Another holding tank vent question

[boaterholic]

I have started getting holding tank, smells inside the boat over the last few days, I’m sure, because the two heads were being used while the boat was being delivered to its new home.
I am suspicious of the vent line. Can anyone tell me if I disconnect the line from the through hall? Should I be able to blow backwards into the tank without restriction?
I have tried removing the charcoal filter from the line, and it is not plugged up as I can blow through it in either direction. Also, I can blow through the line and out the side vent where it would normally vent. However, if I try blowing through the line and into the tank, I cannot blow into the tank. I assume this is not normal as I would imagine when you are being pumped out, he needs to be able to vent into tank.
I can access the vent sitting on the top of the tank. But before I did, I wanted to ask here on the forums, if that would be the next step in troubleshooting.
Thank you

 

[O C Diver]

If you can reach the vent easily, it's a good practice to push a little water from a hose to make sure the line is clean after pumping out.

Btw, loose the charcoal filter. The stuff in the tank needs air (oxygen) to break down. The filter blocks the flow of air.

Ted

 

[boaterholic]

The vent fitting not particularly easy to get to. But for maintenance purposes I can access the tank fittings and line connections.
My plan is to remove the filter.
But first thing I need to find out if not being to blow air into tank via vent line is causing my issue. I think I should be able to blow air into it; I can’t imagine a check valve in the vent fitting, if someone can confirm before I remove the fitting from the tank.
Thanks

 

[READY]

My guess is the vent line is blocked right where it enters the tank. Not an expert but I would not think there would be a check valve in a holding tank vent line. Perhaps if you share year, make and model of boat another owner could comment.

 

[boaterholic]

My apologies, I should have included that info.
New to me 2007 Jefferson 52 Pilothouse.
Holding tank is between the two cabins, dead centerline, under companionway.

Would you recommend before I removed the fitting from the tank to pull the hose off and try a coat hangar going down? It’s a soft radius 90 degree fitting.

 

[HopCar]

When you remove the filter you’ll need to change the hose. That should eliminate any blockage in the hose. Stick a probe into the tank where the hose fitting is to be sure the blockage isn’t there.

Trying to blow into the tank through the vent is like trying to inflate a rigid balloon. I don’t think you could blow much air in that way.

Sewage odor in a boat often comes from old hoses that have become saturated and need to be replaced. I think Peggy addresses that in her book.

 

[boaterholic]

I’ve been doing the “paper towel wipe test” on the hoses an old timer told me to try.
On my previous boat I could smell a little on hose between one of the vacuum generators and holding tank.
This one so far is not smelling when I check the hoses, which look really clean like new.
I’ll remove the short piece of vent line that was between filter and tank to verify that section not blocked. Then probe into rank via fitting. I know you said it’s hard to blow much air into tank, but I could not blow any at all no matter how hard I tried.

 

[Comodave]

Ok, first thing is to get rid of the vent filter. You said you were going to do that so good. The filter can easily get plugged up.

Then you should, ideally, add a second vent from the other side of the boat. Also increase the size of the vents so you get good air flow through the tank. The smell is from anerobic bacteria. It really stinks. Aerobic bacteria is good and doesn’t stink so if you get lots of air into the holding tank it won’t smell. I have 2 1.5” vents to my tank and get no smell. Or add a bubbler system in the tank to get air into the tank.

The other thing to check is the discharge hoses, typically 1.5”. The way to test them is get a clean cotton rag and wet it with hot water. Lay it on the hose and let it dry. Then take it out and smell the rag. If the rag smells the hose is bad and needs replacing. I only use Raritan SaniFlex hose. It is extremely flexible and therefore easier to install. It also doesn’t permeate the smells.

 

[boaterholic]

Update:
Yesterday late afternoon I took the hose off the fitting. I could blow out with no problem, so entire length of hose was fine.
I took a screwdriver and probed into fitting. It barely was in before hitting a block. I rotated and dug out some of the blockade. Looked like old wood dust coming out. I then took a wire coat hanger and straightened it out. Started to poke and dig out more and then the wire came out a corrosion hole in the bottom side of fitting just past where the hose would have stopped.
So at that point I removed the fitting and took back to my garage. Finished clearing out the fitting inside and then with my angle grinder with wire wheel cleaned the outside really well. Stuck a piece of painters blue tape on inside of hole area, mixed up some JB Weld and filled in the hole.
After it set up I removed the tape and took fitting back to boat. Cleaned the base for fitting that is mounted on tank best I could. Put some fresh sealant around the base of fitting and re installed. Put hose back on but slid the hose clamp a little further back from end to make sure and not put clamp force on the repair.
Cleaned up the area and sprayed a little Odoban around the area.
Now airing out the boat a couple days and hope the smell goes away.
I have to assume previous owner let tank overfill before pumping out and that was the blockage. It’s a wonder there was not system damage with pump outs or overboard pumping when it was offshore.
Hopefully all will be good now.
Thanks for the help

 

[READY]

Nice you found the problem. Sounds like it sat overfilled for awhile. FYI I switched to fresh water flush abd that does wonders for eliminating tank and bowl odors and also eliminates another source of corrosive saltwater onboard which also minimizes the mineral buildup in the hoses. As mentioned, in the future run some water down the vent line from time to time and it should not reoccur.

 

[HeadMistress]

The two most likely places for a vent blockage are the vent thru-hull and the other end of the vent line--that end of of the hose and the vent fitting on the tank. Clean the vent thru-hull fitting...use a screwdriver blade, Icepick or whatever works.. Better yet, replace the "vent" thru-hull with an open bulkhead (aka "mushroom") fitting that will allow you to put a hose nozzle against it to back flush the vent line every time you wash the boat and/or pump out to prevent future blockages. But first, replace the vent line, straighten the run if necessary, and get rid of vent filters. An open thru-hull and a short straight vent line that allows air exchange with the gasses in the tank will go a long way in preventing odor from occurring in the tank, making any second vent line unnecessary.

--Peggie

 

[boaterholic]

Nice you found the problem. Sounds like it sat overfilled for awhile. FYI I switched to fresh water flush abd that does wonders for eliminating tank and bowl odors and also eliminates another source of corrosive saltwater onboard which also minimizes the mineral buildup in the hoses. As mentioned, in the future run some water down the vent line from time to time and it should not reoccur.

Luckily my toilets use freshwater not seawater.
I’m checking on the hoses next for smell and see if I need to replace them or not.

 

[boaterholic]

The two most likely places for a vent blockage are the vent thru-hull and the other end of the vent line--that end of of the hose and the vent fitting on the tank. Clean the vent thru-hull fitting...use a screwdriver blade, Icepick or whatever works.. Better yet, replace the "vent" thru-hull with an open bulkhead (aka "mushroom") fitting that will allow you to put a hose nozzle against it to back flush the vent line every time you wash the boat and/or pump out to prevent future blockages. But first, replace the vent line, straighten the run if necessary, and get rid of vent filters. An open thru-hull and a short straight vent line that allows air exchange with the gasses in the tank will go a long way in preventing odor from occurring in the tank, making any second vent line unnecessary.

--Peggie

Thanks for the info Peggie.
I temporarily re installed the filter as I had to leave out of town for rest of week. But next week when I return home I plan to remove the filter, and if the hose is not permeated thru on smells, check if it is long enough to reach the fitting. If it is not, I can get a brass nipple to connect the two ends together and do away with the filter.
Thank you

 

[boating rich]

I followed Peggy’s advice in her book and had a larger straight vent tube to a trough hull so that air can free go in and out. Best thing I have done. It worked great. I had to fight with the yard since they were convince I was crazy

 

[AlanT]

Glad that you solved your problem. I did not see whether you are flowing fresh or sea-water. I have used fresh on my last 3 boats - no smells.

 

[Bmarler]

I use only plastic or bronze fittings on black water plumbing. Preferably plastic. No corrosion. I’d be replacing that patched tank fitting when you remove the filter.

 

[boaterholic]

Glad that you solved your problem. I did not see whether you are flowing fresh or sea-water. I have used fresh on my last 3 boats - no smells.

Fresh water

 

[boaterholic]

I use only plastic or bronze fittings on black water plumbing. Preferably plastic. No corrosion. I’d be replacing that patched tank fitting when you remove the filter.

I have plastic fittings that would work but was concerned odor would permeate through cheap plastic sooner than brass.
The fitting replacement I am trying to find right now. But would prefer it was the same so as not to make a bigger project

 

[HeadMistress]

Thanks for the info Peggie.
I temporarily re installed the filter as I had to leave out of town for rest of week. But next week when I return home I plan to remove the filter, and if the hose is not permeated thru on smells, check if it is long enough to reach the fitting. If it is not, I can get a brass nipple to connect the two ends together and do away with the filter.
Thank you

Do NOT use a brass--or any other metal--nipple anywhere in sanitation system plumbing including a tank vent line..use a PVC "hose mender" (short piece of PVC pipe that has the same OD (outer diameter) as the ID (inner diameter) of the hose you're "mending." Actually , with one exception--a ship'sbell--brass has no place anywhere on a boat!

--Peggie

 

[boaterholic]

Ok I didn’t know. And I assume that includes bronze and stainless then? I only ask because I think the vent fitting on the tank is stainless, and the thru hull is either stainless or chrome over something.
Thank you

 

[HeadMistress]

Brass is the only real no-no...it's a mixture - not a compound - containing copper and zinc. The zinc will dissolve over time allowing bad things to happen. Bronze is the best choice for for thru-hulls, lasts for decades, but VERY expensive. Stainless steel and chrome plated metal are ok for thru-hulls, but not a good choice as tank fittings that come in direct contact with sewage 'cuz sewage is corrosive. I've NEVER seen a bronze tank fitting on ANY tank--water,fuel or waste, only nylon or PVC. Never use nylon for thru-hulls, above or below waterline...above waterline is a no-no because it's not UV resistant...sunlight turns 'em into powder. Marelon is the only plastic safe to use for below waterline thru-hulls.

--Peggie

 

[boaterholic]

Brass is the only real no-no...it's a mixture - not a compound - containing copper and zinc. The zinc will dissolve over time allowing bad things to happen. Bronze is the best choice for for thru-hulls, lasts for decades, but VERY expensive. Stainless steel and chrome plated metal are ok for thru-hulls, but not a good choice as tank fittings that come in direct contact with sewage 'cuz sewage is corrosive. I've NEVER seen a bronze tank fitting on ANY tank--water,fuel or waste, only nylon or PVC. Never use nylon for thru-hulls, above or below waterline...above waterline is a no-no because it's not UV resistant...sunlight turns 'em into powder. Marelon is the only plastic safe to use for below waterline thru-hulls.

--Peggie

Ok.
I’m searching for replacement tank mounted fitting that is same fit so I don’t have to come up with a big project to start from scratch. This fitting on my holding tank has a base flange approx 2 1/2” with four holes. It mates to what looks like a permanently installed base on tank that has four bolts sticking up, and a thick rubber gasket that kind of looks like a garden hose flat oring but a little larger diameter. My fitting drops onto that and held by four lock washers and nuts. Fitting is shaped with a long radius 90 degree sort of like a street elbow for house plumbing.

 

[Bmarler]

Maybe something like this? 3/4" Sch 80 PVC Van Stone Slip Flange 854-007

Plumbing flanges are usually standard sizes, so the pipe size determines the bolt pattern.

 

[SteveK]

A picture sure may help. If I understand the nipple on this has failed. If I am correct, can you drill the hole bigger to accept a plastic mushroom thru hull with the correct vent hose size, then bolt down as before.

 

[boaterholic]

Maybe something like this? 3/4" Sch 80 PVC Van Stone Slip Flange 854-007

Plumbing flanges are usually standard sizes, so the pipe size determines the bolt pattern.

Interesting. I’ll have to get the true dimensions to compare.

 

[boaterholic]

A picture sure may help. If I understand the nipple on this has failed. If I am correct, can you drill the hole bigger to accept a plastic mushroom thru hull with the correct vent hose size, then bolt down as before.

I’m away from boat till Sunday night so I can’t get a picture. But in my search I have seen a similar fitting from Vetus. Let me see if I can get a picture of it on here.

 

[boaterholic]

Very close to this one from Vetus. Mine does NOT have the bell shape at base and whatever is inside there. Mine is just straight to the flange, with a similar long radius.

 

[HeadMistress]

You're WAAAY overthinking/overproducing what should be a very simple project. You'll want to enlarge the vent to 1"...so get rid of the assortment of pieces you have now and use a hole saw to enlarge the hole in the tank that's the right size to accommodate Uniseal UNISEAL (which is essentially just a rubber grommet that's used extensively for this type of project and do not leak unless the hole isn't round and will cost you about $3.50) that's the right size for a 1" hose fitting. The folks at Uniseal are very helpful and will make sure you get the right one and provide detailed instructions. Use good quality 1" sanitation hose for the vent line and anything but brass or nylon for the vent thru-hull. And I'll be glad to help you do it right.

And btw...you'll never be able to blow air into a tank through the vent line.
All tank vents have two main functions: to provide an escape for air displaced by incoming contents and provide a source of air to replace contents as they're pulled out. When air displaced by incoming waste cannot escape out the vent the tank becomes pressurized, creating increasing back pressure that prevents the toilet from flushing.

Without a source of air to replace contents as they're being sucked out of the tank, the pump will pull a vacuum that'll prevent it from pulling out more than a gallon or two. A particularly strong pumpout can even implode a tank.

So pushing air into the tank via the vent line just creates a blocked vent line.

--Peggie

 

[boaterholic]

Ok I’ll look into that. Thank you for the helpful info too!
As far as blowing air in, I now can blow air in but as soon as I took my mouth off the hose it came right back out as expected due the reasons you stated. So at least I now have proof no blocked vent as it was before.