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Holding tank thruhull vent

5K views 20 replies 12 participants last post by  badsanta 
#1 ·
I am replacing all of my sanitation hose. The 5/8 hose that vents the holding tank connects to a 5/8" thruhull vent. The vent is corroded so I have removed it and plan to replace it. The outside part of the vent was 90 degees and streamlined facing aft. The open end had a screen in it. I can't seem to find anything that is similar to this. Would a different type of vent work just as well?
Thank you
 
#2 ·
You probably want something like this... :)

 
#3 · (Edited)
As long as your replacing it

... you'll benefit to going to 1"...it will alow for more air transfer which will greatly reduce oders..

Could also use a Fuel tank hull vent, as they have the screen on them also..

Woops nevermind SD has it already.. Dawg-gon robo typer...:)
 
#4 ·
LOL... :) :p
 
#5 ·
I just put in a holding tank in my boat.
For the vent I just put in a white plastic .75 inch diameter through hull. No screen.

I put it on the side of the hull.
Sounds unusual, but here is my thinking..

I wanted the extra diameter (1 inch dia is probably even better) to fight smells in the holding tank.

I routed the hose uphill inside the hull before it went downhill to the holding tank. This is to keep rain from filling up the holding tank.

I put the hole in the holding tank as far inboard as I could, so that if I burried the rail in the water, it still wouldn't fill the tank.

So, you're good. With the hole on the side, it is out of the way, and large.

gh
 
#6 ·
GH-

You'll probably regret not having a screen on the vent. Wasps and other critters will more than happily take up residence in the nice dark space you've provided. clearing them out will not be fun.
 
#8 ·
The down side of the screens is that if the tank fills up. Any... well we'll call it debri will clog up the screen and eventually keep the tank from venting properly With a straight through hull if it does become clogged you can use a water hose to clear the obstruction. you also eliminate a 90* turn at the fitting. They put screens in fuel vents as (flame arrestors?) Don't know the proper term but I bet BF does.
Put a rag in it when you store the boat.
Works for me. may not work for every one especially if there is no room to get the hose higher than the vent.
 
#12 ·
Though-hull vent fitting

Actually, the vent you had was a gas vent being used for a holding tank vent. They are hard to find. Here's a link to the only American supplier I could find. I haven't posted often enough to be able to give you the URL but the following info should get you there.

go2marine.com

It's a Perko - Gas Tank Vent

Good luck!
 
#13 ·
Lose the screen, spray vinegar into the vent

According to the "Head Mistress," urine + saltwater = calcium. I had exactly the same vent cover with screen and the screen was completely solid with calcium deposits.

I removed the vent cover and screen and now spray vinegar as far into the vent hose (from outside) as I can a couple times a month.

The Head Mistress' book on eliminating boat smells is well worth the $. This piece of advice alone has MUCH improved the holdling tank smell situation. It would be nice to have a much larger vent, but keeping this one clear helped enormously.

Mary
 
#14 ·
Mary-

If you're getting calcium in the vent hose and vent, you're probably over filling the tank on a regular basis.

According to the "Head Mistress," urine + saltwater = calcium. I had exactly the same vent cover with screen and the screen was completely solid with calcium deposits.

I removed the vent cover and screen and now spray vinegar as far into the vent hose (from outside) as I can a couple times a month.

The Head Mistress' book on eliminating boat smells is well worth the $. This piece of advice alone has MUCH improved the holdling tank smell situation. It would be nice to have a much larger vent, but keeping this one clear helped enormously.

Mary
 
#15 ·
One of the advantages . . . . .

. . . . of a black-water bag rather than a tank.

There is no need for a vent. The bag simply expands and collapses as required by the contents or lack therof.

Andre
 
#16 ·
. . . . of a black-water bag rather than a tank.

There is no need for a vent. The bag simply expands and collapses as required by the contents or lack therof.

Andre
Ultimately you would still have the same situation... for instance:

Take a garbage bag and fill it with liquids....

empty it out - smell still remain, repeat it gets worse and worse - yes because you can't get it all out...the bag for onboard still has to have a vent... if it doesn't when overfilled where does it go... over the flooring and into the bilge which further exasperates the odor...

Those bags are good for filling when it is a consumable item but not for waste...

IMHO
 
#19 ·
Andre-

The real problem with a flexible bladder tank for waste is that you'll only get the anaerobic bacteria in it... since there is no venting... and that means you'll get more odor from it...since the anaerobic bacteria are the ones that make the nasty sulfurous stench. Also, not having a vent means that if you over fill it, the hoses or bladder itself are more likely to burst, rather than spewing it out the vent line... which will have the effect of spewing it inside the boat. If I have a choice between **** running down the hull into the water and **** spraying the inside of my boat, I know which I'd pick.
 
#20 ·
Do you guys ever flush your holding tanks with treatments?

We do it regularly and when I disconnected everything from my "bags" there was no more smell from them than with a solid tank. As said, we pump water into the bag, squish it around and pump it out. Artbyjody, describe the cleaning process you use with your solid tank please. And without vents, who gives a toss what it smells like inside anyway??

And as also said, the head pump is physically incapable of putting enough pressure into the bag to burst it so how do you figure that it's a serious risk? You can't "overfill" it.

Andre
 
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