Holding Tank Odor

Stumped. Vent line (without filter) is clear, no visible leakage, hot rag test on all hoses pass the smell test (did replace one hose yesterday that did not...someone had used an exhaust hose on one short connection). Also laid hot rags on tank and they passed the test as well. Put hot rags on all tank connections too and they passed. But when flush either head, a waft of odor becomes very noticeable. Odor is not near either vacu-flush unit either...it is definitely around the holding tank area.
Seems like any "back pressure" created would go out the clear vent line. Odor dissipates (but does not go away) after a few minutes but with next flush is right back.
Ideas for further investigation? Thanks

What about a leak around the vent line at the tank? And do you get the same smell outside the boat at the vent when flushed?

dhays said:

What about a leak around the vent line at the tank?

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Thanks. That was one of the connections I also hot rag tested. Seems OK.

Can you put some low pressure air into the vent and spray soapy water around the holding tank and hoses and look for bubbles. You might try a shop vac to blow air into the tank. I would probably do a complete pump out first... Don't know if the joker valves would stop the air from coming back into the heads or not. If you can get a couple of psi air into the tank and soap it, you may be able to see where/if the tank or hoses are leaking.

Small crack in fitting

Off to the hardware store. Found a small crack in the fitting for the vent line to the holding tank. Problem identified, now just need to source the fitting and be a contortionist to replace it! Thanks all.

sum escape said:

Off to the hardware store. Found a small crack in the fitting for the vent line to the holding tank. Problem identified, now just need to source the fitting and be a contortionist to replace it! Thanks all.

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That could do it. The rag test will just tell you if the hoses are permeated. If there is an air leak, then you are venting some of the displaced air from the flush into your boat. Not a permanent fix, but I would use some duct tape around the cracked fitting to see if that eliminates the odor issue.

sum escape said:

Off to the hardware store. Found a small crack in the fitting for the vent line to the holding tank. Problem identified, now just need to source the fitting and be a contortionist to replace it! Thanks all.

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If your tank has standard fittings, you need a thread-barb fitting that will fit TIGHTLY in a 5/8" hose, Whether it should be straight or a 90 depends on what you have now. That's not something typically used in domestic plumbing, so you're far more likely to find it at a marine store than a hardware store.

Peggie
http://www.amazon.com/New-Get-Rid-Boat-Odors/dp/1892399784/
"If you can't explain it to a six year old, you don't completely understand it yourself." --Albert Einstein

Thanks

HeadMistress said:

If your tank has standard fittings, you need a thread-barb fitting that will fit TIGHTLY in a 5/8" hose, Whether it should be straight or a 90 depends on what you have now. That's not something typically used in domestic plumbing, so you're far more likely to find it at a marine store than a hardware store.

Peggie
http://www.amazon.com/New-Get-Rid-Boat-Odors/dp/1892399784/
"If you can't explain it to a six year old, you don't completely understand it yourself." --Albert Einstein

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Thanks Peggie, your book is on my Kindle! That's how I learned about the hot rag test.....thanks!

dhays said:

That could do it. The rag test will just tell you if the hoses are permeated. If there is an air leak, then you are venting some of the displaced air from the flush into your boat. Not a permanent fix, but I would use some duct tape around the cracked fitting to see if that eliminates the odor issue.

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The fitting broke as I was examining it....hose fell completely off. So tomorrow I'm off to find the correct fitting. Thanks.

Brass fittings at NAPA or similar, for less than boat store prices.

Please tell us about the "hot rag test" Thanks

kartracer said:

Please tell us about the "hot rag test" Thanks

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Peggies book has the details, but in short get some strips of clean rags, wet them with hot water, wrap suspect areas (hoses, connections, etc) with the hot wet rags, let them cool a few minutes, take off and sniff the cooled rags. Your nose will tell you if the odor is coming from that suspected area.

FF said:

Brass fittings at NAPA or similar, for less than boat store prices.

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NEVER use brass in any part of a sanitation system. It's not even recommended for use anywhere else n a boat with the possible exception of a bell.

Peggie
http://www.amazon.com/New-Get-Rid-Boat-Odors/dp/1892399784/
"If you can't explain it to a six year old, you don't completely understand it yourself." --Albert Einstein

HeadMistress said:

NEVER use brass in any part of a sanitation system. It's not even recommended for use anywhere else n a boat with the possible exception of a bell.

Peggie
http://www.amazon.com/New-Get-Rid-Boat-Odors/dp/1892399784/
"If you can't explain it to a six year old, you don't completely understand it yourself." --Albert Einstein

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Yes and someone should tell Grand Banks that too! That is what they used that failed! I found a replacement plastic fitting at Home Depot for $3.50. All is good now.

FF said:

Brass fittings at NAPA or similar, for less than boat store prices.

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And it will soon corrode. Plastic or nylon fittings would be much better in contact with sewage or corrosive vapors. We're talking two or three dollars here, not hundreds.

Another happy ending!

HeadMistress said:

NEVER use brass in any part of a sanitation system. It's not even recommended for use anywhere else n a boat with the possible exception of a bell.

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Most of our plumbing fixtures (faucets, shower handles, etc.) are made of chrome plated brass but of course they are only in contact with fresh, potable water just like they are on land. In many cases, they are the same as found in residential use.

Air horns are often made of chrome plated brass for some reason. I would think stainless steel would be better. It must be a manufacturing thing.

Brass should never be used in contact with sea water.

"Off to the hardware store. Found a small crack in the fitting for the vent line to the holding tank."

Most vent lines are seldom immersed in sea water.

De zincification requires immersion is why props go pink.

The OP stated the fitting was CRACKED , and fell apart .

A cracked fitting would be from abuse, overload ,perhaps installing the tank?

A std fuel line fitting will work as well as any. Plastic tank, rubber hose , no electric.

Might be interesting for folks at a marina to ask , what IS the source of their small 1/4 , 3/8, 1/2 inch parts in the bin display .

I like plastic fittings they work just fine. I have some of the schedule 80 grey plastic ones used on a seacock for splitting water to heat pump and a utility pump, bought them at Lowes. If say I managed to step on it and it broke, which it does not break, I could always turn off the seacock.

The schedule 80 black polypropylene fittings I think are better and tougher than schedule 80 PVC.
Got a 90* from Amazon cheap. I installed in the discharge line from head to the seacock. I pump out the waste into the water. My connection hose is that standard white PVC.
Examples here
Polypropylene Threaded Pipe Fittings Category | Polypropylene Pipe Fittings and Polypropylene Pipe Couplings. | U.S. Plastic Corp.

Might be interesting for folks at a marina to ask , what IS the source of their small 1/4 , 3/8, 1/2 inch parts in the bin display

The marine industry is too small a market for it to be profitable for any mfr to make fittings ONLY for the marine market. Marine stores buy them from distributors who buy from the same mfrs who make them for the plumbing, automotive and other industries, according the specifications needed for that industry. Some things can be "universal"...others must be industry--or even customer--specific. For instance, Moeller makes most of SeaLand's plumbing fittings, some of which are the same as those sold in hardware stores except for wall thickness or material--SeaLand's are heavy duty sched 80, hardware store version can be thin-walled sched 40 or thinner sched 80 made by anybody.

There are reasons for a carbon filter in waste vent lines.

And for all those with hot rags, it appears there must be problems or you would not be looking its location. Time to consider getting rid of smelly hoses; PVC pipe is permanent, mechanically strong (beware of fittings though) and stink proof.

On same topic .... We have two heads; forward is non exotic electric, aft head is a Jabsco manual. We have all new hoses & stainless holding tank.
When we use the forward head, all is fine, when we use the aft manual head, some odor appears towards the forward end of the boat. Of note: the forward head ( bowl ) drains empty ( not holding any water ) which makes me think that the fresh water after the flush just gravity drains into the holding tank. Is it possible that when I replaced the hoses, I should have left a loop of sorts to keep some water in this hose as a trap for vapor instead of running it sloped straight down into the tank ( the tank is about 12" below level of the forward head ) or is there something else I should be looking for . ? maybe install a check valve in the 1 1/2" discharge line ?

Any thoughts on this ... ? FB

Except for the all-china "thrones" with multiple flush options, marine toilets aren't designed to hold water, so the bowl draining into a tank that's below the toilet is a good thing. As for whether you should install a check valve in the toilet discharge, there should already be one in both toilets...it's the li'l cup-shaped gizmo with slit in the bottom and "lips" on the outside called the "joker valve." It should be replaced at least every two years in an electric toilet, every year in a manual toilet.

However, if odor were backing up into the bowl from the tank, you'd smell it coming into the bowl...that head compartment would stink. But that's not happening. Your only problem is odor "near the forward end of the boat" when the aft toilet is flushed. That tells me that the aft toilet is pushing odor out of something on its way to the tank. There are enough possible "somethings" that it's gonna take some conversation for me to figure out what that particular "something" is. Send me a PM with your email address and we can go from there to arrive at mutually agreeable day/approx time to spend about 30 minutes on the phone.

Peggie
http://www.amazon.com/New-Get-Rid-Boat-Odors/dp/1892399784/
"If you can't explain it to a six year old, you don't completely understand it yourself." --Albert Einstein

HeadMistress said:

Except for the all-china "thrones" with multiple flush options, marine toilets aren't designed to hold water, so the bowl draining into a tank that's below the toilet is a good thing. As for whether you should install a check valve in the toilet discharge, there should already be one in both toilets...it's the li'l cup-shaped gizmo with slit in the bottom and "lips" on the outside called the "joker valve." It should be replaced at least every two years in an electric toilet, every year in a manual toilet.

However, if odor were backing up into the bowl from the tank, you'd smell it coming into the bowl...that head compartment would stink. But that's not happening. Your only problem is odor "near the forward end of the boat" when the aft toilet is flushed. That tells me that the aft toilet is pushing odor out of something on its way to the tank. There are enough possible "somethings" that it's gonna take some conversation for me to figure out what that particular "something" is. Send me a PM with your email address and we can go from there to arrive at mutually agreeable day/approx time to spend about 30 minutes on the phone.

Peggie
http://www.amazon.com/New-Get-Rid-Boat-Odors/dp/1892399784/
"If you can't explain it to a six year old, you don't completely understand it yourself." --Albert Einstein

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Been there, done that. I purchased a plastic water filter assembly that accommodates a charcoal filter. Next put that in series with the vent hose. Prior to adding the charcoal filter, the stench would knock your socks off.

I made my own assembly because WestMarine's filter for this application was almost $100 and a throw away at that. Didn't allow one to change the charcoal filter contained in the product.

Giggitoni said:

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Just silly of course but better than popcorn

Been there, done that. I purchased a plastic water filter assembly that accommodates a charcoal filter. Next put that in series with the vent hose. Prior to adding the charcoal filter, the stench would knock your socks off.

So how would a vent line filter eliminate an odor that's inside the boat, not out the vent?

Peggy--

The ONLY thing I have found to eliminate inside stink is PVC pipe. Used it in my old sailboat and also in my Silverton 40 with great results. The vent filter will only improve the conditions that neighbors contend with every time a toilet is flushed which of course makes sense. Best of all for PVC is that it is much less expensive than crappy hoses.

I also used electrical PVC 90 degree sweeps for many corners to provide a gentle transition rather than typical elbows. The sweeps also offer greater strength than an normal elbow. And yes, many will say that electrical PVC sweeps should not be used but remember, we are fixing boats not covered by the plumbing code.

I found the marine head toilet odor us usually caused by the soup that forms on the salt water feed line to the toiletcwater inlet. You will see a blackish water firstxenter the bowl when flushed. Especially if unused for a long time. Be sure to give each toilets long flush when you first enter the boat. Also add a 2 inch pipe "T" manifold to the feed hose with a screw cap. Insert chlorine tablets. This will allow some chlorinated feed water to back drain into the feed line. These lines are especially problematic if they have a long level feed run. You can also buy biocide treated feed hose. Its expensive.

Also add a 2 inch pipe "T" manifold to the feed hose with a screw cap. Insert chlorine tablets. This will allow some chlorinated feed water to back drain into the feed line.

Very bad idea! Chlorine is highly corrosive and damaging to the rubber parts in toilet pumps...it also breaks down hose resistance to odor permeation.

These lines are especially problematic if they have a long level feed run.

They shouldn't have long runs. If the inlet thru-hull is a long way from the toilet, relocate or add a thru-hull that's close to the head.

One solution might be to plumb the head sink drain and toilet intake line to use the same thru-hull. (No reason why the sink can't drain below the waterline...it does on most sailboats). That would provide a means of flushing all the sea water out of the entire system--inlet line, pump, channel in the rim of the bow AND the toilet discharge line--with clean fresh water before the boat will sit. Just close the seacock and fill the sink with clean water...flush the toilet. Because the seacock is closed the toilet will pull the water out of the sink rinsing the sea water out of the whole system...without the need for any harmful chlorine.

Or...replace your toilet with one designed to use onboard pressurized fresh water. So-called "conversion" kits (everything but the bowl) are readily available and reasonably priced.

You can also buy biocide treated feed hose. Its expensive.

Not sure what hose you're referring to.... Trident 101/102 is a double walled sanitation hose has a biocide in the rubber formula, and very reasonably priced--$7-8/ft....but it's only available in 1" and 1.5" for use as toilet and tank discharge hoses...toilet inlet hoses are 3/4". I'm not aware of any biocide treated hoses that size.