another bilge pump question

[John T1594]

Keep the check valve

I have been using a check valve for years because of the back flow issue. If you keep your bilge clean, you should not have a problem.
There can, however, be a problem with air-lock so that the pump runs but will not pump water out of the bilge, You could drill a small hole in the outflow tube before the check valve, but I have a better solution. Keep the hose very short between the pump and the check valve. That has solved my problem and eliminated the air lock.

 

[J Hunter]

I have a small deep bilge that short cycles my pump when I had it mounted right in the bottom of the bilge. I was usually pretty successful at keeping the bilge very dry, but for two years now I've contended with small leaks both from the deck and stuffing box. I didn't like any of the solutions: check valve, second pump etc. Last summer I took a flat strip of stainless and drilled 2 big holes in it and got two extra keel bolt nuts to suspend my pump about 2-3 inches above the bilge bottom. This worked great for the rest of the summer last year and I'm going with it again this year. My bilge widens out enough a little above the bottom so that the backwash doesn't anywhere near close the float switch. Has anyone ever tried to make or buy some sort of two position float switch that made at a higher level than it opened at? Either with two actual internal different level switches and some kind of built in relay or solid state logic or maybe some kind of delay on open timer or even a mechanical damper that kept the float above the water level for extra time on a drop in level?

The problem is solved in a number of ways in shoreside sump pump switches. Sometimes with two separate actual switches with the high level turning the pump on but then a low one having to open to turn the pump off. I've also seen the type where the float is not attached directly to the switch arm, but slides vertically up and down the switch arm rod within an adjustable range. It has to float all the way up to the top stop nut before it lifts the rod and makes the switch which must have some kind of detent once it's in the on position because as the pump empties the sump the float slides back down switch rod but doesn't turn the pump off until it's full weight is on the bottom stop nut and pushes down on the rod and opens the switch.

The other type I've seen (and these work in sewage so a dirty bilge wouldn't seem like too much of a dirty environment challenge) are the ones where the switch is actually in the float which is just floating around loosely in the sump at the end of the wire whip that attaches it to the pump. These switches open and close based on the angle of the oblong shaped float: it's closed when the end the wire whip comes out of gets dragged lower than the free end when the sump fills and the wire whip pulls down that end, but it doesn't open until the free end of the float dangles lower then the end with the wire whip coming out of it.

The general idea being the pump gets automatically turned on at a level incrementally higher than it automatically shuts itself off at, preventing short cycling. Does anyone know of an automatic bilge pump float switch that's designed to work something like this?

 

[petersea]

OK here is my take on this...... I have had both check value and no check valve ( same as no return valve) depending on the boat.. The small but deep bilges are a perfect example of needing one. As in the hunter 340 as ktanzler has. (I had one in my 336 almost same boat) If possible I would not have one but in certain circumstance they are needed. They need to become part of a regular maintenance program to check and clean as needed. I also vented mine as a precaution (small hole on exit side of valve so as not to have the pressure issue to deal with. I had no problems with it and the current owner has not had any problems either .I did make sure he knew of the check value and was aware it needed to be cleaned and checked. Most shower sump tanks have a manufacture installed valve to prevent back-flow and most bilge pump manufacturers make check valves also, so go figure. The manufactures recognizes the need. if your boat needs one install it and maintain it. If it does not need one don't install that simple. I know that I may be in the minority opinion but until you have listened to your bilge put cycle 10 to 12 times because of back-flow you won't understand the need. I could never be comfortable knowing how many times the pump would cycle off and on because of it. If a person really wanted to have a great bilge pump system go with the small pump (with or without a check value) and then larger pump as suggested earlier by PBJ with the addition of a high water alarm so that your marina neighbors know there is a problem. Just my two cents worth .......

 

[jimford2158]

I have a small 12 volt bilge pump in the very bottom that has a 1/2 inch hose and no check valve. I also have a large 110 volt pump that sits higher up and uses 1 1/4 inch hose and has a check valve, it uses load sensing and runs off the invertor when sailing. The small pump has an electronic moisture sensor which works very well. Occasionally I will clean the bilge area, which is less than 2 cubic foot, with a wet vac to remove any debris and then flush both systems with 5 gallons of fresh tap water too verify operation. Usually don't get too much water in the boat since I plugged all the above waterline leaks(fill fittings, scuppers, hoses and an uncovered hole thru the windlass). I also have a manual bilge pump with 1.5 inch hose, which is required by the Coast Guard. All of the hoses discharge just below the gunwhale and are on the entry side next to the dock so if a problem exists it will get noticed sooner. All of the hoses and the pumps have been recently replaced.

 

[J Hunter]

I see a bit of a problem with the idea of a large pump acting as back up for a smaller pump. The back up, by definition is the more critical piece of equipment. If it fails, or runs until available power is exhausted, the water rises in the hull and keel descends without further action. If the lower level actuated pump is sized to generally accepted practices, then the pumping required to keep the vessel afloat upon it's failure would in the vast majority of cases be no more than that capacity. If the idea is to activate the backup only after a higher than typical amount of water is entering the vessel (an amount that the primary pump would not be sized to remove) than the control system has the flaw that the most critical pump gets no regular use or testing and is for that reason much less reliable than the one designed to simply keep a small puddle out of the bilge. I do like the idea of a second 120v pump that works straight off of shore power when your at the dock, but I'm on a mooring.

 

[CEOmike]

Loops with siphon valves need maintanance and can fail to work (ie a leaf that gets sucked in and blocks the hole) Check values can only get jammed with debris from the bilge that has passed throught the pump, an unlikely and controllable event compared to a leaf)

Pumps wear out, a pump that works without a check value but not with is more likely just worn out. Replacing the impeller is sometimes effective but is a "cheap" job that may or may not work. Check values rarely fail in comparison to wear of a pump. Replace the pump and the check value because the value is cheap insurance.

Anything else may or may not work depending on the situation and is asking for trouble.

 

[SeaTR]

Peoples,
Thanks a grunch for the information / experience sharing on this topic !! I've had some problems with my "small leak pump" setup and you've directly answered some questions, e.g., to check valve or not, siphon loop efficacy, 2 pump setup advantages, to name a few...

Enjoy the 4th weekend,
10Q,

SeaTR