97 405 Aft Holding Tank Odors/Venting

[ndunlop33]

My marina seems to have a hard time emptying my aft tank so I’m getting a bad odor. They think it’s because there is one vent for the 2 tanks. Does/has anyone else had this issue? If so , any suggestions for how to fix this? I find sometimes when I flush some odor escapes inside the cabin so maybe have air leaching and preventing them from pumping it out empty? Any help would be greatly appreciated!! Thanks

[bud37]

Generally there is one vent per tank....why do they think there is only one vent ? Check for vent filters, they need to be refreshed to keep from blocking air passage thru, especially if they get wet, spiders etc.

Hopefully someone with the same boat can chime in here for you.

[tomschauer]

each tank has it own vent. If they can't fully empty the tanks, you may a sludge build up that needs to be removed from the tanks.

[g36]

A 405 does have a vent for each tank and there is no carver installed filter in the vent lines. If there's a smell you can be sure the hoses if oem are odor saturated mine were for sure with that age... on my 405 I replaced them and the long run in the engine room and a couple places a used pvc pipe.and good flex sanitation hose. I would also unscrew the tops of the tanks which are easy to get to and stir up the sludge go pump out and do it again a couple times. Maybe gross but you can be sure whats in there mostly gone. There will be no way ever to completely pump out there will always be some left. I also use a noflex digest product that helps alot. In case you didn't know
Your fwd holding tank is port side under dinette cushion nearest midship. And aft tank access is at the foot of the bed in aft cabin

[g36]

One thing since both discharge deck plates are midship port side you'll notice its a pretty long run through the engine room to the aft holding tank in the aft cabin. As I mentioned earlier youll never completely pump out a holding tank and this one will also hold some fluid in the long run through the engine compartment no matter what you do. I often dump some clean water back trough the deck ports after a pump out . Maybe doesnt help much. just something I've always done.

[ndunlop33]

Thanks for the replies. I don't know why the pump out guys at my marina think there is only one vent. They did say when they pump it out that they only remove one deck cap at a time because there is only one vent. I don't know if this makes sense to you all ??? There were no inline filters on the boat. I had one installed hoping this would help but it really hasn't stopped the problem. The person I bought the boat from changed all piping to pvc at some point. I have also started using the Noflex Digest so I'm hoping that will help if there is a sludge build up. I will say that when I take the boat over to the pumpout station I don't seem to have a problem emptying the tank. It clears right out. Would this indicate that it's not a vent problem?

[g36]

Its good the previous owner changed that out.. When I pump out my 405 I undo both deck plates screw in an adapter for the pump hose in each one. Pick one and start pumping when it can't get anymore move it over. While that ones emptying I put some water back into the other and swap over and do the same with the other. Then Suck em best you can and done. You will have 2 vent lines they are 2 separate systems. If you can pump it ok then they're probably in a hurry and don't really care. Ill be at my boat this weekend If you want I'll post pics of the vents . Imo. The noflex works well just give it a chance if you just started.

[rjr]

Definitely give a plus 1 to Noflex. Has worked well on our boat. I happened to read the Vacuflush brochure recently (must have been raining) and it stated to add 5 gallons of fresh water once a month through the toilet. I assume this will help clean the lines, dilute the waste and potentially reduce odor.

[ndunlop33]

Ok, that's what I was thinking. Pics would be very much appreciated just in case I'm missing something. Maybe one is blocked as they tell me it doesn't pump unless one cap is on. I will continue with the Noflex and I very much appreciate everybody's help!

[tomschauer]

It shouldn't matter if on of the caps is on or off. If they have both caps off and the cap that's not being drawn through has suction, maybe, maybe the Y valve for your OBD system is not in the proper position.
I haven't looked at mine in quite awhile, but I do believe you could somehow combine the tanks, or the two pump out fittings at the y valves.