another bilge pump question

[butchrobbins]

My bilge pump runs, but is not pumping anything out of the bilge. I took it apart this morning to make sure screen was clear and it spun fine-just not taking anything out.

Could the line be clogged? I have a check valve in the line, could this have failed?

I've been told not to have a check valve in the line, but what would prevent the water from just coming back down?

Lets have a vote: yes or no to a check valve.

 

[Tim R.]

No check valve. It will fail when you need to pump the bilge the most.

 

[Steve Dion]

Try back flushing the hose from the thru hull. You may have something caught in the line.

 

[Maine Sail]

Ditch the check valve they are a danger IMHO. Unless you have a diaphragm pump you really do not want a check valve. Centrifugal type pumps can't over come much head pressure. The water standing in the bilge line creates enough head pressure to prevent the check valve from opening and then the pump just cavitates. This is how we repaired many "broken" bilge pumps back when I worked in boat yards. Yank the check valve and the pump works again...

 

[MrUnix]

Disconnect the hose from the pump and see if it pushes water.. if it does, then it's your hose and/or check valve. If not, you might have a bad impeller or a clog inside the pump itself. Check valves are generally a bad idea because they trap water above the valve, which then allows munge and algae to grow (worse in salt water environments), eventually causing the valve to either fail completely (stuck closed) or only partially open. Try using a loop in the hose instead, and make the top of the loop the highest point in the system (and well above the waterline).. that will allow the water to drain out of the hose when the pump is not on and prevent buildup within the hose. My vote is 'no' on the check valve

Cheers,
Brad

 

[Bill Roosa]

Wire polarity

Do you have the wires hooked up correctly. If you hook them up backward the motor will dutifully run backward and not pump a dang thing. With the three wires for auto/manual control it can get a bit confusing and is pretty easy to get turned around.

 

[Steve Dion]

I guess you will not be able to back flush your line with a check valve in place.

The problem that you are having is "probably" the problem.

When you have doubt about water coming back you can alway make a loop right behind the thru hull. The loop would go up and then down held together with a wire tie.

 

[two sailors]

My old pump would air lock occationally. A stop and restart would get it pumping untill one day it would just not pump at all. At 28 years I retired it. Just in time I might add. A water line to the refridge detached last week (sloppy dewinterizing). I got a call from a moorage neighbor about water being discharged. Get rid of the check valve and buy a good pump!

 

[Benny]

No check valve. Backflow will be minimal with only some of the water left in the hose coming back down. The amount of backflow should not activate the float switch. If it does the float switch is incorrectly positioned and that may cause repeated cycling which may discharge the batteries. Check for the possibility that some bug may have decided to build his home in the discharge port.

 

[joe-fran]

I had the same problem with a boat a bought last summer (1988 ericson 28). Punp ran but not pushing water out the stern. Ditch the back flow valve. Disconnect the hose from the pump and test the pump - see if it pushs water out the pump OK. If not, it's the pump. If so, you have a clogged line. With the back flow valve removed and the hose disconnected from the pump, stick a hose in the stern outlet and back flow the hose. SHould clear the problem.

Joe

 

[tkanzler]

The problem with some sailboat bilges is that they're small but deep, so it doesn't take much water to raise the water level enough to activate the float switch. A check valve reduces the amount of backflow. It's not a great solution, but it's common enough.

A better solution is a very small bilge pump with a small discharge line so not much water volume washes back in when it shuts off. A large pump, mounted higher in the bilge with it's own float switch, would take care of problem water, like a real leak. It should never be needed, but it would be there just in case.

For the air-bound problem when using a check valve, if you're going to use one after all the recommendations not to, drill a small hole in the discharge hose on the pump side of the check valve to vent air when it starts. Drill it on the bottom side of the hose, near the check valve. It will shoot a little water when the pump runs, of course, which is why you put the hole facing back into the bilge, but it will allow the pump to catch a prime when it starts by venting air.

I have the problem of short-cycling on my H340, and I use a check valve. I'd rather use a smaller pump with small diameter hose, but I don't like the idea of only having a small pump, and I'd rather not spend the money and effort to have two pumps. The check valve with vent hole has worked for me for the last 5 years or so, since I got the boat, so that's what I'll keep using. Oh, and mine sits in fresh water only, and I haven't had a problem with excessive slime or other such growth.

 

[capta]

Wow, I sure hope none of you take tkanzler's advice. Your bilge pump is your most important installed safety item & breaking the system in any way is just plain foolish. You invalidate your warranty if using Rule pumps if you put in a check valve. DO NOT DO IT.
The exhaust line MUST have the aforementioned loop to prevent back flush & all mine go all the way up to the deck (inside the boat, of course).
It's not a bad idea to carry a portable submersable (3000 gph or so) for emergencies w/ enough hose to get out a port or into the cockpit if the wx won't allow opening a port.
I always Y my main engine cooling intake (before the sea strainer) & have enough hose to reach anywhere on the boat. I've done this when running mega yachts or 40' sportfishing boats. As Murphy's law works perfectly; I've never needed to use the system on any boat I've done it to, but wished I had it on several offshore deliveries, without it.

 

[Ron Wiggins]

Remove the check valve. As others have mentioned, bilge debris can get caught in it and prevent pumping. Even with no debris a check valve can prevent a centrifugal pump from pumping. If the discharge line is full of water and the check valve is shut the pump needs to develop more pressure than the height of water in the discharge line to open the check valve. If the pump casing is not flooded it is trying to pump air. It will never develop enough head to force the check valve open. With no check valve rising bilge water will flood the pump casing and the air will vent out the discharge line. In this condition the pump can develop pressure and force the water out.

Check that the discharge line does not have a loop seal that will trap air in the line. The hose should be continuously sloping up to a high point above the overboard fitting. Having a dip in the line will prevent air from venting out of the pump casing.

 

[racer2677]

Bilge pump runs

I have heard that it's not a good idea to have a check valve in a bilge pump line. Instead, you should probably have the line have a loop above the waterline. This acts as an air gap to prevent siphoning of water into the boat in case you get "pooped". For winter storage, you should disconnect the line from the pump outlet to drain the water out of the line. Also, when the pump shuts off, some water from the drain line will probably drain back into the bilge.

Good luck.

 

[Steve21992]

Bilge Pump Air Lock?

My Bilge Pump is a Rule 500.
I use a non-return valve. (Is that the same as a check valve?) The non-return valve is essential with my configuration. Without it the pump would be emptying the same few liters of water every few seconds.

Once or twice a season I get the same symptoms of having the pump run but not pumping anything. It is almost invariably due to an air lock and usually happens after I have cleaned the intake filter.

I have developed a simple way to clear the airlock.
Disconnect the outlet hose (or even just loosen the clamp around the outlet hose connection). Turn on the pump. It self primes and pumps. While it is running reconnect the hose and tighten the clamp.

Problem solved (at least until next time I clean the filter)

By the way, I replaced the non-return valve this past winter. The original equipment was still in line (1992 Beneteau) and the rubber valve had hardened to the point that it was not closing completely so there was some back flow. However, I do not consider having to replace a valve once in 18 years a bad failure rate. I have replaced the pump itself more frequently than that!

My bilge pump runs, but is not pumping anything out of the bilge. I took it apart this morning to make sure screen was clear and it spun fine-just not taking anything out.

Could the line be clogged? I have a check valve in the line, could this have failed?

I've been told not to have a check valve in the line, but what would prevent the water from just coming back down?

Lets have a vote: yes or no to a check valve.

 

[PBJ]

I run two pumps in my Hunter 31. A small 360 gpm pump does most of the basic clearing via a 3/4 inch hose...:naughty: NO CHECK VALVE. The float switch sits at the same level as the pump. I also run a larger 1500 pump with a 1 1/8 hose for bigger issues. The pump sits right next to the smaller one but the float switch sits about 6 inches higher than the other switch. That way, my smaller, cheaper pump does most of the work but in an emergency, I have a larger volume pump available. And both pumps sit at the same level is I can test either easily. They run on separate electrical circuits through separate bilge pump switches to separate house batteries and discharge on opposite sides of the boat just to be safe. Both lines run directly up to a through valve above the water line and out...no need for any loop as I want that water to have a direct path overboard. If I want a totally dry bilge, I'll soak up the excess water with a sponge.
The two pump system was a lesson learned after my bilge pump and packing gland both failed at the same time. Water was ankle deep in the cabin when I discovered the leak on a very cold night in November with me hand bailing the boat in very cold water!!! If I had the extra pump then, I would have noticed the water was higher than normal but would not have had that sinking feeling! I'm thinking of adding a counter to the larger pump just to know if it did run.

 

[jhnewsome17]

There already been a lot of good advise submitted thanks to your question. It seems that the concensus is to not use a check valve. I am in the process of replacing my bilge pump and was considering adding a check valve. I think I'll forgo that idea thanks to the comments.

I do like the idea of a loop up higher than the through hull discharge. I also believe that you need a seacock valve on every through hull fitting. I was once under tow and had water forced back through the bilge pump line and flooded the inside of the boat.

My bilge pump runs, but is not pumping anything out of the bilge. I took it apart this morning to make sure screen was clear and it spun fine-just not taking anything out.

Could the line be clogged? I have a check valve in the line, could this have failed?

I've been told not to have a check valve in the line, but what would prevent the water from just coming back down?

Lets have a vote: yes or no to a check valve.

 

[Maine Sail]

There already been a lot of good advise submitted thanks to your question. It seems that the concensus is to not use a check valve. I am in the process of replacing my bilge pump and was considering adding a check valve. I think I'll forgo that idea thanks to the comments.

I do like the idea of a loop up higher than the through hull discharge. I also believe that you need a seacock valve on every through hull fitting. I was once under tow and had water forced back through the bilge pump line and flooded the inside of the boat.

If your bilge discharge goes below water under power or sail a simple high loop may not prevent a back siphoning event. You ideally should install a siphon break/vacuum breaker at the highest point, like your engines raw water circuit has, which would break the siphon. Siphons can go up and over things including high points. You ideally want a device that opens and lets air in the line to break the siphon event..

 

[Roger Long]

Wow, I sure hope none of you take tkanzler's advice.

Agreed on the check valve but he does have an excellent suggestion that is very rare and is the way my boat is arranged (That's what makes it excellent).

The bilge pump that works all the time dealing with condensation, stuffing box drips, deck leaks, etc. should be very small with a small diameter line. The low volume of the line will eliminate the backflow cycling problem. This pump will be wet, working often, and will therefore need to be replaced frequently so having it small and relatively inexpensive is nice.

You should then have a big "save the boat" pump (two are better) higher up in the bilge where it and it's float switches stay dry until there is an emergency and are less likely to get clogged with debris.

 

[DannyS]

jhnewsome17,
Maine Sail's right (of course). I had the same issue with our bilge discharge. When under power, ours drops just underwater and would cause the siphon even though we had the loop in the line. I added a vented loop and haven't had an issue since. I would add that the vent on the top of the loop should be cleaned out periodically just to keep it working properly. I can hear the vent sucking air after the pump shuts down which lets me know it's working.