Smelly Grey Tank.
#1
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Hello,
My grey tank (waste galley and shower water) stinks. I have tried every chemical product including boat products, septic tank powder, vinegar, etc. I cleaned it out completely, but the smell came back.
It has been suggested that it is a result of having in adequate venting. This results in the water containing too many "bad" bacteria and not enough "good" ones, because the "good" ones require more oxygen than the "bad". Improving the venting will be a bit of a problem, so I do not want to waste my time unless it will work.
Does anybody have knowledge of this, please?
My grey tank (waste galley and shower water) stinks. I have tried every chemical product including boat products, septic tank powder, vinegar, etc. I cleaned it out completely, but the smell came back.
It has been suggested that it is a result of having in adequate venting. This results in the water containing too many "bad" bacteria and not enough "good" ones, because the "good" ones require more oxygen than the "bad". Improving the venting will be a bit of a problem, so I do not want to waste my time unless it will work.
Does anybody have knowledge of this, please?
#2
Senior Member

Plastic absorbs odors. Put some water and bleach in the tank and leave it there for a while, drain and do again. See what RV sites recommend for bleach strength. Don't leave bleach water in contact with your pumps' innards for long, if at all.
#3
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vodka usually works, not joking
#5

Igloo recommends vanilla extract for smelly ice chest and I can say for certain that it works! I use it in my storage bins on my boat when they start to stink and it works there too. A few big bottles from the dollar store should do the trick.
Vinegar may work, but I doubt bleach will do anything long term.
Vinegar may work, but I doubt bleach will do anything long term.
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#8
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Thanks guys for the advice. However I am sure the problem is in the water and I really want to check out the advice about lack of ventilation and oxygen in the tank. My current vent pipe is only 5/8 inch internal diameter, but it will be a hassle to change it, so I am asking if anybody knows about this good and bad bacteria question.
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#11
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Your coach doesn’t flush with salt water, everything in it dies off and rots. It’s a god awful stench.
I also vote for bad hoses. 🤙🏻
I also vote for bad hoses. 🤙🏻
#12
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5% Bleach solution.... fill it up to the top .... (20gal tank gets 1 gal bleach). Pour half the bleach in first, add the water, top off with the last half of the bleach. Let it sit overnight. Drain and flush. DO NOT use bleach with ANY other chemical.
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#13
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#14
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I figured waste meant the bowl, but you’re correct, it does say grey water........ Odd, Most sinks go overboard, and shower drains are generally into a sump and overboard. No need to tank grey water. If your shower drain and sink waste smell that bad, how is the fresh water tank? Do you have a sulfer smell from the spigots?
A shock with about a half gallon of bleach in 60 gals fresh water run into all lines and allowed to sit overnight fixed that for me. Multiple flush and fills to clear out residual bleach, and now I add a cap full every fill. Golden.
Now, if I would plumb my bowl with that water I’d be happier.
best of luck tracking it down
Ed
A shock with about a half gallon of bleach in 60 gals fresh water run into all lines and allowed to sit overnight fixed that for me. Multiple flush and fills to clear out residual bleach, and now I add a cap full every fill. Golden.
Now, if I would plumb my bowl with that water I’d be happier.
best of luck tracking it down
Ed
#15
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To answer the OPs original question, yes there is a difference between aerobic bacteria and anaerobic bacteria. The anaerobic bacteria grow in a low oxygen environment and stink, but aerobic bacteria - as used in many water treatment facilities - do not stink.
We bought the boat in my signature new in early 2002. GW puts a 10-gallon Groco tank in for waste, with an internal macerator. Like most of us, I used regular marine toilet chemicals to deal with odor. When the internal macerated died after about five years, I decided to make a significant change. I replaced the 10-gal Groco tand with a 15-gallon Groco Sweettank. Same internal macerator and external connections, but with the addition of an air manifold at the bottom of the tank, a connection on top for air supply, and a high-volume low-pressure air pump. Air was pumped into the tank 24/7/365 for the next 12 years (had to replace the air pump once), and no chemicals were ever added to the tank. The aerobic environment in the tank eliminated odor completely.
While keeping tank vent lines clear is always important, you will not have “good bacteria” unless you have forced air into the tank.
I have no financial interest in Groco, but that was one “Sweet Tank”.
We bought the boat in my signature new in early 2002. GW puts a 10-gallon Groco tank in for waste, with an internal macerator. Like most of us, I used regular marine toilet chemicals to deal with odor. When the internal macerated died after about five years, I decided to make a significant change. I replaced the 10-gal Groco tand with a 15-gallon Groco Sweettank. Same internal macerator and external connections, but with the addition of an air manifold at the bottom of the tank, a connection on top for air supply, and a high-volume low-pressure air pump. Air was pumped into the tank 24/7/365 for the next 12 years (had to replace the air pump once), and no chemicals were ever added to the tank. The aerobic environment in the tank eliminated odor completely.
While keeping tank vent lines clear is always important, you will not have “good bacteria” unless you have forced air into the tank.
I have no financial interest in Groco, but that was one “Sweet Tank”.
#16

if it smells like rotten eggs, it is probably sulfur bacteria, which can be eliminated with a chlorine and water solution.
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Many thanks for all your replies. ocnsir has answered my direct question and this is what I was getting at. It sounds as if a fish aquarium air pump could do the trick, be relatively easy to install and not require repeated chemical additions. I will give it a try.