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Old 07-01-2022, 19:38   #1
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Compost toilet installation through existing empty black tank?

Hi all, so I have searched the internet high and low but can't find any mention of potentially installing my new natures head toilet vent pipe directly to the old pump toilets waste inlet. The black tank has been pumped dry and is vented itself to the outside. So the question is...to save me having to replumb any pipework and to eliminate the need to install any new holes to the hull for venting; can I just hook up the fan vented natures head toilet to the old pump toilet waste inlet and allow the compost loo to be vented through the empty black tank which is itself vented? Is there a reason that I don't see this solution commonly used already? Am I missing something here?
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Old 07-01-2022, 20:24   #2
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Re: Compost toilet installation through existing empty black tank?

If I understand you correctly, I believe it would work. The only question is whether the existing tank vent is large enough to allow for the flow from the Nature's Head.

NH uses something like a 1" hose to vent the tank. Typical holding tank vents are more like 1/4". My sense is that this would be sufficient, given how little air is being moved, but I have no data to prove this.

Of course, removal of the existing holding tank is one of the benefits of using these heads. But I'm sure you have good reasons to go this route. I think what you propose would work, but it's impossible to know for certain.
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Old 07-01-2022, 21:25   #3
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Re: Compost toilet installation through existing empty black tank?

I agree with Mike - I'd like to see a bigger vent if possible but you'd probably be okay. Or were you thinking of converting the deck pompout to a vent? That might work better than the tiny holding tank vent.

Kind of a neat idea to simplify installation if you don't want to get rid of the blackwater tank for whatever reason. Can always change it up later.
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Old 07-01-2022, 21:52   #4
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Re: Compost toilet installation through existing empty black tank?

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Originally Posted by Junglebike View Post
I agree with Mike - I'd like to see a bigger vent if possible but you'd probably be okay. Or were you thinking of converting the deck pompout to a vent? That might work better than the tiny holding tank vent.

Kind of a neat idea to simplify installation if you don't want to get rid of the blackwater tank for whatever reason. Can always change it up later.
This is what I did, although I removed the holding tank. I then plumbed the old deck pumpout to the fan, and put a mushroom vent on it.
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Old 07-01-2022, 22:00   #5
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Re: Compost toilet installation through existing empty black tank?

You should check out the Boon Jon composting toilet from C Head.
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Old 07-01-2022, 22:05   #6
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Re: Compost toilet installation through existing empty black tank?

Sorry, posted to the wrong thread.
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Old 08-01-2022, 12:17   #7
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Re: Compost toilet installation through existing empty black tank?

I vent mine to a large cabin top cowling on my boat. I am on a tidal mooring and under sail the large cowling sucks air from the head… I don’t really need the little fan, though I would use it in the spring or fall if I had my boat in the water then.

I have had good results,though I was hesitant at first.
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Old 08-01-2022, 12:25   #8
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Re: Compost toilet installation through existing empty black tank?

Hi,

Interesting question and some good responses.

My two cents is that you may want considering plumbing your liquids tank to the holding tank, instead of dumping the liquids tank fairly often (depending on how much you use the head).

We live aboard our boat all summer at a mooring in a crowded harbor. Dumping the liquids tank overboard may or may not be illegal, but is, at the very least, rude to ones neighbors. Hence, we plumbed our Airhead liquids tank directly to our holding tank and vented the composter thru a small mushroom vent in the head. We like this arrangement for we only have to pump out the holding tank liquids every three weeks.

Just a thought. We're not the first composter owners who have done this.

Cheers, and enjoy the new composter. Once you get the hang of using it, you'll never want to go back to a conventional head with it's finicky plumbing.
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Old 08-01-2022, 12:29   #9
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Re: Compost toilet installation through existing empty black tank?

We installed our composting toilet using the vent from the old toilet as well. Just make sure you have an adequate size vent, and an anti siphon loop if heeling is an issue.

On another note, I'm amazed, 7 posts, and no idiot has come on and tried to convince you that a composting toilet is a bad idea! Or that it really isn't a "composting toilet"! Must be a record.
And FOR the record, we love our composting toilet!
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Old 08-01-2022, 12:46   #10
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Re: Compost toilet installation through existing empty black tank?

In order to get adequate air flow, a shorter hose of one inch diameter is ideal.
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Old 08-01-2022, 13:10   #11
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Re: Compost toilet installation through existing empty black tank?

My Nature's Head is vented via a deck-mounted mushroom vent. It is converted from the previous deck pumpout hatch that used to connect to my holding tank. This is one of the standard methods of venting a composting head (as other have mentioned).
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Old 08-01-2022, 15:57   #12
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Re: Compost toilet installation through existing empty black tank?

We occasionally get solid water and often spray over the old deck mounted holding tank pump out fitting, so that was a non-starter to use for the Nature’s Head vent. Instead, we use the holding tank vent outlet. Yes, it is much smaller: 19mm (3/4”) outer diameter, so about half of that for the inner diameter with fittings and connections.

After three years of use it seems to be fine, though we’ve had to replace the fan once as I assume it is working harder.

Another issue is the smell coming through the vent - it isn’t much, but it also isn’t nothing. It’s mostly a musty pee smell. As we are a catamaran, the vent outlet is under our bridgedeck, while the old waste pump out is on deck. It is definitely preferable to have the toilet vent out of the regular ventilation flows.
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Old 08-01-2022, 15:58   #13
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Re: Compost toilet installation through existing empty black tank?

Quote:
Originally Posted by Elzorro View Post
Hi all, so I have searched the internet high and low but can't find any mention of potentially installing my new natures head toilet vent pipe directly to the old pump toilets waste inlet. The black tank has been pumped dry and is vented itself to the outside. So the question is...to save me having to replumb any pipework and to eliminate the need to install any new holes to the hull for venting; can I just hook up the fan vented natures head toilet to the old pump toilet waste inlet and allow the compost loo to be vented through the empty black tank which is itself vented? Is there a reason that I don't see this solution commonly used already? Am I missing something here?

Don’t you want to remove the black tank? That is one of the benefits of a composting toilet - you can reclaim quite a bit of storage space.
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Old 16-01-2022, 16:09   #14
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Re: Compost toilet installation through existing empty black tank?

I agree withfxykty.

In fact, when we installed two full size C-Head Composting Heads with NO VENTILATION HOSES AT ALL with no “odor problems” at all. We use coconut coir.
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Old 16-01-2022, 18:46   #15
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Re: Compost toilet installation through existing empty black tank?

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Originally Posted by SIGMACHI View Post
I agree withfxykty.

In fact, when we installed two full size C-Head Composting Heads with NO VENTILATION HOSES AT ALL with no “odor problems” at all. We use coconut coir.
Which begs the question: is ventilation really a necessity in every climate or just under very humid conditions?
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