrifugal pumps should also use smooth walled hose, utilize a siphon break and have as few bends as possible. Wire should be sized for the least voltage drop. Centrifugal pumps will never pump anywhere close to their rating "as installed" so the biggest capacity oh $hit pump you can fit is the best choice.

#4 Nearly all new battery chargers, solar controllers etc. will not charge into a low battery for simple safety reasons. The reasoning is that a 10V battery has lost a cell and experienced an internal failure such as a short. You certainly don't want to lose a cell and then continue charging the battery.

Best bet to avoid these issues:

Install a well designed bilge pumping system utilizing a nuisance pump (diaphragm type). Use quality bilge switches such as those by Ultra Safety Systems, use sufficient wire for minimal voltage drop, use water proof splices for all wiring terminations, make all terminations above bilge height when ever possible, fuse the pumps per manufacturers recommendations and do not use a check valve on any centrifugal type pump. Check valves are fine on a diaphragm pump but a very bad idea on a centrifugal bilge pump...

Sadly the best bilge switch ever made was discontinued because boaters refused to pay for the technology and reliability. I bought an extra before they ran out....

That said I have yet to have or see an Ultra Safety Systems bilge switch fail....

Charles Erwin · Jan 28, 2015

MaineSail's list represents his usual thorough analysis.

Only one of the things he discusses explains what you describe - apart from the possibility you have an obstruction or leaking connection in the discharge hose or its fittings.

The voltage at the pump motor is severely degraded for some reason you say and the installation of a new pump did not alter the symptoms.

Measure the voltage at the battery and then measure the voltage downstream - as close to the pump as you can (probably at the connectors you used to hook up the pump pigtail.) Accept nothing greater than a 3% variance either at rest or with pump running.

Charles

jwing · Jan 28, 2015

Maine Sail, I'm curious to learn why check valves should not be used with centrifugal bilge pumps. I've worked on hundreds of centrifugal pumping systems. They all have check valves and they all work just fine. Is there something different about a bilge pumps that I have not considered?

Gunni · Jan 28, 2015

jwing said:
Maine Sail, I'm curious to learn why check valves should not be used with centrifugal bilge pumps. I've worked on hundreds of centrifugal pumping systems. They all have check valves and they all work just fine. Is there something different about a bilge pumps that I have not considered?

Bilges are full of debris, from construction dust, food crumbs, to your own fur and they all can clog a check valve - at the worst possible time. Think of your bilge more like a debris filled basement - use a trash (diaphragm displacement) pump, not a centrifugal pump if you want reliability. I've had no problems out of my Water Witch solid state switch - no moving parts.

Charles Erwin · Jan 28, 2015

I think quantifying voltage (motor running, motor not running, at battery, at pump) will surely decide the matter and probably provide a decisive diagnosis. Yes?

mitiempo · Jan 28, 2015

Stephen Trapani said:
So are you saying that even at low battery voltage, the pump shouldn't spin without pumping out water? Others seem to have said above that the low battery voltage would cause the pump to spin without pumping out water. When I run the motor, the bilge pump works just fine. I'll check the voltage as you suggest when I get back there especially if the bilge isn't working again.

As your pump works with the motor running but it doesn't work otherwise I would think the battery bank is the issue.

centerline · Jan 28, 2015

Stephen Trapani said:
BTW, the way I have this figured at the moment, this isn't just my problem, it's the problem of every boat owner who doesn't have a low battery cutoff. Once your battery charge gets low enough it will cause your bilge pump to run (once the float switch turns on) without pumping out water. This will keep your battery drained indefinitely even if you have any kind of slow charger on it like a solar panel. What am I missing?

if your missing anything at all, i would say its the concept of keeping the battery fully charged... if the current solar panel cant do it, you may need a bigger one.

this is assuming the battery is in acceptable condition, which i am questioning from the dialog that i have read concerning your issue.

because if your battery is in fact good and fully charged, when the pump kicks on, it will have plenty of energy in it to pump the water down and have lots of reserve left over when finished with its cycle....and assuming you dont have water running into the bilge unnecessarily from a hole somewhere, the solar panel will have adequate time to replenish the amps used from it on the last pump cycle....and be ready for next time.

with this said, I understand your focus on the seemingly odd behavior of float switch, but its a moot point if the battery is charged as it should be...

Now... you may ask my why the battery charge is more important than your idea of how the float switch should work in relation to how you see it working.....
my answer is,
#1.. because a battery with low voltage is extremely hard on any and all equipment that is trying to suck enough power out of it to run correctly.
#2.. because a discharged battery is not a dependable source for running a bilge pump
#3.. you obviously want the bilge pump to work all the time when it should, not just when you are around to help it function.
#4 if the battery stays charged, the way the float switch works when the battery is low is not and never will be an issue. problem solved!!!

dont overthink the symptoms, just solve the problem and the symptoms will go away

mitiempo · Jan 28, 2015

Fixing leaks might be a good idea as well. There is no good reason for any water in the bilge of a fiberglass boat in good condition. The only water entering should be from the stuffing box when the engine is running only - at rest no drip. If you have a PSS no drip at all.

Maine Sail · Jan 29, 2015

centerline said:
if your missing anything at all, i would say its the concept of keeping the battery fully charged... if the current solar panel cant do it, you may need a bigger one.

this is assuming the battery is in acceptable condition, which i am questioning from the dialog that i have read concerning your issue.

because if your battery is in fact good and fully charged, when the pump kicks on, it will have plenty of energy in it to pump the water down and have lots of reserve left over when finished with its cycle....and assuming you dont have water running into the bilge unnecessarily from a hole somewhere, the solar panel will have adequate time to replenish the amps used from it on the last pump cycle....and be ready for next time.

with this said, I understand your focus on the seemingly odd behavior of float switch, but its a moot point if the battery is charged as it should be...

Now... you may ask my why the battery charge is more important than your idea of how the float switch should work in relation to how you see it working.....
my answer is,
#1.. because a battery with low voltage is extremely hard on any and all equipment that is trying to suck enough power out of it to run correctly.
#2.. because a discharged battery is not a dependable source for running a bilge pump
#3.. you obviously want the bilge pump to work all the time when it should, not just when you are around to help it function.
#4 if the battery stays charged, the way the float switch works when the battery is low is not and never will be an issue. problem solved!!!

dont overthink the symptoms, just solve the problem and the symptoms will go away

Today's run of the mill, non-mercury, float switches are horribly unreliable. If a float switch sticks, it kills the battery. Simple stuff that happens every single day...

Stephen noted his float switch was sticking thus the switch likely killed the battery not the other way around.. I see this over, and over, and over, and over, and over, and over, and over. You fix it by installing a good quality float switch. Replacing it with the same switch will eventually result in the same problem. I have seen $2000.00 battery banks destroyed by a $30.00 float switch simply trying to remove nuisance water when it stuck in the on position.

I have also seen boat fires caused by a float switch that stuck on when tied to a dock.. The charger kept the batteries charged & the pump running but the bilge pump eventually burned up the bearings, locked the rotor and burned the vessel. This is why it is critical to never over-size a fuse on a bilge pump beyond where the manufacturer suggests.

Hopefully the battery was not permanently damaged...

Stephen Trapani said:
Got to my boat a couple weekends ago and found the bilge pump wasn't working. Very long story short (the long story was about how long it took me to figure it out! I think the float switch went bad, failing to turn off when down), I discovered that when the battery bank is low the off-the-shelf Rule pump runs, pushing water out of the pump, but isn't strong enough to pump water all the way out of the above waterline discharge. So it will just run and run, pumping nothing until it completely drains the battery bank. When my solar panel manages to charge the bank a little, the pump will start up again, pumping no water out of the bilge, running until it drains the battery entirely.

Is this the way a bilge pump is supposed to work?

If the float switch failed and drained the battery you will eventually get to a point where the centrifugal pump can no longer overcome the head pressure, as installed.... Also if you have a check valve in the discharge line, as many incorrectly do with centrifugal pumps, then your pump may never open it, even with a fully charged battery. I see this almost weekly during the boating season. Pumps sitting there cavitating (bubbling & spinning) because they simply can't overcome the weight of the water behind the check valve..

These centrifugal pumps, and their flow, are directly related to installed system head pressure & voltage. They are rated at "open bucket" (zero head pressure) and charging voltages. This marketing is not only pure BS it is borderline criminal. An installed centrifugal pump will NEVER pump at open bucket rate and they rarely have charge voltages when doing so. The average installed 2000 GPH pump will be lucky to pump 700 gallons, and that is a good installation......

Maine Sail · Jan 29, 2015

jwing said:
Maine Sail, I'm curious to learn why check valves should not be used with centrifugal bilge pumps. I've worked on hundreds of centrifugal pumping systems. They all have check valves and they all work just fine. Is there something different about a bilge pumps that I have not considered?

There are a number of reasons but the number one should be that Rule specifically advises against it!!

These valves quite often stick shut especially if the bilge pump does not cycle often. The biggest draw back is the added head pressure that the pump can not overcome during start up. This additional head is caused by the standing water in the discharge hose, and thus, a centrifugal pump will simply cavitate and do nothing but make some neat little bubbles in the bilge.

For boats stored in-water during cold weather, the water in the bilge hose above bilge level, can freeze when the bilge water is not frozen. This present an impossible situation to pump into.

For boats with "automatic" resistance checking bilge pumps (please don't use one of these) they can cause them to not work at all.....

Fill a grain silo with corn and then try to push a door open into it...... Pretty tough. The check valve creates the same type of resistance to the centrifugal bilge pump. Centrifugal pumps, like those from Johnson, Rule etc. deal horribly with any added head pressure..

Check valves on rotary vane pumps or diaphragm pumps do not suffer the issues they do on centrifugal Rule style pumps. I have seen everything from ruined interior cabinetry, cabin soles and engines due to stuck check valves. I have also seen boats that sank because of a stuck check valve.

The largest maker of centrifugal bilge pumps, Rule, specifically recommends not to use them.

They can be a danger if used on a system with centrifugal bilge pump. Bilge pumps are safety items anything that can prevent the pump from pumping becomes a potential danger.

They also eventually fail and allow the water you were trying to keep out, to drain back in, creating pump cycling. They are simply not a substitute for a well designed bilge pumping system despite numerous builders cutting these corners....

Rule Pump Instructions

Even the ABYC recognizes the reliability issues with check valves and specifically prohibits them for use as back flow or siphon protection.

ABYC:
22.8.6 The discharge location shall be above the
maximum heeled waterline, or

22.8.7 the discharge may be located below the
maximum heeled waterline if the discharge line is provided
with both of the following:

22.8.7.1 a seacock installed in accordance with the
requirements of ABYC H-27, Seacocks, Thru-Hull
Connections, and Drain Plugs, and

22.8.7.2 a vented loop or other means to prevent
siphoning into the boat. A check valve shall not be used for
this purpose.

And this is direct from Rule Pump:

"The Rule Pumps FAQs:

Can I install a check valve on the pump discharge?
Check valves are not recommended

Why doesn't Rule Pumps want check valve on the pump's discharge?
Check valves are prohibited by the American Boat & Yacht Council for use as an anti-siphon device-and with good reason: They're notorious for failing in both the open and the closed position, which respectively leads to flooding or failure to pump. If the valve is close to the pump, the pump may not be able to overcome the weight of the water on the other side of the valve, rendering the pump ineffective.

Why does my automatic Rule Pumps turns off if I install a check valve on the discharge of the pump?
The automatic bilge pump turns on about every two and a half minutes to "check" for high water. If water causes resistance on the pump, it continues to pump until the resistance lowers. With the check valve installed at the pump, it cant feel the weight of the water, and shuts off, allowing the bilge to fill with water!"

TropicalSeattle · Jan 31, 2015

Not exactly confidence inspiring. The new Beneteau Oceanis line has a Rule centrifugal pump, on corrugated hose, with a check valve near the pump. This check valve was recently replaced on some models due to a "service bulletin", apparently by a different check valve. No fundamental design changes, and this is exactly what seems to cause so many problems. I need to upgrade my pumps.