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Old 05-11-2019, 20:29   #1
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Blackwater discharge above the waterline?

Hi all,

A bit of a crappy subject but aside from aesthetic considerations, can anyone suggest a reason why you wouldn’t discharge blackwater from (fractionally) above the waterline?

It has occurred to me that this would remove one more potential point of failure from below the waterline.

Matt
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Old 05-11-2019, 20:52   #2
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Re: Blackwater discharge above the waterline?

My monohull used to do that before I converted over to a dry head. The only negative is it smells a bit.
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Old 05-11-2019, 21:16   #3
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Re: Blackwater discharge above the waterline?

Quote:
Originally Posted by GILow View Post
Hi all,

A bit of a crappy subject but aside from aesthetic considerations, can anyone suggest a reason why you wouldn’t discharge blackwater from (fractionally) above the waterline?

It has occurred to me that this would remove one more potential point of failure from below the waterline.

Matt
Tom Huckle used to have a half tonner called Outlaw with the toilet outlet on the transom.

The fleet used to have cruise events where boats cruised to a destination then anchored and socialized.

There does not need to be any reason other than aesthetic.
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Old 05-11-2019, 22:09   #4
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Re: Blackwater discharge above the waterline?

If the discharge is only fractionally above the waterline, would it lull
you into a false sense of security? A slight heel or additional supplies might put the discharge below the water line. I assume you will still include a stopcock?
I don’t think I would want a abovewater discharge because the solids will want to cake onto the exposed hull below the discharge causing foul odors. Further, the crappy piping leading to the discharge thruhull will continually vent its odor to your immediate surroundings.
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Old 05-11-2019, 23:56   #5
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Re: Blackwater discharge above the waterline?

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Tom Huckle used to have a half tonner called Outlaw with the toilet outlet on the transom.



The fleet used to have cruise events where boats cruised to a destination then anchored and socialized.



There does not need to be any reason other than aesthetic.


Ummm... I think I am missing something here. It looks like there was going to be some kind of observation regarding cruising and maybe anchoring? Was that going somewhere? Was there a problem with the placement of the outlet? (For instance, I could imagine people would be inclined to approach the stern with caution and maybe announce themselves early.)
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Old 05-11-2019, 23:58   #6
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Blackwater discharge above the waterline?

Quote:
Originally Posted by AndyEss View Post
If the discharge is only fractionally above the waterline, would it lull
you into a false sense of security? A slight heel or additional supplies might put the discharge below the water line. I assume you will still include a stopcock?
I don’t think I would want a abovewater discharge because the solids will want to cake onto the exposed hull below the discharge causing foul odors. Further, the crappy piping leading to the discharge thruhull will continually vent its odor to your immediate surroundings.


I can’t see any reason why piping to the through-hull would smell any different. But I can see how any buildup on the outside if the hull would be a problem.

And no, I would not be lulled into a false sense of security by such a setup. I treat all my through-hulls as though they are below the waterline because on a monohull they most likely will be at some stage.
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Old 06-11-2019, 00:00   #7
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Re: Blackwater discharge above the waterline?

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My monohull used to do that before I converted over to a dry head. The only negative is it smells a bit.


Thank you, good to know.
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Old 06-11-2019, 05:17   #8
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Re: Blackwater discharge above the waterline?

I have above the water discharge on my yacht, no issues. It is treated with chlorine in the holding tank so you do smell chlorine when discharging. As for any build up on the hull, not often but I do a visual check and spray with my water bottle if required. As for odour, never had any issues.
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Old 06-11-2019, 05:45   #9
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Re: Blackwater discharge above the waterline?

This discussion has gotten me to think about my set up. I have a holding tank above the waterline, then a discharge hose that goes to a macerator pump, then to a through hull below the waterline. The macerator pump has been frozen for some time (before I purchased the boat)but I have been using pump out facilities since I am on the Chesapeake. My thought/question is: can I eliminate the macerator pump altogether? I think the tank would drain down to the water level but I am sure there would be effluent left in the section of the hose below the water level. Will this eventually clog? Would this be better than a macerator pump that is prone to freezing? Of course, the through hull has a seacock, so I have control as to when the tank would drain.
Thoughts?
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Old 06-11-2019, 06:54   #10
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Re: Blackwater discharge above the waterline?

Quote:
Originally Posted by Tortuga's Lie View Post
This discussion has gotten me to think about my set up. I have a holding tank above the waterline, then a discharge hose that goes to a macerator pump, then to a through hull below the waterline. The macerator pump has been frozen for some time (before I purchased the boat)but I have been using pump out facilities since I am on the Chesapeake. My thought/question is: can I eliminate the macerator pump altogether? I think the tank would drain down to the water level but I am sure there would be effluent left in the section of the hose below the water level. Will this eventually clog? Would this be better than a macerator pump that is prone to freezing? Of course, the through hull has a seacock, so I have control as to when the tank would drain.
Thoughts?

It is much better for the sea to macerate the waste before discharge. This greatly accelerates dispersion and decomposition of the waste.


Even if your toilets are macerating electric ones, you will probably prefer to be pumping the waste through rather than leaving it to settle at the waterline. And if you don't have macerating toilets, then you are asking for a clog to leave unmacerated waste standing in the lines like that.


Macerator pump should not be "prone to freezing". They are very reliable if good quality and installed right. Don't run them dry.
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Old 06-11-2019, 09:34   #11
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Re: Blackwater discharge above the waterline?

On my FP Belize 43 the discharge for one head is just below the waterline. For the other it is 2ft above the waterline between the hulls. The previous owner added a 6 inch stub to the outlet to help keep the discharge away from the hull.
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Old 06-11-2019, 09:37   #12
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Re: Blackwater discharge above the waterline?

Aesthetics are the only argument against a tank discharge thru-hull above the waterline...There are even a few builders who've put it there. The worst downsides are, the discharge can stink...waste can stain the gelcoat below the thru-hull if not cleaned regularly...and you definitely want that side of the boat to be on the lee side of any breeze when dumping the tank. Discharge directly from the toilet above the waterline is another matter that can make you very unwelcome in an anchorage.


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Old 06-11-2019, 09:45   #13
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Re: Blackwater discharge above the waterline?

I built a boat once with an outlet a couple of inches above the waterline - for the very reason you suggested. I wouldn't do it again, because it made a really annoying 'click, click, click...' when wavelets ran past it on the outside of the hull and covered/uncovered it when we were moored or anchored.
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Old 06-11-2019, 09:46   #14
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Re: Blackwater discharge above the waterline?

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Originally Posted by GILow View Post
I can’t see any reason why piping to the through-hull would smell any different. But I can see how any buildup on the outside if the hull would be a problem.

And no, I would not be lulled into a false sense of security by such a setup. I treat all my through-hulls as though they are below the waterline because on a monohull they most likely will be at some stage.
Smell will not travel back up through the water , therefore your smelly waste will not stink under water but if out let above water line the smell will escape through the air UPWARDS and in the breeze , at least you will know someone is on the toilet
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Old 06-11-2019, 09:51   #15
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Re: Blackwater discharge above the waterline?

Why is there a concern at all?

The probability of proper seacocks, properly installed, failing is exceedingly low. Seacocks should be "normally closed", i.e. only opened for the brief periods that they are functionally required to be open. If that is SOP in your boat, you obviously inspect the seacocks and their hose connections as you open and close them. If the inspection shows that a seacock is suspect, you repair it chop chop, don't you :-)?

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