Holding tank breather - fit an air pump?

2

2copplane

Well-Known Member
Joined
28 Aug 2009
Messages
223
Location
Fleetwood
Visit site
Lots of posts on here regarding sizing of holding tank breathers the theory being it needs to be large enough to allow fresh air and maintain aerobic microbes as the anaerobic make the nasty pong.

I'm fitting a tank toward the middle of the boat and planning to fit a small breather of about 18mm and 4 metres long.

I'm sure this will be fine for gravity emptying the tank but I'm certain it isn't enough to maintain aerobic microbes and it wil quickly become smelly.

If it does cause a stink I'm thinking of a plan b to fit a very small air pump of about 4 watts to push fresh air in to the brown soup they are a couple of quid so I can carry spares.

I expect it is a terrible idea but interested in opinions.
 
The breather also allows air out, both as the tank fills and also to let gas out, so an air pump is unsuitable.

The standard TekTanks recommendation is the normal 38mm hose connected to a charcoal filter and then to a clam-shell type hull fitting. If you can't manage that then an open pipe is probably the best you can do. Be prepared for some whiffiness.
 
We regularly overfill our holding tank and hear the trickle of the "liquor" spilling over into the sea. It's then time to use the other toilet or get out to sea or use the marina toilets.

Unless you had some clever valve/bypass system I reckon that the "liquor" would quickly destroy any pump other than a purpose-built effluent pump. :ambivalence:

Richard
 
Graham_Wright said:
I think that's a great idea. Blow air in but you also need an outlet.
Click to expand...

Surely the outlet would be the normal tank vent ..... but I think the problem would then be that continuously blowing in fresh air would create a permanent smell around the vent outlet unless you had some system of blowing in fresh air intermittently or very very slowly, like a trickle sort of rate.

Richard
 
Last edited:
RichardS said:
Surely the outlet would be the normal tank vent ..... but I think the problem would then be that continuously blowing in fresh air would create a permanent small around the vent outlet unless you had some system of blowing in fresh air intermittently or very very slowly, like a trickle sort of rate.

Richard
Click to expand...

It shouldn't, this is a variation on the Peggy? wotsername idea of keeping fresh air above the liquor. The premise being that it's anaerobic digestion that smells, keep it aerobic and problem solved. It's something I've thought about too but with 100l tank it only gets whiffy after about 4 days

Btw she decries the charcoal filter as it further restricts airflow
 
I don't think everyone understood the OP:
* The air pump is blowing air to the bottom of the waste. It is only pumping clean air and is thus not affected by the waste.
* Because the waste becomes aerobic, there will be very little odor. I have tested this for Practical Sailor and there are commercial systems. It does work, through it is more complicated than some would like. The flow is slow slow that there is no detectable odor.
* A clam shell is bad idea because it makes it difficult to backflush the vent with a hose. A plain mushroom is best.
* Carbon filters have some downsides too. Most importantly, if they get wet (seawater or waste) they plug, so they must be located very smartly. They can also increase the risk of permiation, since the smell in the tank will be even worse... though with a 3-4 meter hose, probably not.
 
I was advised to have 38mm breather pipe and thru hull fitting so that when it is rapidly sucked out through the deck fitting there is no risk of the tank imploding - as you might get with a very narrow breather pipe and/or thru hull.
Paul
 
Pavalijo said:
I was advised to have 38mm breather pipe and thru hull fitting so that when it is rapidly sucked out through the deck fitting there is no risk of the tank imploding - as you might get with a very narrow breather pipe and/or thru hull.
Paul
Click to expand...

I should have stated in the original post that I'm not fitting a pump out capability. The tank is only 25l and for simplicity will be gravity emptied. So it really just a question of keeping it smelling sweet.
 
I think there is a lot of merit in this idea. Many motorhomes, including ours, have device called a SOG (sucks out gases) that is small fan swiched on when the chemical toilet gate is opened. It draws air out from above the contents and blows it outside the van. Using this it is possible not to use any chemicals at all as the smell never enters the van.

As suggested I think you would need an entry snd exit hose to ensure circulation. However I must say that our 50 litre holding tank with only a 1 inch vent does not seem to smell excessively.
 
I think there is a lot of merit in this idea. Many motorhomes, including ours, have device called a SOG (sucks out gases) that is small fan swiched on when the chemical toilet gate is opened. It draws air out from above the contents and blows it outside the van. Using this it is possible not to use any chemicals at all as the smell never enters the van.

As suggested I think you would need an entry snd exit hose to ensure circulation. However I must say that our 50 litre holding tank with only a 1 inch vent does not seem to smell excessively.
 
2copplane said:
Lots of posts on here regarding sizing of holding tank breathers the theory being it needs to be large enough to allow fresh air and maintain aerobic microbes as the anaerobic make the nasty pong.

I'm fitting a tank toward the middle of the boat and planning to fit a small breather of about 18mm and 4 metres long.

I'm sure this will be fine for gravity emptying the tank but I'm certain it isn't enough to maintain aerobic microbes and it wil quickly become smelly.

If it does cause a stink I'm thinking of a plan b to fit a very small air pump of about 4 watts to push fresh air in to the brown soup they are a couple of quid so I can carry spares.

I expect it is a terrible idea but interested in opinions.
Click to expand...

Here's a discussion on the cruising forum including comments from Preggie Hall

http://www.cruisersforum.com/forums/f115/aeration-pumps-for-holding-tanks-155110.html

This is a product Preggie refers too

https://www.groco.net/products/marine-sanitation/sweet-tank-odor-prevention

I did consider adding a small aquarium air pump to do something similar but never got round to test it out.

here's another similar product

https://www.amazon.com/B15-Marine-Metal-aeration-Bubbles/dp/B000EYWNVQ
 
Last edited by a moderator:
I don't like the sound of "excessively".
vyv_cox said:
I think there is a lot of merit in this idea. Many motorhomes, including ours, have device called a SOG (sucks out gases) that is small fan swiched on when the chemical toilet gate is opened. It draws air out from above the contents and blows it outside the van. Using this it is possible not to use any chemicals at all as the smell never enters the van.

As suggested I think you would need an entry snd exit hose to ensure circulation. However I must say that our 50 litre holding tank with only a 1 inch vent does not seem to smell excessively.
Click to expand...
 
vyv_cox said:
:) Does not smell at all inside the boat. I have noticed a whiff on the odd occasion when the toilet has been used and I have been standing on an adjacent pontoon. The smell was of fresh sewage rather than H2S suggesting that there was plenty of air contact., no anaerobic bacteria.
Click to expand...

how long is your 1" breather pipe?
 
You must log in or register to reply here.

Other threads that may be of interest

lustyd
Fuel Gauge Calibration
2 3
Replies
45
Views
726
paulbrown22
P

Share this page

Top