Corrugated hose or smooth for bilge pumps?

[thinwater]

Originally Posted by CarinaPDX

There does seem to be a lot of hostility towards check valves here. There are good reasons for having them in a bilge pump system, especially for maintaining prime. I have two 1-1/2" manual diaphragm bilge pumps, each with its own pickup which includes a foot valve. The foot valve is a joker valve, the same as in the output of the manual bilge pumps and just as reliable. My cockpit pump is 6'-7' above the pickup, so takes some doing to create enough vacuum to draw the water up to the pump initially; having it primed is an advantage. Also, after pumping and without the foot valve the hose empties back into the bilge, undoing some work. Presumably the electric pump(s) is turned off, or otherwise it will be restarted by the rise in bilge level at the sensor. My electric pumps are submersible, so I have a valve right after the output - otherwise the contents of the hose from about 8' up drains back into the bilge and restarts the pump causing unnecessary cycling.

Most boats probably don't have the high lift that I do, or even the large hoses I use with the main electric pump, so back-draining and loss of prime are less of an issue. YMMV - I just note that blanket condemnations are often not appropriate.

Greg

Not hostile.

Note that one of my reasons--ice formation--is lethal in freezing climates and irrelevant in warm climates. I've seen it sink boats, and the OP is in the north country. For him, it is a very serious consideration.

[billknny]

Originally Posted by CarinaPDX

There does seem to be a lot of hostility towards check valves here.....

I just note that blanket condemnations are often not appropriate.

Greg

Actually, blanket condemnation of check valves IS appropriate.

I worked in the chemical industry for many years. In design reviews the safety people would ask "What happens if we have reverse flow in this pipe?" if the answer was "Something bad" a check valve was NEVER EVER allowed as a solution. They FAIL. All of them. Eventually. And if they fail, they give NO external notice that they have failed. Until bad stuff happens.

If your bilge pumping system REQUIRES a check valve it is a crappy design. Period. Full stop. Fix it.

Remember... all check valves WILL fail. And you will not know they fail until whatever they are supposed to prevent happening, happens.

[CarinaPDX]

Originally Posted by thinwater

Not hostile.

I didn't mean to refer to you, or even personal hostility - we have covered this elsewhere and there have been numerous comments warning against check valves in a very absolutist way. As always for any piece of equipment one should know why it is needed, which design is most appropriate for the application, how to maintain it and use it properly.


Freezing is a concern for all hoses with water in them, in the right weather. Around here it is rarely an issue - until it is, and hoses freeze, split, thaw, then sink the boat. For this application a split hose would compromise the bilge pump function but nothing else - the hose goes up to the deck before turning down to an outlet well above the waterline. There is a good argument for buying seacocks with a drain plug just inside the valve, and even for the valve chamber itself, to prevent ice forming.


Greg

[foufou]

Forgot to mention that the frozen check valves were brass house plumbing types. But the kind doesn't matter. They are unnecessary and better replaced by high loops. Those work.

[CarinaPDX]

Originally Posted by foufou

Forgot to mention that the frozen check valves were brass house plumbing types. But the kind doesn't matter. They are unnecessary and better replaced by high loops. Those work.

Clearly the kind does matter, because reliability matters - the brass parts are pretty much guaranteed to seize when used in salt water. The rubber joker valves I have used successfully didn't fail in 30 years, either in the foot valves or the outlet of the bilge pumps.

The idea of not using high loops and relying on check valves INSTEAD to prevent backflow is, of course, unsafe. That is just the wrong application for a check valve. Using them to hold prime and prevent unnecessary cycling is a perfect application. Same check valve (well, assuming not brass ) in a different application within the bilge pump system makes a lot of sense.

Greg

[Exile]

When I purchased my now 32-year old boat 11 years ago, it had a Rule centrifugal primary bulge pump with the type of check valve that has the rubber flap. It was working fine back then but I replaced it with the same type, and recently replaced it again, still working fine. It's called a Bosworth (see pic below) but I believe Jabsco makes a similar one.

With a pretty large CC boat I have about a 16' run to the transom outlet, and probably about 4' of total lift. The pump sits in a deep, narrow part of the bilge, and given the long, steep run to the outlet, my 1 1/8" diameter hose holds a lot of water between pump & outlet. Without this check valve, the pump cycles every few seconds, and would continue to do so for a very long time if no check valve were in place. I do have a large loop at the outlet with a Forespar siphon break, but my understanding is that this is to prevent seawater entering the hose from the transom, and does nothing to hold the water in the hose from running downhill back into the bilge.

Those who are absolutist about not having check valves are in good company, however. In other threads Maine Sail has recommended a second diaphragm pump for the "nuisance" water that drains back into the bilge after the primary cycles. Other than fitment, etc. issues, my concern about such a set-up is that a centrifugal pump requires priming, so if it is sitting in a dry bilge it may cavitate rather than pump water out of the boat. I could go with a diaphragm pump as my primary I suppose, with an intake hose that sits down in the bilge while the pump stays high & dry. But after 11 years of flawless duty from both the check valve and a couple of Rule 2000's, I'm not sure I need to make any changes.

I remain open-minded for any better/safer solutions, however, and understand why the ABYC and most experts seem to frown on any sort of check valve.

[Exile]

Bosworth check valve:

[foufou]

Good point about the obvious mistake of having brass check valves in salt water. The reason for saying the type of valve didn't matter is that the bilge pumps I have bought have the duck bill valves built-in. No need for an external one

[mitiempo]

Originally Posted by billknny

Actually, blanket condemnation of check valves IS appropriate.

I worked in the chemical industry for many years. In design reviews the safety people would ask "What happens if we have reverse flow in this pipe?" if the answer was "Something bad" a check valve was NEVER EVER allowed as a solution. They FAIL. All of them. Eventually. And if they fail, they give NO external notice that they have failed. Until bad stuff happens.

If your bilge pumping system REQUIRES a check valve it is a crappy design. Period. Full stop. Fix it.

Remember... all check valves WILL fail. And you will not know they fail until whatever they are supposed to prevent happening, happens.

In my opinion there should be 2 electric pumps. One at the lowest point of the bilge with a check valve (Bosworth or Jabsco type) so no water drains back. This is the maintenance pump that is used most often and leaves an almost totally dry bilge. It can be a small capacity pump or not. The other pump is high capacity and installed a bit higher than the first pump. It should not have a check valve. It will only come on if the water exceeds the level of the first pump. Smooth bore hoses on both pumps as well as an anti-siphon installed in a high loop under the deck. On a sailboat the best location for the outlets is the transom so heeling has no effect. Each pump should have its own dedicated outlet.

Bilge pumps do not REQUIRE a check valve but it sure keeps the bilge dryer, especially on a shallow bilge modern boat.

[Exile]

Originally Posted by mitiempo

In my opinion there should be 2 electric pumps. One at the lowest point of the bilge with a check valve (Bosworth or Jabsco type) so no water drains back. This is the maintenance pump that is used most often and leaves an almost totally dry bilge. It can be a small capacity pump or not. The other pump is high capacity and installed a bit higher than the first pump. It should not have a check valve. It will only come on if the water exceeds the level of the first pump. Smooth bore hoses on both pumps as well as an anti-siphon installed in a high loop under the deck. On a sailboat the best location for the outlets is the transom so heeling has no effect. Each pump should have its own dedicated outlet.

Bilge pumps do not REQUIRE a check valve but it sure keeps the bilge dryer, especially on a shallow bilge modern boat.

That almost exactly describes the set-up I inherited and what I have opted to maintain. I see the potential for even the rubber Bosworth-type valve getting stuck closed from debris, so it is in an accessible spot where I can periodically inspect it. One time I had the siphon loop at the transom get blocked from debris & prevent flow, and I recently discovered that there's a small joker valve in the fitting for the siphon break that had worn, causing water to leak out. So whatever system you have, it's important to keep your bilges as clean as possible.

[Cheechako]

Almost sank my boat by installing a check valve. instead of a big loop over the outlet (which was above the waterline) I put the check valve in with new hose. Sailing shortly after that I just felt like the boat was sluggish. I lifted a floor board and the bilge was full and water was just starting to touch the floor underside!
BTW, those grey plastic check valves restrict the flow a lot, possibly 50% . They are not designed with room for the flap to entirely open but rather just bend up partially.

[Exile]

Originally Posted by Cheechako

Almost sank my boat by installing a check valve. instead of a big loop over the outlet (which was above the waterline) I put the check valve in with new hose. Sailing shortly after that I just felt like the boat was sluggish. I lifted a floor board and the bilge was full and water was just starting to touch the floor underside!
BTW, those grey plastic check valves restrict the flow a lot, possibly 50% . They are not designed with room for the flap to entirely open but rather just bend up partially.

What type of check valve did you install? Was it the all-metal/brass kind?

You are no doubt correct about flow-impedance with the Bosworth-type with the rubber flap. One reason it should probably be installed only on the "maintenance" pump and not on the backup.

With such a long, steep run from my bilge to the transom outlet, I'm just not sure what a reasonable alternative might be. Maybe a diaphragm pump that sits high & dry with the intake hose that sits down in the bilge. I don't think they have as much capacity, but that doesn't really matter for more of a maintenance function. I also like the idea that you can see the thing. The submersible ones like the Rule's are all too easy to forget about. I also don't think the diaphragm types require priming, so you could potentially keep almost all the water out of your bilge under normal circumstances.

[Terra Nova]

Originally Posted by CarinaPDX

...check valves...There are good reasons for having them in a bilge pump system...

Complete BS.

NEVER install check valves in bilge pump lines.

[Cheechako]

Originally Posted by Exile

What type of check valve did you install? Was it the all-metal/brass kind?

You are no doubt correct about flow-impedance with the Bosworth-type with the rubber flap. One reason it should probably be installed only on the "maintenance" pump and not on the backup.

With such a long, steep run from my bilge to the transom outlet, I'm just not sure what a reasonable alternative might be. Maybe a diaphragm pump that sits high & dry with the intake hose that sits down in the bilge. I don't think they have as much capacity, but that doesn't really matter for more of a maintenance function. I also like the idea that you can see the thing. The submersible ones like the Rule's are all too easy to forget about. I also don't think the diaphragm types require priming, so you could potentially keep almost all the water out of your bilge under normal circumstances.

It was a bronze flapper valve and it was installed in a horizontal run so gravity wouldnt effect it much.

[Exile]

Originally Posted by Cheechako

It was a bronze flapper valve and it was installed in a horizontal run so gravity wouldnt effect it much.

OK, that makes sense. I have a couple of those installed vertically in gravity-fed sink drains and I periodically need to tap on them with a hammer to free them up. Then they work again for awhile. They're only there to keep saltwater from splashing up into the sinks under heel, so not exactly mission critical. When they do stick, they stick in the closed position (like in your case) so freshwater from the sink cannot drain. Probably not advisable in a bilge pump application, even if installed vertically.