# Urgent Issue: Bilge/Anti-Siphon



## labatt (Jul 31, 2006)

So last night our bilge pump started going on every thirty seconds. We looked and there was a continuous stream of salt water entering our bilge. We spent 3 hours ripping apart our boat and it mysteriously stopped. 

This morning it started again, and we pulled apart the boat and this is what we found. The bilge pump goes to a 5' hose, then to a check valve, then to a loop well above water level, then back down below waterline to a non-closable through-hull. On the top of the loop there is a 1/4" hose that leads right back to our bilge, below waterline. The water is coming through the vent hose that leads back to our bilge.

I'm assuming that at some point there was a standard air vent on the top of the vented loop. Perhaps when the boat was heeling and the rail was in the water, the vent spurted water, so someone put a hose on it to drain it to the bilge. It looks like our check-valve needs replacing too. At this point, it looks like we're creating a siphon at random times as opposed to breaking it.

Based on what you've read here, what are your thoughts on the proper way to have the bilge line hooked up? We're still taking water in and need to replace it ASAP.


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## Cruisingdad (Jul 21, 2006)

Catalina uses a very similar system. As the original system was designed, it sounds like the right system to me. Obviously, you want to replace the check valve and fix the loop if it has been gerry rigged They are renound for getting stopped up and failing - especially after a rough ride when things start breaking lookse or running free in the bilge. However, they are useful and most of the larger Catalinas put them on. It is of interest to note that many higher-end builders do not.

I would say fix what you have right now. Carry a spare check-valve. Do you also have a highwater alarm? You could rig it fairly easily into your system and add another bilge pump into that so that it adds another level of safety. We will not go back to sea without one.

Did that help? Shoot pics and post here. 

Brian


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## sailingdog (Mar 19, 2006)

*If the bilge pump exits via a below-the-waterline through-hull, it needs a seacock on it. If that hose ruptures, you're basically RTF...* That would be the first thing I'd recommend doing. Replacing the siphon break would be the second. Don't use a check valve, they're just a RPITA and can cause some serious problems in a bilge pump output line.


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## JohnRPollard (Mar 26, 2007)

Something similar happened to us a few years ago. It is initially disconcerting while you try to locate the source of the water.

I agree, there should be a seacock on that thru-hull. Ours is nominally above the waterline (just), and it has a true seacock on it. So we were able to simply open/close it manually until we fixed the ant-siphon vent. 

What happens is that when you load up a boat for cruising, that thru-hull can easily end-up below the waterline, which makes it more vulnerable to back-siphon if there's a problem with the siphon break.

I don't know about the hose contraption leading back to the bilge, but I don't think it's the ultimate source of the problem. 

Clean/repair or simply replace the anti-siphon loop. They can get crusted up with salt residue. Right now it is sticking, and causing that vent line to create a siphon back to the bilge.


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## Cruisingdad (Jul 21, 2006)

I respectfully dissagree with Dog on that one. I respect what he say, but I dissagree here. I believe a checkvalve is a good system, but requires maintenance and requirs you to carry a replace. Generally you can clean/repair these yourself. Don't give up on theis one yet. At the bery least, you might be able to use it as a spare. 

Catalina does not put a valve on the output of the bilge either. I guess the point is that if you are getting water coming through while on a tack, you would fall off and fix the issues. The siphon break is supposed to handle the backflow - not the check valve. THe check valve is to keep the water between the two to keep from flowing back into the bilge. It serves a good purpose. It could be argued that the check valve is a backup system... though that is not its intention.

By the way, is your siphon break centerline? Where is it on the boat?

Brian


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## Calabego (Nov 4, 2008)

I have no knowledge of the Passport 40 but...
Shouldn't that system have a seacock below the waterline?
Provided you have the appropriate sized bungs, replacing (or even repairing depending on where you are moored) the check valve and getting a seacock on that throughhull wouldn't be difficult.

Having a bung or two handy would priority 1 in case that check valve gets stuck full open.

[edit]
Oops, looks like several beat me to the punch. Glad I was on the same wavelength.


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## Cruisingdad (Jul 21, 2006)

I missread his post. I did not realize that the bilge pump exited below the waterline. I agree with Dog on that. Ours exits well above the waterline.

- CD


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## Maine Sail (Jan 6, 2003)

Cruisingdad said:


> I respectfully dissagree with Dog on that one. I respect what he say, but I dissagree here. I believe a checkvalve is a good system, but requires maintenance and requirs you to carry a replace. Generally you can clean/repair these yourself. Don't give up on theis one yet. At the bery least, you might be able to use it as a spare.
> 
> THe check valve is to keep the water between the two to keep from flowing back into the bilge. It serves a good purpose. It could be argued that the check valve is a backup system... though that is not its intention.
> 
> ...


I'll also agree that check valves are bad news. Centrifugal pumps have very little ability to overcome head pressure. 15' of 1" hose that goes to a point 6' above the level of the pump will and can often create a cavitating bilge pump that does nothing but make bubbles in the blige because it can't overcome the head pressure of the water in the hose.

Many moons ago, when I worked in boat yards, we yanked check valves all the time. A customer would come in complaining that the pump was running but the bilge would not drain and instead would just kill the battery. 30 seconds later armed with only a screw driver the check valve was gone and the bilge pump working.

If you don't like the drain back then invest the $1.39 on a turkey baster. Check valves are a safety problem and I have seen it more times than I can count. Even in brand new installations I have seen pumps cavitate against the head pressure of the static water stuck in the bilge line...

If you use a high head capacity diaphragm pump go ahead and use a check valve but if you have a centrifugal pump (Rule type) throw it away and get a turkey baster or sponge.

I personally do not like any bilge pump exiting below the static waterline as it's accepted safe practice that all seacocks should be closed when one leaves the boat unattended. closing the bilge pump seacock defeats the purpose of having a bilge pump..?

The ABYC build standard and before that, USCG advice, has been that any below waterline fitting requires a seacock that can be shut. In the most recent iteration of ABYC H-27 they loosened up the the rules around seacocks being installed to max heeled waterline. You no longer need to install a seacock above the static waterline to be ABYC compliant, though it is advised as good practice, but you always need one for below water applications..


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## labatt (Jul 31, 2006)

OK... let's forget about the seacock - I already know I need to put one in at the next haul. Let's also forget about the check valve. I'm more interested in figuring out what I should do with that vent hose that runs below the waterline to our bilge and is siphoning the water - I need to fix that before anything else. I'm thinking of yanking it off, but then I'm concerned about water getting into the cabinet where the loop is.


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## JohnRPollard (Mar 26, 2007)

labatt said:


> OK... let's forget about the seacock - I already know I need to put one in at the next haul. Let's also forget about the check valve. I'm more interested in figuring out what I should do with that vent hose that runs below the waterline to our bilge and is siphoning the water - I need to fix that before anything else. I'm thinking of yanking it off, but then I'm concerned about water getting into the cabinet where the loop is.


Labatt,

I guess I did not make it clear above, but the problem is not this line. The problem is with the vented loop ant-siphon valve. It is likely gunked up with crud and is sticking. Take it off, clean it up, and put it back in place as it was. Or replace it with a new one. That should solve the immediate problem and you can worry about a seacock down the road.


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## danielgoldberg (Feb 9, 2008)

*Try this*

Remove the 1/4" vent hose from the vented loop, and see if the backflow stops. If so, it most likely means that your vented loop was clogged somewhere (or maybe the hose was resting in the bilge at a point lower than the through hull), so you created a siphon. Removing the hose and reintroducing the air break broke the siphon, if this works. If so, then clean out the vented loop and you should be fine. But, be careful about how you re-lead the 1/4" vent line, and frankly, I would consider leaving it off, or possibly leading it to somewhere much higher so that you still get air into the system, but ensure that the end of that hose does not end up lower than the through hull.

Regardless, get a valve on that through hull. That's no joke. I am quite surprised to hear that there is a below-the-waterline through hull with no valve. What is that boat, a Beneteau or something?


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## AE28 (Jun 20, 2008)

*Maine Sail...*

Is a check valve the same as an anti siphon valve?
Thanks,
Paul


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## Maine Sail (Jan 6, 2003)

labatt said:


> OK... let's forget about the seacock - I already know I need to put one in at the next haul. Let's also forget about the check valve. I'm more interested in figuring out what I should do with that vent hose that runs below the waterline to our bilge and is siphoning the water - I need to fix that before anything else. I'm thinking of yanking it off, but then I'm concerned about water getting into the cabinet where the loop is.


Either install a new siphon break (it should not need a drain hose) or clean the old one & fix it out or, as a band-aid measure, directly vent that hose to the exterior of the boat preferably high enough to break a siphon..

If it were me I'd be drilling a new hole in the boat to drain the bilge pump overboard, above static waterline, and preferably above heeled waterline like on the transom somewhere.


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## Maine Sail (Jan 6, 2003)

AE28 said:


> Is a check valve the same as an anti siphon valve?
> Thanks,
> Paul


No a check valve is a device that only allows water to flow in one direction. Sometimes they use a spring loaded ball and other times they use a cheap rubber flapper which often becomes gunked up with bilge crap and likes to stick closed or not close and eventually allow all the water to trickle back to the bilge anyway.

An anti-siphon or vented loop device can have water flow either way through it but works on pressure/negative pressure. When the hose has pressure from a pump it closes a little valve to prevent water squirting out the top. When the pump shuts off the water naturally wants to settle and the valve allows this by opening on suction or negative pressure and allowing air to take the place of the water. You can't complete a siphon without water and a siphon break allows air into the top of the loop...

Anti-Siphon device:
Courtesy: Engines1, WESTERBEKE, ENERGY1, UNIVERSAL, FUEL POLISHING, MARINE ENGINES, MARINE PARTS, ALGAE-X


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## eherlihy (Jan 2, 2007)

Labatt,

I've been reading your blog. You're a lucky guy to have a wife and kids that support your dream. Also lucky that you have a business that you can leave in other people's hands while you're away...

Remember from your blog that the boat is now sitting 2(+) inches lower than it had before you moved aboard? My bet is that the end of the anti-siphon loop (the 1/4" tube) is now below the waterline because of all the new equipment (and weight) that you have on board. I suggest that you trim the 1/4" tube so that it ends 3" above where it currently does, yet still empties into the bilge.

A quick test would be to remove the 1/4" tube at the top (near the cabinet) to ensure hat the siphon is broken first. Spend an extra night where you are (on a mooring). If the pump does not start, this must have broken the siphon. The next morning, I would then cut the 1/4" tube.

- Ed


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## eherlihy (Jan 2, 2007)

... Oh yea, 

Put a seacock on the line from the bilge pump ASAP!!!!!


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## danielgoldberg (Feb 9, 2008)

labatt said:


> I'm thinking of yanking it off, but then I'm concerned about water getting into the cabinet where the loop is.


Assuming the vented loop itself is "above" the through hull, there is no reason at all that water should flow out into the cabinet. But just in case, get a small bucket or large glass, or whatever will fit into the cabinet, and put that underneath the vented loop while you're removing the vent hose, and then very carefully remove the vent hose in such a way that you can put it right back on if you get a gieser (sp?). Note that because the entire assemply already is filled with water due to the siphon, you may very well get some water coming out initially, but as soon as you break the siphon, the water should recede back down the hose on either side of the vented loop towards the through hull and bilge pump, respectively.

This is hard to describe verbally, so if it's not clear, my apologies.


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## btrayfors (Aug 25, 2006)

Maine Sail said:


> ....
> 
> If it were me I'd be drilling a new hole in the boat to drain the bilge pump overboard, above static waterline, and preferably above heeled waterline like on the transom somewhere.


Maine Sail has it right!

Bilge pump discharges belong above the waterline. Way above the waterline. Preferably on the transom where they'll stay above the waterline when heeled.

I'd be putting in a new discharge thru-hull, with an appropriate shutoff valve, and no one-way flapper valve, vented loop, or other obstruction to restrict the flow and/or create back pressure or require watching/maintenance.

JMO,

Bill


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## sailingdog (Mar 19, 2006)

Ideally, the new through-hull for the bilge pump should be six or more inches above the waterline. IIRC, ABYC doesn't require seacocks for through-hulls more than six inches above the waterline.


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## xort (Aug 4, 2006)

Regarding syphon loops, take a look here please...

Hints and Projects


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## danielgoldberg (Feb 9, 2008)

*Labatt??!!*

Are you there? Did you sink? Did you fix the problem? How did it play out?


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## Cruisingdad (Jul 21, 2006)

danielgoldberg said:


> Are you there? Did you sink? Did you fix the problem? How did it play out?


I was wondering the same thing. Let us know how you're doing.

Brian


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## labatt (Jul 31, 2006)

Alright - after 12 hours of wrangling we finally gained access to the vented loop. It was behind some very "fitted" pieces of wood. Once we got the loop off we found that the anti-siphon valve was completely shot (hole right through it). We're not taking any water in right now, but at the same time, the bilge pump is disconnected until we get a new vented loop. We use the shower sump as a secondary pump but it's 18" higher than the bilge, so there's got to be a lot of water on the boat before it triggers. We also have the manual pump. Hopefully I'll be able to find a place to get a 1" vented loop tomorrow. West doesn't have it in stock, and I hate to wait all the way over the weekend before we get it hooked back up.


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## danielgoldberg (Feb 9, 2008)

labatt said:


> Alright - after 12 hours of wrangling we finally gained access to the vented loop. It was behind some very "fitted" pieces of wood. Once we got the loop off we found that the anti-siphon valve was completely shot (hole right through it). We're not taking any water in right now, but at the same time, the bilge pump is disconnected until we get a new vented loop. We use the shower sump as a secondary pump but it's 18" higher than the bilge, so there's got to be a lot of water on the boat before it triggers. We also have the manual pump. Hopefully I'll be able to find a place to get a 1" vented loop tomorrow. West doesn't have it in stock, and I hate to wait all the way over the weekend before we get it hooked back up.


Do you have any plumbing supplies on the boat? Or can you get to West easy enough? Here's a very temporary fix (it probably could last a long time, but I wouldn't leave it to that):

Install a check valve in the portion of the hose after the vented loop on its way to the through hull. The lower you can put the valve the better, but I know you are going to have an issue with that because you don't have a valve on the through hull, so you need to be sure you are above the waterline. In truth, this likely would work if you install the check valve just after the vented loop, but it really would be preferable to have the valve farther down so that gravity works for you a bit.

The reason this works is that the check valve will prevent the water from coming back up into the boat, even if you otherwise would have a siphon effect (the check valve blocks the water, but it also interrupts the siphon). The other thing is that having the valve on the way "down," so to speak, avoids the problem others have mentioned of the bilge pump not having enough oomph to push the water through the valve (because once past the vented loop, gravity takes over and the water should push the valve open with no trouble on its way to the through hull). Of course, if the check valve gets stuck open, then it doesn't work, which is why I would call this a temporary fix, but it ought to get you through the weekend.

It's also important to get the right kind of check valve. If you get one that just has a metal flapper, it won't work because the flapper will lay open with the valve installed vertically, and you need the valve installed vertically for this to work. The black pastic valves actually are preferable for this application (something more akin to a joker valve). If in doubt, take the valve, hold it vertically in your hand, and blow "up" into the valve; if you can feel the breeze coming out of the top of the valve while holding it vertically, it's not the right kind of check valve.

Let me know if this isn't clear, and I can try to describe it better, or we can even talk on the phone for a few minutes if necessary.

By the way, did you try disconnecting the vent hose to see if that alone broke the siphon? I would think that should work, even with a screwy vented loop. And note that provided you don't have leaks giving a constant stream of water into the bilge, I wouldn't worry too much, temporarily, about pumping water into the cabinet when the bilge pump goes on (because it shouldn't go on if you're not filling your bilge).

And yet another thought, take the vent house, pull it out of the bilge, and shove it up into the space where the vented loop is located, coiling the vent hose. That should allow air in, the lack of which is your problem, and yet with the hose coiled you shouldn't get any water into the cabinet space.

I may not be the most highly trained mechanic, but I've gotten myself into and out of enough jams that McGuyver's got nothin' on me!

One last question, and sorry for the long post. I'm not sure I understand what you mean when you say that there's a "hole right through" the anti-siphon valve. If that's true, then you should be getting air into your system, which should break the siphon. That anti-siphon valve closes only when water pumps through when the bilge pump kicks on. The only thing I can think of is that there is a hole in your anti-siphon valve, which then leads to the vent hose, which itself runs down to a point lower than the through hull, which is what is causing your siphon. The more I blather on the more I think you really need to pull that vent hose out of the bilge, and that is the source of the problem, even if it manifested itself only recently with the broken vented loop.

Keep us updated as to how you're making out.


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## xort (Aug 4, 2006)

as a temp fix could you extend that hose that comes out of the syphon loop so it dumps overboard instead of the bilge?


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## eherlihy (Jan 2, 2007)

Labatt,

It's good to know that you and the family are still dry...

Last night, I was lying in bed thinking about this problem, and what may have started it. Even though the siphon vent tube is below the waterline, water should not have filled the vent tube, and the siphon should not have started. _Unless_ something is restricting the flow of water between the siphon break and the through hull.

My guess is that there is a restriction between the through hulll, and the siphon break. When the bilge pump kicks on, there is enough back pressure between the vent hose and the through hull to enable water to (follow the path of least resistance) fill the vent hose, and start a siphon. Marine growth, or a kink in the hose could be possible culprits. If the pump end of the hose is in a little bit of water, or if the check valve is closed it would provide the seal necessary to get the siphon going.

A possible temporary fix would be to pull the 1/4" siphon break hose up from the bilge, and run it out a port, as xort points out above.

You really should fix the bilge through-hull by repositioning it above the static water line. I would also get rid of the check valve. It is redundant if you have a siphon break.

HTH!!!

Stay dry!

- Ed


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## AdamLein (Nov 6, 2007)

eherlily: it doesn't need to be a solid restriction. IIRC, labatt's through-hull is below the waterline, so you have to include hydrostatic pressure when determining whether it is "higher" than the venting hose end.

Anyway wasn't it the conclusion that water is being siphoned in through that very through-hull? If so, it obviously isn't blocked....


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## eherlihy (Jan 2, 2007)

AdamLein,

I did not say, nor mean to imply, that the through hull was blocked. I agree that *any* restriction between the through hull and the siphon break would be sufficient for hydrostatic pressure to build in the siphon break, filling the vent hose with bilge water, when the bilge pump kicks on. Because the bilge through hull is below the waterline, when the pump shuts off, a siphon would start draining the ocean into his bilge through either the 1/4" vent hose, or the 1" bilge pump hose if the check valve is not functioning.

I find it suprising that a Perry designed boat would have this through hull below the waterline, and without a seacock. I am wondering if this is the way she rolled off the production line, or a PO modification.


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