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Old 15-02-2011, 08:19   #16
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I think you can really simplify things.

First, if you are living on the boat, it is not necessary to have a vented loop on normal toilets, because the joker valve will normally prevent backflow. If the joker valve fails, waste water will start to SEEP back into the toilet. Its then time to either treat the toilet with vinegar to dissolve the uric salt deposits or replace the joker valve--something that happens on the order of once per year. If you don't catch the seepage in time its messy, but the automatic bilge pump system on any boat can easily handle the leakage. If you are off the boat for more than 24 hours, simply close the through-hull.

Secondly, the vacuflush toilets normally have a diaphragm pump to flush them, and this diaphragm pump has one-way valves on both the inlet and outlet side of the diaphragm. In order for a vacuflush toilet to leak back into the bowl, BOTH valves have to fail. The need for a vented loop there is even less for the reasons stated above.

Thirdly, the pumpout of the holding tank really doesn't need a vented loop at all. As you have figured, that thru-hull valve is only opened when you are pumping out.

Finally, your unvented loops are just a waste of hose.

Not sure how you empty your holding tank overboard, but if it's with a diaphragm pump, you can eliminate one of the thru-hulls and T into the other.
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Old 15-02-2011, 08:23   #17
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you don't need a vented loop if going directly into the holding tank .. if the toilet is lower than the tank you may have an issue. an overboard pumpout can be done without a loop if you keep the thru hull closed when not doing a pumpout. also put the thru hull at waterline. on the self draining tank: they have been known to clog and i would not want to solve that problem.
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Old 15-02-2011, 17:52   #18
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What does everyone have against vented loops and a little extra hose? If the smell is your concern, the loop can be vented overboard. I sleep a lot better at night knowing that my boat will not sink if my kids forget to close the thru hull.
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Old 15-02-2011, 18:02   #19
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according to your drawing sketch there are still little dips in the vent line, you want to get those out of there so they dont hold moisture/water. Also when using the pump out from dockside i hope you have a anti- implosion valve on the tank otherwise the pumpout will create a vacume and 'splode your holding tank expecially if if you dont have one and your vent line is plugged.
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Old 16-02-2011, 03:50   #20
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according to your drawing sketch there are still little dips in the vent line, you want to get those out of there so they dont hold moisture/water. Also when using the pump out from dockside i hope you have a anti- implosion valve on the tank otherwise the pumpout will create a vacume and 'splode your holding tank expecially if if you dont have one and your vent line is plugged.
Good points. The vent line will be re-routed.
It has a vacuum relief valve.
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Old 16-02-2011, 03:59   #21
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Originally Posted by gonesail View Post
you don't need a vented loop if going directly into the holding tank .. if the toilet is lower than the tank you may have an issue. an overboard pumpout can be done without a loop if you keep the thru hull closed when not doing a pumpout. also put the thru hull at waterline. on the self draining tank: they have been known to clog and i would not want to solve that problem.
I will do this next haul-out refit.
Good idea to have the one thruhull at the waterline...
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Old 16-02-2011, 04:01   #22
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Originally Posted by donradcliffe View Post
I think you can really simplify things.

First, if you are living on the boat, it is not necessary to have a vented loop on normal toilets, because the joker valve will normally prevent backflow. If the joker valve fails, waste water will start to SEEP back into the toilet. Its then time to either treat the toilet with vinegar to dissolve the uric salt deposits or replace the joker valve--something that happens on the order of once per year. If you don't catch the seepage in time its messy, but the automatic bilge pump system on any boat can easily handle the leakage. If you are off the boat for more than 24 hours, simply close the through-hull.

Secondly, the vacuflush toilets normally have a diaphragm pump to flush them, and this diaphragm pump has one-way valves on both the inlet and outlet side of the diaphragm. In order for a vacuflush toilet to leak back into the bowl, BOTH valves have to fail. The need for a vented loop there is even less for the reasons stated above.

Thirdly, the pumpout of the holding tank really doesn't need a vented loop at all. As you have figured, that thru-hull valve is only opened when you are pumping out.

Finally, your unvented loops are just a waste of hose.

Not sure how you empty your holding tank overboard, but if it's with a diaphragm pump, you can eliminate one of the thru-hulls and T into the other.
thanks
it has a diaphragm pump - and will eliminate both thru hulls and install one at the waterline next haul-out...
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Old 16-02-2011, 04:11   #23
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Yes the loops without vents are pointless as anti-siphon devices.

If the run of hose never goes above the waterline, then as soon as you open the seacock water will come in and fill the tank below the waterline. So the loops above the waterline even without vents are needed for that purpose.

The head being above the waterline is not a consideration, but your vacuflush tank and holding tank are below the waterline. They have ports, vents, fittings, whatever, if any of that leaks when you create a siphon those leaks will fill the boat. At least in the U.S. a survey for insurance or selling will probably point this out as a problem. They won't care if your usage pattern is safe by always closing the seacocks, the system must be installed as idiot proof as possible.

How old are the hoses? You have to replace them every 3-5 years as they permeate and the smell comes through the hose. With those length of runs I could start the great PVC debate again.

So if I understand your system correctly, with the vacuflush directed to overboard, there is something on the order of 40' of hose sitting in your boat with sewage sitting in it. How many flushes would it take to transport that out of the hose? Sounds like a very less than ideal situation from both the sedimentation and smell problems.

John
thanks.
there would be 80'.
There is 10' out and 10' back of (allegedly)redundant hose from both the toilet pump, and the holding tank pump. Same system port and Starboard.
plus the 5/8" ineffectively routed vent line on each system. All under the bunks.
Was thinking about the survey issue. And, well I will deal with that in 10 years. Can always put them back(and better).
I reckon the hoses are quite old - didn't realize they deteriorated - guess I can't sell them now...Maybe buy new sections of "better" hose, rather than cutting and reconnecting.
Another issue with my system and accidental discharge from the holding tank. The on/off switch is on the circuit board alongside everything else. Push the wrong button and it is instant-on and overboard.
I don't think this is good (or acceptable to LEO). Maintaining the (difficult to get to) sea-cock in the closed position would be prudent.
thanks.
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Old 18-02-2011, 09:22   #24
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Hooboy...where to begin???

There have been so many replies that I'm not even gonna try to sort through all of 'em...I'm just gonna start from scratch to answer the question.

Quote:
Originally Posted by AllezCat View Post
Hi All,
So I have a vacuflush head and Sealand holding tank system in the bilge.
There are 2 independent thru hulls:
One line is form the head to thruhull #1;
The other line is from the holding tank to thruhull #2.
But, both 1 1/2" head hoses run from the bilge amidships aft, then up above the waterline directly below my pillow.
It really stinks. probably from the previous owner(can't be from me).
So I intend to reroute the lines forward under the bathroom vanity(same height).
This is going to be a shitty job.
Just wandering if the above waterline loops are even necessary?
or mandatory?
Also while checking this I found the vent line runs downhill before exiting somewhere(still looking)...This could be a problem too, yes/no???
thanks for your help...
No vented loop is in needed in any head discharge line that goes only to the tank. However, one IS needed in any line connected to a below-waterline thru-hull. So you'd need one in the line from head #1 and one in the line from the tank to thru-hull #2...that one goes AFTER the pump, between the pump and the thru-hull.

Vented loops should have an air valve in the nipple that only allows air INTO a line to break a siphon...nothing out. Air valves are replaceable parts that have a lifespan and also need periodic cleaning. So if your vented loops are squirting or outgassing, tend to the air valve instead of going through the agony to reroute hoses. That is, UNLESS you can shorten the runs considerably by rerouting the hoses and moving the vacuum pump(s). Then it's worth doing.

And it may be helpful to understand just how a VacuFlush works. The accumulated suction only moves the bowl contents as far as the vacuum pump...then the vacuum pump does two things simultaneously--it pulls the air out of the system between the bowl and the pump while it pushes the flush the rest of the way to the tank or thru-hull. How long the pump runs depends on the distance from the bowl to the pump...the shorter that is, the shorter the pump run time. If that's not long enough to push the flush all the way to the tank or thru-hull, it's gonna sit in the line till it gets another push from the next flush.

Hopefully that will help you decide whether you need to move any plumbing--whether you SHOULD or not...and where to put it if you do.

It's also possible that your odor is caused by permeated hoses...if so, the only cure: new hoses. The best on the market today is Trident 101/102 Trident Marine: Sanitation Hose (identical except for color). It's a double walled rubber hose that's been on the market for more than 15 years without a single reported odor permeation failure...something that cannot be said about ANY other hose including SeaLand OdorSafe...I've personally been on half a dozen boats on which OdorSafe has failed and heard of dozens more.

About the tank vent line...a slight downhill run to vent thru-hull isn't the best idea, but isn't a problem unless the vent line is longer than a couple of feet and the "hill" is more than just slight.

This isn't the most fun job, but it doesn't have to be THAT bad if you'll take the time to pump out the tank and then thoroughly rinse out the whole system by running GALLONS of clean water through it. Catch any spills by putting disposable foil pans or trash bags under fittings.

I think that about covers it...
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Old 18-02-2011, 12:02   #25
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Lightbulb Alternative 3-Step Program

Step 1 - Remove the whole mess
Step 2 - Remove the thru-hulls and glass over the holes at next haulout
Step 3 - Install composting toilets

Pros:
No danger of flooding
No periodic replacement of expensive hoses
No thru-hulls to maintain
No pumps to maintain
No fresh water wasted on flushing
Reclaimed storage space where the hoses used to be
No pumpouts
No stink.

Cons:
Minor learning curve on use of composting vs. traditional heads

No affiliation with any composting toilet makers, but I am in the middle of this project on Adagio.
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Old 20-02-2011, 16:04   #26
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Vacuum relief valve is not a substitute for tank vent maintenance

Quote:
Originally Posted by AllezCat View Post
Good points. The vent line will be re-routed.
It has a vacuum relief valve.
I don't like 'em, 'cuz they they have an air valve not unlike the air valve on a vented loop that only opens to allow air INTO the tank to prevent it from imploding during pump if the vent is blocked. They don't prevent the tank from becoming pressurized when the air in the tank displaced by incoming waste can no longer escape out the blocked vent. And a pressurized tank can EXplode. It doesn't occur to people that a blocked tank vent is what's causing increasing back pressure or increasingly sluggish discharge...they think they have a clog, so they pressurize the system even more by trying to flush out the clog. However, exploded tanks are rare...a pressurized tank usually just erupts in the owner's face when he removes the cap on the pumpout fitting...causing great explosions of mirth from onlookers at the pumpout dock.

So yes...do straighten out and shorten up the vent line...and maintain the tank vent. Never let the tank overflow out the vent. Check the vent thru-hull regularly...'cuz dirt daubers love to build nests in 'em. Best if you can backflush it every time you pump out and/or wash the boat.
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