So today I noticed and I notices it last year every time I flush my toilet on my boat the vent for my holding tank smells so bad. I don't know why but there isn't a vent filter and I can't believe it was like this when new. Is there some chemical I can add that will help or another vent? The holding tank should be getting Fresh air correct? It's on my 2001 DONZI 38zx

no, the holding tank has 1 vent to atmosphere. you add doo doo or peepee it pushes (smelly) air out the vent. that blue chemical helps but it is mainly perfume...

There is a charcoal filter on the vent, sounds like yours needs changed.

http://www.wholesalemarine.com/p/SEA...FWaFQAodaHjcFw

i dont have a charcoal filter on mine....its a mother F'er to get to the vent hose on the boat to even think about adding one

Empty your tank, refill it with fresh water and empty it again (instatly). I then added about half a tank of fresh water and Calgon water softner (liquid form) to the tank, drove around for a day and let slosh around. It cleaned and deoderized the tank. I usually add a couple gallons of fresh water after each pump out and bottle of the blue chemical, seems to be good now.

Holding tanks need a good supply of fresh air for the bacterial to break down the contents and not smell. With a lack of fresh air, a different type of bacterial is present that makes the smell. Can''t recall the different bacteria names.
A charcole filter will prevent the smell from escaping, although it is a band-aide vs addressing the issue of poor venting. Though they work, and they can not get wet. You do have to be carefull with the filters as they greatly restrict the air flow when pumping out, to the point that your tank will implode some. You are pumping out contents thru a 1 1/2 hose, while venting thru a 5/8" hose. Do the math.

WM carries a chemicle ( ODORS) thats way better than the blue stuff from Walmart.
Either way, you need a chemicle to help with the content breakdown.

I have a trailer and have had two trailers now old one was better than the other. Im assuming that boats are the same way. The only way I found to help this to flush the tank and flush again every couple of weeks. and always keep a little water in the tank with bleach while your not using it.

thanks for the input, i never added freash water and will flush it when i go back out there...also where can i get the Calgon water softner (liquid form) locally?

We picked it up at Walmarts.

You'll also find that if you add water to the bowl after using the toliet and rinse out the lines you're smell will decrease. It may require you to pump a little more but you may not smell as bad. We have a season pass so not as big of a deal for us.

You never want to keep a dry except winter well even then some pink stuff should be in there. When you leave it dry crap toilet paper and everything cakes. On the new trailer I got that was the problem the guy had the holding tank constantly open and which left the tank dry. take a dump and it cakes because it needs to be wet. Also be sure you are using the trailer TP which is also sold at Wallys, dont use regular toilet paper.