Obsolete knowledge

[Peggie Hall HeadMistress]

To email any registered poster including me

Just click on my name in the box to the left....you'll see options to view public profile, send a PM or send 'em an email. Click on the one you want to use. I much prefer email over PM, btw.

 

[Guest]

Tank

Hi Bill, perhaps Peggie is right, but without actually having a copy of the ABYC standards that stipulate the requirement, I suspect your boat model like ours does not have a vented loop designed into the referenced system for a reason. To say it was for cost reasons is being a bit disingenuous. Hunter Marine Customer Service can provide an explanation as to why they designed the system without one.

If it were my boat I would contact Ronco product support requesting a specific explanation as to what purpose the vented loop serves. Then Hunter Marine Customer Service for theirs. I still fail to see the risk.

A vented loop for the engine cooling system makes sense because of the risk of back wash damage. Like wise for the siphon break in the toilet vented loop raw water intake. It is not there for the reasons of a hose slipping off or a fitting break. There are other measures for that.

My insurance company nor marine surveyor gave me no indication that they expect me to redesign my boat to meet some new or revised standard. If a vented loop were required as a safety measure in the event of a hose slipping off or a fitting break, our boat would have one on all through hulls. Such is not the case, FWIW.

Terry Cox

 

[Head Master18695]

Re: Tank

Terry, I've been in the marine sanitation business for 38 years now. I'm with Raritan Engineering Company, one of the major manufacturers of marine toilets and sanitation equipment, to include the PHII marine toilet, Crown Head, Atlantes head, SeaEra head, Marine Elegance head, discontinued Lectra/San and current Electro-Scan treatment systems, Purasan and ManaGerm treatment systems - perhaps you've heard of some of them. My title is Senior Technical Advisor. My phone is the first to ring whenever someone calls in, looking for Technical Support on a Raritan product. I even get occasional calls from Coast Guard compliance officers, for clarifications on the sanitation laws because they don't always understand exactly what they're supposed to be enforcing.

According to ABYC, any piece of sanitation equipment, to include holding tanks and macerator pumps that lead to a through-hull that is below the waterline of the boat, MUST have a vented loop as the last component before the through-hull fitting. The top of the vented loop is supposed to be a minimum of 4" above the waterline, at the greatest anticipated angle of heel.

Simply because the builder didn't supply one with the boat, doesn't mean that it isn't a requirement. And even if it weren't a requirement, it would still make good sense to provide one, for safety's sake. I agree that a boat can sink for any number of reasons, but why add one more possibility? This is no new or revised standard - I know for a fact that it has been an ABYC standard since the 1960's, and probably long before that. And again, should a boat sink, the insurance company will not be looking for reasons why they SHOULD pay the claim; they'll be looking for reasons why they SHOULDN'T pay the claim.

Remember, the Ark was built by amateurs and the Titanic was built by professionals? Which one fared better?

I'd said my piece, and won't have any more to say on the issue.

 

[Guest]

Tank

Thanks for the input. Has this requirement always been a part of the Standard or is it a recent edition? It seems odd that a boat builder would intentionally violate an industry standard, such as in our case, just to save a buck. In Bill's case he was considering relocating the tank beneath the forward berth, which in our case (likely in his, too) would place the tank above the waterline. Regardless, at some point when I replace our SS tank, I will leave the original system configuration as designed by Hunter. I still fail to see any substantial risk in the absence of a loop; perhaps I'm blind. The risk would be no more or less than any other through hull on our boat, absent my previous points regarding toilets and engines.

Again, thanks for your comments and Happy New Year.

Terry Cox

 

[Guest]

Boats

In reference to the Ark versus Titanic, the reason why the Ark fared better was not because it was built by an amateur, but because it was designed by and built with the assistance of the Master boat builder. Unlike the Ark, the Titanic contained several man made flaws, which contributed to its demise.

Terry Cox

 

[Ron20324]

Bill, inasmuch as ABYC and toilet maufacture's may call for a vented loop, if there is not one placed, I suspect the boat manufacturer figures the prudent skipper will close the thruhull when the macerator(or any device) is not in use- much the same as you would/should close ANY thru-hull when leaving the boat when not in use. I'm on my second Beneteau and neither one of them had a loop betweeen the pump and the bowl- contrary to Jabsco's owner manual.

 

[Peggie Hall HeadMistress]

You suspect wrong...

I suspect the boat manufacturer figures the prudent skipper will close the thruhull when the macerator(or any device) is not in use-

The real reason is...vented loops cost money, for the loop and the additional amount of hose needed, and the added labor to install it. Boat builders omit them to save the cost. Some even put toilet/tank overboard discharge thru-hulls above the waterline to save the cost of the seacock...most will use a tee or a wye instead of a y-valve to save money.

Unlike building codes on land and those required by the CFR, compliance with ABYC standards is voluntary. You'd be amazed at the number of 'em that 99% of builders ignore to save a buck.

The prudent skipper will make the necessary corrections to protect his boat.

 

[catsailor]

If the pump-out pump in a diaphram type (2 checks valves are integral) does the AYBC still require..

The real reason is...vented loops cost money, for the loop and the additional amount of hose needed, and the added labor to install it. Boat builders omit them to save the cost. Some even put toilet/tank overboard discharge thru-hulls above the waterline to save the cost of the seacock...most will use a tee or a wye instead of a y-valve to save money.

Unlike building codes on land and those required by the CFR, compliance with ABYC standards is voluntary. You'd be amazed at the number of 'em that 99% of builders ignore to save a buck.

The prudent skipper will make the necessary corrections to protect his boat.

....a vented loop? Does the code speak to check valves? I'm curious.

Are check valves perfect? No, they can easily hang open a bit. Can a vented loop plug? Yes, I have seen that happen.

That is the installation in my boat (head to the to the top of the tank, with a y-valve to either pump-out or a diaphragm pump overboard, with no loop vent). Only about 15% of the holding tank is below the waterline and the holding tank is in a bulkheaded compartment. The bowl lip is ~ 4" above the waterline.

 

[Chuckbear]

....a vented loop? Does the code speak to check valves? I'm curious.

ABYC as Peggy said are standards. They are not code and they are not laws. They are guidelines only. Chuck

 

[catsailor]

Yes, I understand that. My bad.

ABYC as Peggy said are standards. They are not code and they are not laws. They are guidelines only. Chuck

There are many industry standards with similar standing - good conservative advise, but not law.

I am still curious regarding check valves. I use many diaphram pumps in industrial and refinery settings, and because there are double check valves, they are quite resistant to back flow. Normally they fail to pump first. That said, I wouldn't trust one if the tank were further below the water line.

Also, the pump is mounted high, so that a diaphragm failure will not cause flooding. This is a significant risk, since failures are not uncommon and are often catastrophic. Mounting one low without a vented loop back-up would be chancy, in my experience.

 

[txtowman]

All hail the head-mistress

I'll take her side. y'all are bein' silly!

 

[Ron20324]

Bill, back to your original post... Don't know what the odds are, but Y valves are a possible point of failure. The handle breaking off seems to be a prime problem. Simplicity of any system lessens the chance of failure.... A TEE fitting will do pretty much the same as a Y as long as the deck cap is in place.... The pump below the tank most likely means it is gravity-fed- depending on the plumbing... The location of the tank usually dictates the location of the connections, and yes, them being accessible is a BIG plus..... A tank (of any use) location and boat layout/construction may not have room for the vented loop hose. Again, a line without a check valve will not flood- if you close the thruhull like you're supposed to.... Forget a check valve in the waste line. The first time it fails and you have to deal with it, you'll probably remove it anyway. Even high-quality check valves can fail- just like the ones in our our heart do.... You should always run a good flush of fresh water through the macerator after each use.

 

[SpencerW]

I want to thank Peggy for her service to me and our community. She has no agenda, except to help us all be safer and sweeter in ou beloved boats.

I just sold my 1989 Hunter Vision 32 and it did have a vented loop just before the thru hull. What may be at play here is that owners do modify their own boats. If you check again for a loop you may find it buried deep. It would be connected directly to the thru-hull. My loop was up and away and quite difficult to get to.

 

[Guest]

Vented loops

Lots of interest in the vented loop topic. Still a bit of a puzzle to me why the ABYC standard requires a vented loop between the macerator pump and sea cock. If it is a safety issue, as some have stated, then why no vented loop in the galley sink, cockpit drains, head sinks, etc.? To say that the vented loop is there to help prevent the boat from sinking in the event someone leaves the sea cock open and a hose slips off or a fitting breaks seems unorthodox to me.

It makes sense to have a vented loop for the engine exhaust, raw water intake for engine cooling, toilet raw water intake, etc., because there you have a potential risk of water back wash or siphoning continuing after flushing. In the case of the macerator that evacuates holding tank contents, with the tank above the waterline, where is the risk? If the sea cock is left open, water will slowly seep by the impeller and into the holding tank until water level is reached. In this case the original poster was placing the holding tank beneath the forward berth placing the tank above the water line. Virtually no chance of water back washing into the boat.

Then again lots of things make no sense to me, a novice on the topic. If the experts believe a vented loop is needed between the macerator pump and sea cock, then follow the expert advice. That way you will not succumb to, "I told you so". As was stated earlier, the ABYC standards are just that voluntary compliance.

Terry Cox

 

[catsailor]

Vented loops are for pressurized (generally discharge) lines and generally not intakes.

Lots of interest in the vented loop topic. Still a bit of a puzzle to me why the ABYC standard requires a vented loop between the macerator pump and sea cock. If it is a safety issue, as some have stated, then why no vented loop in the galley sink, cockpit drains, head sinks, etc.? To say that the vented loop is there to help prevent the boat from sinking in the event someone leaves the sea cock open and a hose slips off or a fitting breaks seems unorthodox to me.

It makes sense to have a vented loop for the engine exhaust, raw water intake for engine cooling, toilet raw water intake, etc., because there you have a potential risk of water back wash or siphoning continuing after flushing. In the case of the macerator that evacuates holding tank contents, with the tank above the waterline, where is the risk? If the sea cock is left open, water will slowly seep by the impeller and into the holding tank until water level is reached. In this case the original poster was placing the holding tank beneath the forward berth placing the tank above the water line. Virtually no chance of water back washing into the boat.

Then again lots of things make no sense to me, a novice on the topic. If the experts believe a vented loop is needed between the macerator pump and sea cock, then follow the expert advice. That way you will not succumb to, "I told you so". As was stated earlier, the ABYC standards are just that voluntary compliance.

Terry Cox

They are to prevent siphon where both ends are below or very near the waterline. Sometimes, in industry, they are called vacuum breaks. On an intake or suction line, they prevent suction. Not good.

 

[Guest]

Vented loops

whoooboy, now I'm really confused, more so than before.

Terry Cox

 

[woodster]

let me get this sorted out in my mind....

...being the novice that i am ...

the vented loop seems to prevent syphoning in either direction as i see it ..by letting air in the very top of the loop via a little ball valve that stays closed when there is fluid being pushed either way ...but when you try to suck from either end the little ball valve opens and stops the sucking action at the other end of the hose/pipe .....and by setting the loop above the water line...insures there will be no unwanted waste or sea water going in or out of the system via vacuum action ......

not sure how much theses little rascels cost but i like the fact that they controll the flow with out the aid of electrics and if you forget to close the sea cock you are still procteded.......this is better than haveing to ck the sea cock especially when you are 200 miles away from your boat and happen to wonder if you closed your sea cock or not ...i am in favor of the thing being on board and in good repair....

....now if i could only think of a way to make a siphone system for the bilge that would work with out a pump of any sorts......

 

[Peggie Hall HeadMistress]

Not quite true, Cat...

You said, "Vented loops are for pressurized (generally discharge) lines, and generally not intakes."

In fact, vented loops (siphon breaks) are essential in iintake lines, because a siphon is started by PULLING liquid through a line...which is what intake pumps do. A vented loop has an air valve in it (it's located at the top of the loop, and is usually a replaceable part) that opens to allow air into a line through which liquid is being pulled--which is what breaks the siphon--but shouldn't allow anything to escape. A siphon break has no effect whatever on liquid being PUSHED through a line.

That's why the vented loop in the toilet intake has to be installed between the pump and bowl instead of between the thru-hull and the pump. The pump PULLS water through the line to the pump, then PUSHES it to the bowl. So a vented loop in the line between the thru-hull and the pump would interfere with the pump's ability to prime...but doesn't interfere with its ability to push water to the bowl.

However, a siphon CAN be started by pushing water through a line when conditions are "right"...which is why vented loops are recommended in holding tank overboard discharge lines and toilet discharge lines and even sink drains. If you've ever see a fountain in the sink, the same thing can happen through any open thru-hull. If it starts in a holding tank, the tank can overflow back to the toilet, causing the toilet to overflow and can sink a boat. You can argue that you "always" close the seacocks...but I've never met anyone yet, including me, who's never forgotten to do it at least once....and vented loops are cheap backup fail-safe devices.

 

[catsailor]

Actually, we are saying the same thing, but your explaination is more detailed.

You said, "Vented loops are for pressurized (generally discharge) lines, and generally not intakes."

In fact, vented loops (siphon breaks) are essential in iintake lines, because a siphon is started by PULLING liquid through a line...which is what intake pumps do. A vented loop has an air valve in it (it's located at the top of the loop, and is usually a replaceable part) that opens to allow air into a line through which liquid is being pulled--which is what breaks the siphon--but shouldn't allow anything to escape. A siphon break has no effect whatever on liquid being PUSHED through a line.

That's why the vented loop in the toilet intake has to be installed between the pump and bowl instead of between the thru-hull and the pump. The pump PULLS water through the line to the pump, then PUSHES it to the bowl. So a vented loop in the line between the thru-hull and the pump would interfere with the pump's ability to prime...but doesn't interfere with its ability to push water to the bowl.

However, a siphon CAN be started by pushing water through a line when conditions are "right"...which is why vented loops are recommended in holding tank overboard discharge lines and toilet discharge lines and even sink drains. If you've ever see a fountain in the sink, the same thing can happen through any open thru-hull. If it starts in a holding tank, the tank can overflow back to the toilet, causing the toilet to overflow and can sink a boat. You can argue that you "always" close the seacocks...but I've never met anyone yet, including me, who's never forgotten to do it at least once....and vented loops are cheap backup fail-safe devices.

You made it clear to all readers, I hope, with the example of the head intake; the break goes in the pressure line (pump discharge, as I said) and not the actual suction line (which was my point).

Still, I am curious, does the AYBC standard speak to diaphragm-type pumps installed high on black water tank systems? I am not asking about risk, to be clear, only about what is stated in the book.

 

[Maine Sail]

A prime example of why a siphon break/anti-siphon/vacuum breaker/vented loop is a good item to have is one I came across about 12 years ago.

The boat, a 1980 C-30, had a macerator installed, can't recall whether it was a Jabsco or Johnson, but the pump head where the impeller mounts to the motor body began to corrode badly to the point where two of the four bolts holding the head onto the motor had snapped. The boat had no siphon break and thus the pump was leaking badly and cycling the bilge pump.

It took a while to figure out where this water was coming from as the pump was burried into the bilge, space was tight and visibility to the impeller end was non-existent. I finally figured it out with some brown grocery bags under the pump isolating the drip. When I replaced that macerator I installed a vented loop.

On most boats the macerator, if electric, will be placed low in the boat to suck from the bottom of the holding tank, usually below waterline or close to it. These pumps can and do fail and corrode. Without a vented loop you could potentially sink your vessel if the pump did as the one on the C-30 did.

Since this event I have replaced a fair number of macerator pumps. As soon as you see white corrosion between the pump motor and the plastic mascerator inlet/outlet head you should at the least tear it down and rebuild it or replace it altogether. Rebuilding these pumps is actually quite easy..

As for siphon breaks, the best vented loops or siphon breaks I have ever used are made by Scot Pump Company in Florida. They are a 316 stainless tube with a white plastic vacuum breaker.

I only know of one distributor of these excellent siphon breaks locally and that is:

Portland Yacht Services Parts Department
Joe Glantz
207-774-2408

Joe can also sell you a new breaker minus the u-shaped tube for about $20.00

Complete unit prices:
1/2" = $48.00
5/8" = $50.00
3/4" = $62.00
Call Joe for other sizes.

Vacuum breaker only price:

VB-18 (1/8") = $20.00

also comes in VB-38 (3/8") and VB-34 (3/4")

Note: the vacuum breaker is identical on all sizes and only the 1/8, 3/8 or 3/4 bottom threaded adapter fittings are different.

Complete unit:

VB only

I used one on my own boat as I have found no siphon break that works better or lasts longer (my piping is custom made and I just stuck the VB-34 on it):

[/quote]

For a waste system you will want to use the smooth radiused stainless tube to prevent clogging. For my raw water system on my motor I made my own siphon break with bronze fittings. That vacuum breaker has 3000 engine hours of use!!!!