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I've decided to put the bilge pump outlet on the stern (maybe on the transom itself) of my boat but I'm still pondering exactly where. I really like where Tim put it on Glissando, which would work on my boat too because of similar overhangs. My stern however squats when I motor and I could imagine the outlets being in the water potentially creating a siphon problem should the bilge need to drain while motoring. Tim, have you had a problem with this or is that fitting far enough above the water that it's not a concern?
My outlet is submerged when motoring, but I have not personally had a backsiphon problem to date. Other Tritons with their outlets in the same place have had the siphon problem, however. My guess on the difference is that my boat has a shallower bilge--i.e. less head, less hose--than the ones that have had this recurring problem. Either that, or the fact that my bilge pump never runs and therefore is unlikely to start a siphon during these times. Or some combination thereof.
So yes, it's a potential issue for which you should be aware, and for which you should probably take appropriate action. The transom is probably a better place for the outlet, assuming you can endure the aesthetic problems this could cause. But then, sometimes form must follow function.
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My bilge outlet is in the same location as Tim's as well. And yes, on a couple of occasions I have had siphoning problems. I've learned to only activate the bilge pump before or after an outing, when I can make sure it's REMOVING water from the bilge. Haven't had the problem since.
Check valves die, hence making them potentially dangerous in my opinion. The bilge hose that I had the siphon problem with last year had a check valve inline with it. Another owner of a Fuji like mine had his boat sink at the dock and the cause was a bilge siphon that developed when the bilge emptied after he had left the boat. He too had a check valve installed. I personally can't put faith in them.
Like most things, there's seldom a perfect solution, but I'm very happy with our bilge pump arrangement.
Ariel's bilge outlet is located on the port counter, and it's submerged when sailing on starboard tack. A couple of seasons ago the anti-siphon didn't work and allowed sea water to flow into the bilge when the pump shut off. Instead of discovering the problem when I went below and found the sole awash, my bilge pump signal - a cheap buzzer from Radio Shack that I'd wired into the circuit - alerted me to the problem, indicating that the bilge pump was cycling repeatedly. I'm a kind of belt-and-suspenders guy, a firm believer in redundancy without too much complexity. The anti-siphon is good insurance, but the buzzer takes the guesswork out of whether or not the anti-siphon is doing its job. It was a simple addition and has proven to be helpful. In your case, it might be helpful to wire an LED indicator light, mounted in an obvious location, into your bilge circuit since your engine is likely to be running, preventing you from hearing a buzzer.
What about putting a high loop with an anti-syphon valve in it in the bilge pump line? I haven't done this myself, or even seen it done, but given that it's done in head and engine plumbing, I can't see why it wouldn't work for the bilge pump. I can see one problem with it - that it would increase the head that the pump had to work against - but other than that it would seem like a solution which would allow you to put the discharge on the counter, no?
Chris Campbell wrote:What about putting a high loop with an anti-syphon valve in it in the bilge pump line? ?
Vented loops have been use on head systems for ages, should work on a bilge pump as well
Dave Finnegan
builder of Spindrift 9N #521 'Wingë'
-------------------------------------------------------------------------------------------------------------------------------------------------------------------- Gresham’s Law of information: Bad information drives out good. No matter how long ago a correction for a particular error may have appeared in print or online, it never seems to catch up with the ever-widening distribution of the error.
A friend of mine who has a Block Island 40 had the siphon problem and he added a loop above the waterline without a check valve. He drilled a small hole in the top of it so that if the pump was pumping, a small amount of water would spurt out, but it ensured that air was sucked in once the pump stopped pumping whic prevented the siphon. He claims it has served him well for many years and I was considering trying something like it at the end of last year. I ultimately decided to move the outlet. I had a bad siphon experience last year that was exacerbated by a simultaneous failed hose which caused my floor boards to float...NEVER AGAIN! I learned a valuable lesson after that one.
I was doing some reading on bilge pumps this morning and ran across David Gerr's recommendation in his book "Boat Mechanical Systems Handbook" that a vented loop was needed in a bilge pump installation where the discharge was lower than the water line under any conditions (such as when the boat is heeled). He has an illistration showing the correct way to install it so even if the boat is heeled 35 degrees the vented loop is still above the waterline.
I was also reading information on the Rule website for their bilge pumps and they recommend against a check valve.
I was under the impression that vented loops contained a one-way valve for the air to pass through. I imagine it's possible for that one-way air valve to fail thereby allowing the siphon to occur. I have a vented loop on my head setup and now wonder if there is any maintenance involved with them to prevent failures? I have never touched it since I took ownership of the boat.
I do like my friend's setup on his BI40 because there is no valve involved. He does however as a consequence have water spurt out when the bilge pump is in use and can imagine debris from the bilge plugging that hole. There's never an easy answer in my mind and that's why I'm going high transom for the outlet.
