I sail a Pearson 28. The bulge sump is about 18 inches aft of the mast. The bilge has five compartments with limber holes between them. The electric bilge pump is located in the deepest compartment and the strum box for the manual pump is located in the compartment just aft of the deepest sump. The manual pump is a gusher 400 (?) and is mounted at the aft end of the cockpit with 1" hose and exhausts thru a "Y" fitting and then to a stern mounted thru hull (1 & 1/8 inch).
The electric pump feeds a 1&1/8" hose to the same "Y" about one foot from the thru-hull. My problem is that both of these hoses are about 20 feet long and when you stop pumping more that 3 gallons of water returns to the bilge.
So, how would you recommend re-plumbing these two bulge pumps to reduce the back flow? And what would you replace the manual pump with (it's pretty old now and finding rebuild kits is difficult)?
Install a diaphragm "nuisance pump" to deal with nuisance water and let the Gusher and centrifugal pump deal with Oh $hit
That depends on the type of check valve, large flap and wieghted ball generally have full flow and rarely fail closed they can fail open, small springed ones are only good for clear liquid and higher pressure. At least that is what I've seen.
Where did you come up with this info???? It is contrary to the many, many, many check valves I have seen stick closed, and some of them actually sank boats or at the very least murdered battery banks....
"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 can't feel the weight of the water, and shuts off, allowing the bilge to fill with water!"
Rule does not recommend a check valve on their centrifugal pumps. You can do what you want on your boat but you would be ignoring the advice of the manufacturer of the pump, and creating a potential safety issue. The first rule of bilge pump system design is to design a good system
not Band-Aid a bad one.
Just because DIY's and builders do it, to save money
, does not make it a correct
The prudent installation on a sailboat, where you want to prevent flow-back, is either to install a diaphragm pump, the ideal solution, or to get a float switch with a delay or install a smaller "nuisance pump". The delay will not always solve the problem however so a diaphragm pump that can handle a check valve, or has the check valve feature built in, is the proper & safe solution to flow-back.
A check valve in a centrifugal pump is not a solution, it is a potentially dangerous installation.
If you want to solve the problem the right way
then you'll want to install a diaphragm pump. If you want to go against the sage advice of the manufacturer buy a check valve....
Other than what I posted above.. Here is one of the responses Rule sends out when you ask this question. This was sent to one of my customers who chose not to believe me. He then got really angry when his cabin sole was ruined and tried to blame it on Rule sending them a rather terse letter... I had already warned him not to install the check valve but he knew better.. Cost him nearly 4k for a new cabin sole...
Rule Pumps Tech Support said:
Both Rule and our competitors' centrifugal style bilge pumps have very little air vacuum pressure because there is a large gap between the centrifugal impeller and the impeller housing (depending on the pump, it could range between 1/16"-3/16") which allows high flow and some bilge debris to flow past the impeller without damaging the unit.
The negative side of having the large gap between the housing and the impeller is the impeller needs to come in contact with water to pull the water out of the bilge (water being a lot thicker than air).
A check valve in the bilge hose seals air in the hose and will not allow the water to come in contact with the impeller. The pump may be in a few inches of water (or completely submerged) but because of the air pocket, the pump cannot remove the water from the bilge.
If you wanted to remove as much water as possible, you could try installing a diaphragm style pump. The diaphragm pumps have internal check valves and are self priming to at least 6'. The only drawback is that the diaphragm pumps do not have as much flow as the centrifugal pumps. If you mounted the centrifugal pump switch higher than the switch for the diaphragm pump, the diaphragm pump could be used for the daily water seepage and the centrifugal pump could be used for emergency pumping.
In that last sentence Rule nails it.... That is a "proper" bilge pumping system which has no check valve in the centrifugal pump discharge....
If you want to prevent back-flow use a two pump system a "nuisance pump" (diaphragm) and a "emergency" pump (Centrifugal). If I had a dime for every bank of batteries a stuck check valve has murdered on a centrifugal pump......................
I would never
, and I don't use the word never
very often, recommend a check valve on a single centrifugal pump installation.
If you want a check valve please use a rotary vane or diaphragm pump that has the ability to deal with the head pressure of the standing water and to push open a sticky check valve. Most small boats can't swing the loads of a rotary vane pump so a diaphragm pump is the way to go.
Centrifugal pumps with check valves often just make neat little bubbles and the water remains in the bilge. Seen this far too many times to count and the damaged or sunk boats that go along with it..
It is your boat, you can do as you wish, but check valves on centrifugal pumps are a danger waiting to happen. You would be horrified at the number of "check valves" I see that fail to open. Beyond that most leak back within a few months causing lots of wear & tear on the pump and battery bank.
I am the guy replacing the batteries that the bilge pump killed when the check valve stuck and the float switch remained ON.........
You can design a bilge pump system safely
or choose not to....