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Old 11-07-2019, 03:02 PM   #1
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Installing new through hull for holding tank breather

I am going to add a second breather to the holding tank to try and get some more air/oxygen into it to reduce the killer smell coming out the single vent when we flush.

It will be in the side of the hull, well above the water line, roughly half way between the water line and the gunnel. The hull is solid glass.

Question: Once I have drilled the hole with a hole cutter, is there anything I need to do to the hole before installing the fitting and sealing it with Sika?

BTW, the second breather will be fairly close to the existing one. I intend fitting a small scoop over one of them (facing away from the bow) the idea being to set up a small amount of suction which will hopefully draw air into the tank via the other breather, or act as a scoop if the wind is blowing the other way.
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Old 11-07-2019, 03:14 PM   #2
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Since it is solid glass then sealing with Sikaflex is all you need to do. Does your second vent connect to the holding tank separate from the existing one? That is the best way to suck out the vent space.

But I would first increase the diameter of the existing vent hose. That is what Peggie- the Head Mistress, always recommends.

Also make sure that both vent hoses are routed uphill from the tank with no low spots.

David
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Old 11-07-2019, 03:48 PM   #3
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You should round the outside edge of the hole in the hull so that the Sika will make an O ring around the through hull fitting.
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Old 11-08-2019, 06:28 AM   #4
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All sealants have a limited life.

I would use a bit of Epoxy to seal the cut , then use your favorite goop.
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Old 11-08-2019, 08:17 AM   #5
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Two vents on the same side, close to each other ? Doesn't make good sense. You really want the new vent on the opposite side of the boat so as to add cross ventilation. A breeze or the motion of the boat with both vents on the same side will merely "air block" the tank. Not serious but will not cause good ventilation.

Please rethink the new vent.

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Old 11-08-2019, 09:35 AM   #6
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Increasing the ventilation in the tank is the key to preventing odor, but I'm not crazy about the way you plan to do it. However, I need more information about the location of the tank and other details before I can recommend the best way to do it. So if you'd like to send me a PM that includes your email address (so we can move the conversation to email which is sooo much easier than PMs!) I'll be glad to help you sort out what to do to get the results you want.


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Old 11-08-2019, 03:18 PM   #7
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Quote:
Originally Posted by Pete Meisinger View Post
Two vents on the same side, close to each other ? Doesn't make good sense. You really want the new vent on the opposite side of the boat so as to add cross ventilation. A breeze or the motion of the boat with both vents on the same side will merely "air block" the tank. Not serious but will not cause good ventilation.

Please rethink the new vent.

pete
Pete,

Your advice is good, but unfortunately the tank is located on one side of the ER and it is not feasible to run a line to the other side - it would have so many dips, twists and turns that it certainly wouldn`t be a straight uphill run to the outlet as the new one will, alongside the existing one - that's why I was putting the clam shell over one of them - to get a venturi effect - hopefully air being drawn out by that one.

Appreciate your concern though.
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Old 11-08-2019, 05:25 PM   #8
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Could the second vent be on the same side but at opposite ends of the tank... fore & aft??? Instead of near or adjacent?
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Old 11-08-2019, 05:42 PM   #9
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George, there was a "pong" around the tank in the ER 10 years ago, then I think it was a Lectrasan system. Hope it goes well.
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Old 11-08-2019, 06:51 PM   #10
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Try and move the new vent so its forward of the parallel sides of the hull, then you will have forced air moving through the tank at anchor and underway. I used 1 1/2” sched 40 pvc pipe for all my poop plumbing. Both vents and piping.
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Old 11-09-2019, 07:10 AM   #11
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More ventilation should work , but a small air pump might be less effort and is sure to work.
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Old 11-12-2019, 10:12 AM   #12
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Try this first... put a filter on the air vent hose. They sell charcoal filters for this application. I did a DIY solution, by inserting a length of 1.5" PVC pipe filled with fish tank charcoal pellets. I did not glue the top cap so I can replace the charcoal every year or so. Since I have a fresh water electric head, the vented odor is not that bad, but a filter will minimize the odor.
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Old 11-12-2019, 12:22 PM   #13
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Quote:
Originally Posted by Puffin_NT32 View Post
Try this first... put a filter on the air vent hose. They sell charcoal filters for this application. I did a DIY solution, by inserting a length of 1.5" PVC pipe filled with fish tank charcoal pellets. I did not glue the top cap so I can replace the charcoal every year or so. Since I have a fresh water electric head, the vented odor is not that bad, but a filter will minimize the odor.
Better to get adequate air in and have no odor to filter out
Filters ensure the tank will smell.
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Old 11-12-2019, 12:23 PM   #14
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Better to get adequate air in and have no odor to filter out
Filters ensure the tank will smell.
+1. No vent filters but add more air and the tank wonít smell.
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Old 11-12-2019, 12:43 PM   #15
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Quote:
Originally Posted by HeadMistress View Post
Increasing the ventilation in the tank is the key to preventing odor, but I'm not crazy about the way you plan to do it. However, I need more information about the location of the tank and other details before I can recommend the best way to do it. So if you'd like to send me a PM that includes your email address (so we can move the conversation to email which is sooo much easier than PMs!) I'll be glad to help you sort out what to do to get the results you want.


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This lady here, Peggie, knows her stuff on marine waste systems. She has a book specifically on dealing with waste systems and their problems. It's sold on amazon in any format you could want and very reasonably priced. Everyone that owns a boat with a head or toilet should have at least one copy. I recommend two, one for the boat and one to keep close at hand when dealing with head problems off the boat.


https://www.amazon.com/gp/product/18...language=en_US
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