Holding tank filters

[US1Fountain]

Are all the Sealands holding tank filter bodies themselves the same size, except for the ends for the different size hoses? Needing more air volume to pass thru for when pumping out. I currently have the 3/4", considering the 1" filter, but only if it will flow more air thru it. Haven't been able to find any specs on the different filter sizes as far as free flowing volume capacity.
Thanks

[HopCar]

If you want more air to get into your holding tank, remove the filter. They tend to cause more problems than they solve. You want as much air in the tank as you can get. As I understand it, the bacteria that grow in the presence of oxygen do not create bad smells but if there is little oxygen, the type of bacteria that grows does produce a stink. There are even systems that pump air into holding tanks like you would a fish tank.
I recommend you get the book Get Rid of Boat Odors by Peggy Hall. She covers this in depth.

[US1Fountain]

I wish it was that easy. With no filter, it can be obvious at times. The thru hull is straight up 2 ft from the holding tank, not the recommended location for it to work odor free according to Peggy, and my sense of smell. Being in a covered slip with neighbors just feet away, odors, even the slightest, is not acceptable. So a filter does address that with flying colors. My problem is that the filter is too much of a restriction when pumping out, that my tank will suck in a bit. Trying to avoid that condition by getting more volume to flow into the tank during pump out, w/o installing a second filter and thru hull. When I removed the filter to see if the 3/4 (or 5/8) line is large enough to prevent this from happening, it is. So thinking a bigger filter will be less restrictive. However, I'm just thinking the only difference is really only in the ends for the hose connections???? Can't find any specs.

Have considered installing a new larger thru hull right above the tank, which is next to hull side, but if it doesn't control the odor 100% w/o a filter, then I have an extra unneeded thru hull. A buddy had a 1" thru hull for his vacuflush and his still stunk, so a little leary at this point to break out the hole saw. I prefer not to test by drill holes. A larger flowing filter will fit my needs, if in fact it is larger.

Tried a different chemical from our marina that was supposed to control the odors, (forget the name) worked for a couple weeks, then it stunk every time the toilet was flushed. Just used a few cap fills at a time. Had to put filter back inline in mean time.
Thanks

[peghall]

It's highly unlikely that a "couple of capfuls at a time" of ANYthing would do any good unless that much were added to every flush.

Try using a product called Odorlos without a filter in the line. Used ACCORDiNG To DIRECTIONS, it has an excellent chance of eliminating odor altogether. It's available from RV supply stores for a lot less than marine store prices.

If it doesn't we can investigate ways of increasing oxygen to your tank.

[SailFastTri]

if your filter is clogged the size matters little. Change it.

[US1Fountain]

Thanks. I'll search for that product.

The chemical I tried last yr required the tank to be flushed thoroughly and repeatedly, then approx 12 cap fulls on initial use. (I maybe wrong on the exact number, other than it was measured by the capful).
From then on, was only supposed to pump out the tank once and quit, leaving some matter/bacterial in, w/o filling with water and flushing till clean water appears as normally do. Then dumping just 6 cap full in.
By flushing with clean water each time, that would be re-establishing the environment for the system to work order free. By not flushing and just adding the 6 caps, you are just maintaining the environment. I'll get the name this weekend.

Have always used the blue stuff and been fine, but my gut feeling is with the filter in use, chemical or no chemical use would have had same no odor results.


Tank has always sucked in since filter was installed new.

[HopCar]

Odorlos does seem to be a favorite of my customers.

Peggy, What's in those filters? Is it just activated carbon like they use in aquarium filters? If so, it probably wouldn't be hard to make a filter of any size you want with PVC pipe fittings.

[peghall]

It's just activated carbon...and a whole bunch of people make 'em, though no one has had much success in marketing 'em to compete with SeaLand.

Filters only treat the symptom...they don't solve the problem--in fact, they actually help to CREATE the problem by impeding the free exchange of air via the vent line...as USFountain noted, pumping out tries to implode his tank. So using a vent line filter can be compared to doing nothing but for appendicitis but taking Tylenol for the pain. They also make it impossible maintain the vent line with regular back flushing to keep it clear, 'cuz if a filter gets wet, the charcoal swells and blocks the vent entirely....making filters a REALLY bad idea on monohull sailboats that spill waste out the vent when heeled. And, filters are expensive!

So all things considered, it makes a whole lot more sense to me to prevent odor from occuring in the first place than it does to just keep trying to trap it. That's not nearly as hard to do as most people think it is.

[Dockhead]

Can you remove or bypass the filter just at those moments when you're pumping out? And when you're at sea?

You could install a Y valve and a second vent outlet. Or if the filter is accessible, just pop it off.

The experts here are right, of course, about curing the disease, and not just the symptom, but you seem to be happy with how your filter works except when you're actually pumping out, which can't be more than 0.1% of your time on the boat.

[peghall]

By the time he did all that, he could re-plumb the vent to provide enough oxygen to the tank to do away with the filter.

[US1Fountain]

Here's the product I am currently trying. Unique Natural Products Marine Digest-It

Unique Natural Products — Marine Digest-It


My filter is only accessible by removing a side storage compartment, to access the holding tank.

With my vent fitting being located approx 2' directly above the tank, is there a way to use it so as I don't have to drill another hole? I know the vertical height is my obstacle at this point, not sure if there is a work around.

Thanks

[sailorchic34]

Me I would make a short and wide filter using PVC pipe and fittings, a small bit of screen and activated carbon from a tropical fish pet store... No glue required....

Going for a two inch wide by oh 3" tall would be better then the long narrow things being sold today. You still need to maximize the free area inside to keep the pressure drop low and you get that by a larger diameter....

[chrisjs]

When we ( I mean "I") pump out I remove a 3/4 inch plastic plug in the air vent line between the tank and the charcoal filter. It is in the same general area as the pump out thruhull valve. Easy to install something similar if you do not have an appropriate fitting. Lets plenty of air flow in to the tank during pumping and easily replaced afterwards.

[peghall]

Whose idea was that??? I think I know why--to prevent tank contents from spilling into the vent line--and therefore the filter--when the boat heels. But it's VERY bad idea!

There shouldn't be any plug in ANY vent line, whether it's on water tank, fuel tank or waste tank, or whether there's a filter in the line or not.

Tank vents provide both a source of air to replace contents as they're drawn out (for a waste tank that's during pumpout or dump at sea) AND an escape for air in the tank that's displaced by incoming contents...iow, each time the toilet is flushed. If air can't get out, the tank becomes pressurized. And when tank becomes pressurized it can cause any one of a number things to happen, all of which are very nasty and unpleasant.

Besides, if you're gonna prevent any air/odor from going out the vent, why are you wasting money on a filter?

[chrisjs]

I think there was some misunderstanding. The "cap" does not close off the vent line - it closes a separate port into the vent line between the vent filter and the tank.
I understand fully that the best way to solve the "stink" problem is by getting more air to the tank. Unfortunately, like many others, retrofitting a larger diameter vent line is next to impossible without major boat surgery.
Not only does the vent line run pretty near horizontally in the bilge from the top of the tank, it then ascends about ten feet to exit from the dutch bridge forward of my pilot house. Hence, as with others, we resorted to using a filter to provide a little relief to out dock neighbors, full aware that it is a compromise at best.
The "plug" that I am referring to was installed when I did manage to increase the diameter of the horizontal run to a 1.5 inches and installed the vent filter. Removing the plug allows the tank to vent more easily during pump out. It is normally screwed in place. I have not noticed any significant smell or any seepage when it is removed temporarily during pump-out. It is above the level of the tank, though conceivably if the tank were overfilled so that waste intruded up the vent line, removal could result in leakage. The other function of the cap is to facilitate back-flushing of the vent line into the tank.
Sorry if this approach offends but it works fine for me!! Also, we do not "heel" because we are a stabilized trawler!!