4788 Holding tank vent filter-gctid348425

[cosmo777]

After upsizing to a 4788 this December and starting to get to know her, my first question is a quizzical one. I'm sure there'll be more in due time....

After getting some holding tank smell inside the hallway and the salon when using the vacuflush, I started digging into things.

I found there was a holding tank vent filter installed (since been replaced) behind the access panel at the side bar.

Oddly it was installed in the vent line that comes from the vented loop for the direct overboard discharge (which bypasses the holding tank via the wye valve)

When I checked the vent line from the top of the holding tank, it went directly to the thru-hull vent

The vent was fully plugged, causing the backup of air and the smell.

I've since replaced both thru-hull vents and re-routed the vent lines so the holding tank vent goes to the filter.

And the vented loops goes direct to the thru-hull vent.

So problems have been solved....

But I'm curious - Any reason to have the holding tank filter in-line with the vented loop rather than the holding tank vent line?

Not sure if a vent filter is standard for the 4788 or if it was an after-market install.

Either way, seems to me the factory or the after-market installer tapped into the wrong vent line.

Thoughts?

[mmichellich]

Why is any filter needed? Not from factory that way. Get chemicals that include formaldehyde and your problems are solved.

[Guest]

The filter you found - did it have charcoal in it (or something similar) or was it a foam element? Some vented-loops come with a foam element that keeps water from spitting out the vent when the loop is in use.

I bet the smell was due to the real vent being plugged.

[WhiteRockMike]

Hmmm - here's a few comments on the issue:

We've tried various ways to reduce holding tank vent odors during flushing (including a larger diameter vent line to make it more aerobic, various holding tank treatments including "Odorlos" enzyme type treatments and the "blue stuff") but the only effective way for us was the use of the charcoal vent filter. It totally eliminates the problem. With that said we haven't tried formaldehyde based tank treatments recommended by mmichelich as they don't seem to be sold around here anymore (at least we can't find them).

On our direct overboard discharge hoses that go from the wye valve to the above-waterline thru-hull, there is no vented loop - just a straight run of hose. Does yours discharge below the water line? We don't have vacuflush - just the standard Jabsco "quiet flush" electric macerator toilet. I don't know if this makes any difference.

Actually we've never used this direct discharge - indeed we removed the wye valve from the master head to holding tank line when we replaced it a few years ago. When we did this we just capped off the direct discharge line that went to the side thru-hull. We still have the wye valve on the guest head line, but have it closed and locked, and haven't used it, but it's there for emergencies.

[MerlinV]

We also have a charcoal vent line filter, but truthfully, it never occurred to me to check which vent line its in the middle of!

I did find out that it would sure be handy to have two elbows per arm to remove and install it from behind the panel in the wet bar though -I wonder when these started to be included from the factory - our 490 is 2003, and our friends boat which is a 2000 4788 also had one fitted as standard.

[Guest]

The activated carbon filter is part of the Vacuflush "system". To create the vacuum, you need to move a lot of air. That air has been sitting over the waste in the holding tank. Even if it had been chemicalized, a practice to which I do not subscribe, it would stink.

You NEED the filter. Your neighbors need you to have one.

It does get used up and you do need to replace it periodically. It can be home made if the cost of about US$75 each is prohibitive.

[cosmo777]

The way mine is installed, I'm pretty sure its a factory installation and it was installed in the wrong line.

It was a charcoal filter and I've since cut it in half, glued on fittings and charged it with new charcoal. Replacement cost was about $15.

It is surprising how well the vent filter works. No smell no more...

[Guest]

cosmo777 wrote:
The way mine is installed, I'm pretty sure its a factory installation and it was installed in the wrong line.

It was a charcoal filter and I've since cut it in half, glued on fittings and charged it with new charcoal. Replacement cost was about $15.

It is surprising how well the vent filter works. No smell no more...

Well done PAT...you have nailed it.

According to your first post, it is obvious that someone has misplaced where the filter should be. It should never be in the direct overboard discharge...it would be ridiculous to try to filter crap intended to be discharged overboard.

If the vent line is free and the holding tank stinks, the smell will be outside the boat.

If the vent line is clogged and the holding tank stinks, it will permeate inside the boat due to crap in the scavenge lines.

If the tank is well vented and deoderized it may not smell at all.

If the tank is suspect it is best to filter the odor from your moorage pals the way you have described...I do the same with DIY filters and aquarium charcoal....cheaply.

If the toilet smells after flushing it is probably nothing to do with what has just happened, but a problem with input water. In the vacuuflush and onboard freshwater flush...this problem is eliminated.

[Uncle_Bob]

My 2001 3988 with vacuflush has no "Y" valve from the factory. Cosmo has vacuflush, an in line filter in the wrong spot and a "Y" valve. Is it possible the vacuflush was a retrofit and the installer put the filter in the wrong line?