Slight Holding Tank Odor

[HHNTR111]

Last year, we installed all new stainless holding tanks, new hoses, valves fittings, and commodes, and we thoroughly cleaned all the adjacent spaces. The forward holding tank is under the V-berth, and the overboard pump is under my drawers and closet.

So, the question is, what do people suggest to eliminate the slight but persistent funky odor? I thought of one of those pine scented stick-on dispensers, but since I don't want my clothes, or me, smelling like a fake pine tree, I wonder what people have tried that works.

Thanks!

[forsailbyowner]

Odor from hoses? For keeping the vent odor down we've been using household ammonia. Its way cheaper than commercial deodorant and seems to do a better job. Were currently pumping out at a station, have to do some research to see how environmentally friendly it is before macerating it overboard.

[GordMay]

Thorough flushing at each use will ensure that the waste doesn’t sit in the hoses.
Copious ventilation of the holding tank eliminates most tank odours.

[HHNTR111]

Thanks, Gord. I think I now see the issue.

The overboard discharge pump for the forward holding tank is below the holding tank, whereas the pump for the aft tank is above that tank. So, when I discharge overboard (only in designateed areas...), waste stays in the forward pump, and not in the aft pump. So, until I relocate the forward pump, I'll flush overboard, run clean seawater through the commode, and then flush overboard again.

Thanks again for your thoughts.

[Watercolor]

Just a couple thoughts.

1. If you're in salt water try and flush with a goodly amount of fresh water as possible.

2. Any hose that is likely to have standing waste in it is a good candidate for smells. Do a simple clothrub on the hoses and smell test.

3. Do not use nylon fittings, especially when they have standing waste. Nylon absorbs a lot of moisture and can exude serious waste smells. That includes Marelon (Marelon is simply Dupont Zytel 13% glass filled nylon).

3. Because PVC is brittle it can develop hairline cracks and weep just enough waste to cause a persistent smell. At a minimum I'd use Schedule 80 PVC when possible.

[foggysail]

My take is schedule 40 PVC is tougher than you may think. I have used 1 1/2" PVC pipe for levering countless times in various temperature conditions. I put enough force on the pipe to bend it to a point where I expected failure. To date I have not broken a piece of schedule 40 without using a hammer.

OH-- my old sailboat along with my 40' Silverton waste lines are plumbed with schedule 40 PVC pipe.

[Hudson Force]

Most sewage smells are related to the activity of microbes. Decomposition by aerobic bacteria is far less offensive than the activity of anaerobic bacteria. This is why properly ventilated composting heads have no offensive odor. My holding tank had a hose barb that was available for a second vent and after adding this vent smells decreased. Take care and joy, Aythya crew

[foggysail]

Has anyone tried using a small air pump for airing the waste? West Marine mentions a system for this purpose in the current catalog.........which is on the boat, not here with me. I think the system is one offered by Sweet-Tank.

[delmarrey]

Originally Posted by HHNTR111

Thanks, Gord. I think I now see the issue.

I'll flush overboard, run clean seawater through the commode, and then flush overboard again.

Thanks again for your thoughts.

One thing that has to be remembered is saltwater is full of miniature life. Once it looses it's oxygen the life dies and the lil' creatures start to die, in turn starts to rot, which smells.

One should not leave anything in a holding tank for more then 72 hours. And then should always be flushed out with fresh water and a little bleach.

The aeration system works in the fact that it keeps the putrefying gases of the micro organisms from developing so easily. Like making wine. The sewage ponds here in Everett constantly have a fountain running.

[Watercolor]

As several cruisers have mentioned, good tank venting is critical. There are air pump systems available to inject air into the waste and keep the bacteria working. However, if your vents are working right, and it sounds like your's did at one time, you probably don't need the extra hassle, it's worth rechecking the vents and hoses.

Something about your message seemed to imply that the smell was minimal, elusive (your word was funky). Generally, a tank that is oxygen deprived is pretty much in your face, smell wise.

That's why I mentioned the hoses and nylon fittings (that includes Marelon). It's also very possible that, if you have PVC fittings, you should look for some leakage from a hairline crack. Or it could be a small leak on one of your new connections.

Regarding the use of PVC on boats. It's sad that the two main non-metal materials for marine plumbing fittings are PVC and nylon. Both are designed for stable applications like homes and underground use. Nylon and water are natural enemies, except for anchor rode where elasticity is important. Nylon will loose better than 50% of its strength within 24 hours of immersion in water.

Regarding PVC, there are many of well documented boat stories of PVC breaking with minimal effort and some at the worst of times. One such story involved a storm, a crew member, a fuel starved engine, falling on a PVC elbow attached to the waste tank output. Let me just say that the elbow broke completely, I'll leave the rest to your imagination. Read Bill Seiffert's book "Offshore Cruising" I believe is the title. He has a paragraph about a hairline cracked PVC elbow, a not so waterproof masthead junction box, and a non-functioning set of mast electronics (lights, radar, radios, etc.)

I have used PVC for years on my boats, I don't like it, but there aren't a lot of choices. Marine plumbing is the stepchild of the marine industry. That's why I recommend Schedule 80. It is stronger than Schedule 40.

[foggysail]

Watercolor---

There are no prefect solutions to anything, just solutions that are better than others. PVC can/will fail if stressed beyond its design limits. But by itself, PVC is one tough material. I doubt I personally will ever see a PVC pipe failure in my lifetime! Because it is ductile as are most plastics, it has durability beyond most boating needs.

Attached (I hope the site allows this) is a pointer that gives test data results on stressed PVC pipe. http://www.uni-bell.org/pubs/pvc_cyclic.pdf

Certainly, if one choses to go with schedule 80 instead of 40, he should find it much stronger. We were not there with those who claim to have experienced PVC pipe failures in boats. My presumption is there must be more to the story including severe mechanical stresses that most likely would have caused other materials to also fail.

Just my thoughts--

Foggy