Holding Tank Filter DIY Questions

E

estebanj

New Member
Apr 2, 2007
590
South Florida
Boat Info
260 Sundancer
Engines
350 Merc
I did the mod today to be able to refill the filter myself. I cut the filter and used a "no-hub" to join.

My questions are:

* Does any active charcoal work? I got the one for aquariums at Wal-mart.

* Does the size of the charcoal pellet matter? The ones from the factory were small cylinders. The Walmart kind is more like gravel.

* How full should it be? Should it be packed tight with charcoal or leave some room for air to more easily flow?

* I know it cannot get wet with holding tank sewage, but what about some water coming from the through hull side? I don't know how it got there, but there was a tiny amount when I took off the hose.

Thanks,

Esteban
 
I've rebuilt mine twice....granulated vs rod charcoal - no problem...I wouldn't pack it tight, just pour it in & let it settle natually. Don't know about fresh water contact.

When it seems not to be working I rebuild...I try & pump as soon after the 1/2 full light comes on...someone posted the lights are not too accurate thus the tank might be well over 1/2 when the light comes on.
 
Charcoal

Wet charcoal can't filter air.

I suspect you are getting some condensaton, but might want to seal the joint of the two sides of the modfied filter with teflon greast when reassembling.

The resason "rod" charcoal is used is to lessen hard packing to maintain airflow. Granules are typically smaller and more irregular in shape thus will pack more densely and slow the passage of airflow. Its a catch 22, leave it loose packed and the charcoal will settle verticlally inside and the gases will pass over the filter media, pack too tight and it becomes a plug.

Using granules, I would seem best to vibrate the fill a little to allow some settling and refill, but don't ram pack it.
 
Is this filter in the vent line? I'm about to plumb a holding tank and this is the first I heard about a holding tank filter. :)
 
Yes, it goes in the Vent Line. Made by Seland/Dometic. It's basically a 2 inch PVC pipe about 12 inches long with a fittin on each end, one into the tank and the other into a hose that goes on a through hull.

The inside has a "sponge" membrane on each end, and between it's filled with activated charcoal.

The price new is $50-75 depending on source. Many people have cut the filter in half to do DIY replacements with new charcoal. They recommend changing once a year, or if it ever gets wet.

Some people don't like them b/c they feel it restricts the air flow in the vent line.

I've had mine 6 months and like it. I never have sewage smell from the tank.

Esteban
 
Thanks Doug! I'll definitely be making one of these this winter.

I was struggling a bit for smaller projects. The wakeboard..err... radar arch project that I bought from Kendor has me a bit overwhelmed, and I'm still at the point where I'm spending a few minutes every day looking back and forth from the arch to the boat wondering how exactly I'm going to get it up there and temporarily in place in order to engineer the small modifications that the mounts need to fit my boat. :)
 
It is not recommended to "rebuild" your vent filter. As you have all stated, if it gets wet it will not pass air. This causes the holding tank to be pressurized. I have seen tanks explode, fittings be blow out and no longer will you be able to pump out . You must have air flow to pump out. I have seem many tanks collapsed due to "rebuilding" the vent filter. Yours will work, but there is a reason they use the type of charcoal they use. They recommend replace every year, that is a little unreasonable at the price. The bottom line is, they last for years as long as they don't get wet. Wet means by any kind of water. If they have not gotten wet but you start to smell odor. This means the charcoal has settled, simply remove it, shake up and reinstall it. There will come a time when they just stop working, then replace it. Check out www.marinediscounters.com for the best price.
Thanks
Brad
 
Brad,

My filter has filled with water twice this season. I am pretty sure that it is due to sea water coming back in through the vent outlet. I notice that SR installed the vent line in such a way that the vent does not loop higher than the through hull fitting. Is there a Sealand specification for the height of a vent loop?
 
Sea Gull said:
Brad,

My filter has filled with water twice this season. I am pretty sure that it is due to sea water coming back in through the vent outlet. I notice that SR installed the vent line in such a way that the vent does not loop higher than the through hull fitting. Is there a Sealand specification for the height of a vent loop?
Click to expand...

I installed a Perko Vent Cover over my vent with the opening facing the transom. The installation looks like it came that way from the factory. :grin: On the 260DA, the vent is located way too low on the side of the boat so when comming off plane or when you have a load on board I think water can get in there. Also my sump outlet is installed right next to the vent outlet and I had water feeding back into the bilge when I had a bunch of people on board even though that was a looped line. Here is the cover I installed............it's a perfect fit over the standard Sea Ray vent fitting.

317260040.jpg

Here's is a link to Boater's World site for the fitting.

http://www.boatersworld.com/product/317260040.htm
 
Sea Gull said:
Brad,

My filter has filled with water twice this season. I am pretty sure that it is due to sea water coming back in through the vent outlet. I notice that SR installed the vent line in such a way that the vent does not loop higher than the through hull fitting. Is there a Sealand specification for the height of a vent loop?
Click to expand...

No, Sealand really doesn't have a spec for vent loop hieght but I usually make it around a foot.
 
Brad,
That is definitely the best price I've seen on the filters. I am curious whether a wet homemade filter is any different than a wet store bought filter. Maybe we should have a whistle that makes noise during pumpout. No whistle sound then you're in trouble. I usually listen for the whooshing sound when pumping out.

I had moved my vent line and thru hull from its location near the aft cabin because that hose would get stinky rather quickly and added odor to the aft cabin. I had no luck finding sanitation type hose to fit the Todd holding tank vent fitting. I could only find corrugated bilge pump type hose.

Eddie
 
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