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-   -   Holding Tank Vent Filters (http://www.sailnet.com/forums/gear-maintenance/47270-holding-tank-vent-filters.html)

jbondy 09-19-2008 01:52 PM

Holding Tank Vent Filters
 
In the last three years, I've replaced the holding tank, head, macerator pump and all hoses. Of late, the only real aroma I've had to deal with is when the head is flushed. The smell that comes through the vent wafts aft and is strongest in the cockpit, embarassing to the head user, to say the least. Sealand (and others) market vent filters that they claim will eliminate this particular aroma. Has anyone any experience with these?

TIA

petegingras 09-19-2008 02:19 PM

I can attest to the vent filters effectiveness. Although the charcoal will have to be replenished annually, (the charcoal is readily available at the pet store same as you’d use to filter water in a fish tank) or you can replace the entire filter if you’re willing to shell out the $80 or so dollars annually.

sailingdog 09-19-2008 02:27 PM

IMHO, it isn't worth spending the money on the vent filter line, since it really is going to only make the problem worse. The problem is that you probably don't have sufficient ventilation for your holding tank, and adding a filter is going to make that worse, not better. The odor-causing bacteria are anaerobic, and if you increase the ventilation to the tank, it won't stink, since the good aerobic non-sulfide producing bacteria will multiply and the sulfide producing anaerobic bacteria will die off.

Another problem with stinking holding tanks is when you flush using seawater, since the seawater often contains small lifeforms that will die and decompose, adding to the smell...but that usually is more a problem in the hoses than the holding tank itself.

jbondy 09-19-2008 03:16 PM

Thanks. I flush with fresh water, so that's not the issue. I've thought about increasing the vent hose size (currently 1/2" i.d.) and running two of them. One issue is how to attach the hose to the tank. There's no access port and I'm reluctant to add one -the fewer holes the better! So I can't put one of these in.

http://www.defender.com/images/500497.jpg

The tank is plastic, so I wouldn't think I could tap threads for one of these:

http://www.defender.com/images/500478.jpg

And it doesn't make sense to me to attach a 1" i.d. hose to a 1/2" opening.

Also, the screened vent to the outside would need to be replaced with something I have yet to find.

Any ideas would be appreciated. TIA

sailingdog 09-19-2008 03:20 PM

Before doing any of that, it might be worth checking the existing vent line to see if it is clogged. Wasps and other bugs love to build in the vent lines. Also, if you've ever over filled the holding tank, it could have less desireable materials clogging it.

sailboy21 09-19-2008 03:58 PM

Quote:

Originally Posted by sailingdog (Post 371432)
Before doing any of that, it might be worth checking the existing vent line to see if it is clogged. Wasps and other bugs love to build in the vent lines. Also, if you've ever over filled the holding tank, it could have less desireable materials clogging it.

I have had this problem a lot. My tank is small, and the vent is right over the tapered end of the tank. Even if I didn't overfill that tank a spirited sail seems to be enough to clog the tube. I have made it a routine to reverse flush the vent line every time I pump out. This seems to be working so far... Use some old battery cable or similar stiff wire to clear any obstructions. Yummy...

jbondy 09-19-2008 04:53 PM

How do you reverse flush the vent line? Do you just push a hose over the vent? On Pokey, the vent itself is a screened doohickey that protrudes from the hull below the rub strake. We usually avail ourselves of a pumpout boat or pump overboard and are hardly ever at a dock. (We keep her on a mooring.) Just wondering. Thanks.

sailboy21 09-19-2008 06:10 PM

Quote:

Originally Posted by jbondy (Post 371520)
How do you reverse flush the vent line? Do you just push a hose over the vent?

That is exactly what I do. I stick a chunk of vinyl tube over the end of the garden hose and stick it over the vent while pumping out. Seems to do the trick, but just make sure everything is hose clamped! That said, if you really got a good hookup there is a risk of pressuring the holding tank and other associated fittings not normally under pressure so be careful.

JimsCAL 09-19-2008 06:57 PM

I doubt the vent alone is going to be enough to get fresh air into the tank unless the hose run is REALLY short. There are systems on the market that supply a small flow of fresh air to the tank. That seems to me the only way to insure growth of aerobic bacteria.

travler37 09-19-2008 07:49 PM

Add This
 
The basic problem is not enough aerobic bacteria.
Try Home depot or another such store for HOME septic tank treatment.Add this to your holding tank and vent line.Worked for me.
Mark


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