I have done a 'cut & paste' to a previous post I made last June 15, 2017, below. A lot of folks use the filters, and some have had great results. However, if you do some research as outlined below, you will find that the odor can be eliminated (rather than masked) by a very simple approach that avoids additional installation, cost, maintenance, etc.
As with most issues, there is more than one answer or approach. In that spirit I offer this approach that has served us well. Since this post last June, we put 57 days/nights on Seaquel including a 17-day trip to Desolation Sound, and continue to have success with eliminating the holding tank problem. So we are now 3 years into this approach, with no investment in a filter, no hassle to install, no additional maintenance to change out filters annually, etc.
Good luck, and happy to answer any other questions regarding this alternative approach!
Here is a link to last year's posting, with the text below that:
posting.php?mode=quote&f=2&t=7625&p=63804#preview
Preview: Re: Holding tank vent filter
Seaquel wrote:
I will offer an alternative perspective on addressing the all-too-common issue of holding tank odor. When we purchased our then 2-year old R27, we inherited not only a reeking holding tank; but also a stench that had lingered inside the boat as well. Like most, my initial action was to install a filter system. However, anything that adds ongoing maintainence and cost gets extra scrutiny before I add it to my boat, and I did some research around CAUSE of the issue rather than the SYMPTOM. My findings:
A) Purchased the small book, "Get Rid Of Boat Odors" written by Peggie Hall, AKA "The Headmistress". Available on Amazon for $9.95. Best ten bucks you'll ever spend!
B) Stopped using my old holding tank treatment chemicals which were not working. Purchased "Odorlos", a holding tank treatment that adheres to the principles espoused in Peggie Hall's book, which is to utilize oxygen as a solution rather than a problem. Think about it: when you add a filter to your waste system you are trapping (masking) the problem. Instead, this is how Odorlos works:
"Provides naturally occurring bacteria with a continuous supply of the best alternative energy source to pure oxygen - nitrates." A 6 lb. tub costs $21.34 at Amazon, and for our 30 gal. holding tank one treatment is about 2 oz., so each tank treatment is literally pennies ($0.22/oz. = $0.44/tank).
The other learning is that leaving any saltwater in the holding tank provides a breeding ground for bad, smelly bacteria. This part is intuitive: saltwater contains all kinds of living organisms that, left in the tank in between boating trips, breed and/or die and begin to stink. Previously, after emptying the blackwater from the holding tank I would pump back in a gallon or two of saltwater (either from the toilet and or from the aft spraydown nozzle) and add the old type of treatment to this. Left alone in between boat usage (with no waste transferred from toilet to holding tank) the tank would begin to stink. That's right, without even adding waste - which is a big clue as to the root of the problem.
Now, here's what I do instead: after emptying the holding tank (and flushing with salt water a couple of times to ensure tank is relatively clear) I add two small scoops of Odorlos directly into the toilet. I then add one gallon of FRESH water into the toilet bowl and flush into the holding tank. That's it.
However, don't be too thrifty with flushing the toilet while on your boat. If you "short-flush" only enough to move contents from the bowl, but not enough to TRANSPORT contents from the toilet through the hoses and all the way into the holding tank you invite the problem. That's because another cause of odor is leaving contents in the untreated hose and not reaching the treatment center (holding tank). The "cost" of filling up your holding tank a little sooner is well worth it compared to managing odor that has permeated your hoses.
Results: not only is the old stench gone, from both the tank and throughout the interior compartments, but it has never returned. We are are well into 2 years on this system and it has worked to perfection, and no additional installation or filters to change out perpetually. I would have shared this sooner, but in fact wanted to go a long enough period to prove the results worked and were not temporary. I'm now convinced enough to recommend this approach without any reservation.
