Overboard discharge of holding tank.

markpierce said:

My macerator is between the toilet and the black[water tank. Is that unusual? Seems to be preferred. Best to have solids macerated before being sucked out for sewage treatment.

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I believe it's not uncommon to have one macerator between toilet and holding tank (especially for electric water-flush toilets) and then perhaps another/separate macerator between holding tank and overboard discharge thru-hull.

Yes, solids and paper and so forth in the holding tank has already been macerated once, and pump-out stations seem to appreciate that.



-Chris

WesK said:

It sucks it to the pump (vacuum). As long as the discharge is into space (the river, ocean, etc.) there is no significant pressure. Reduce the output of the pump down to 3/4 " and hook it to 25' of garden hose and you have pressure.

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??

Our overboard macerator won't pump-out underwater without some sort of outward-bound pressure. If the thru-hull is left open and the macerator is not running, the holding tank will fill up with raw/sea water (inward-bound pressure, at least until reaching the equilibrium point).

??

-Chris

ranger42c said:

??

Our overboard macerator won't pump-out underwater without some sort of outward-bound pressure. If the thru-hull is left open and the macerator is not running, the holding tank will fill up with raw/sea water (inward-bound pressure, at least until reaching the equilibrium point).

??

-Chris

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Mine is not like yours. Mine pumps out overboard above the waterline with no seacock. If your holding tank fills with seawater, I think there's a problem.

ranger42c said:

?? Our overboard macerator won't pump-out underwater without some sort of outward-bound pressure. If the thru-hull is left open and the macerator is not running, the holding tank will fill up with raw/sea water (inward-bound pressure, at least until reaching the equilibrium point). ??-Chris

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There's no problem...Chris just provided the perfect illustration of the reason why it's long been a "rule of thumb" that, unless the entire tank is above waterline and plumbed to drain via gravity, any below-waterline discharge thru-hull should always be kept closed except when actually dumping the tank. In fact, it's always been considered a good "rule of thumb" to keep ALL below waterline thru-hulls closed except when in use, but one that's largely ignored these days.

Wes, a macerator pump impeller simultaneously pulls AND pushes--IMPELS liquid through the pump (which is why it's called an impeller). A diaphragm pump--manual or electric also pulls and pushes liquid simultaneously. Electric toilets have two impellers---an intake impeller that simultaneously pulls in flush water and pushes it to the bowl and a discharge impeller that pull waste out of the bowl and pushes it down the toilet discharge line.

A separate macerator pump in a toilet discharge line is NOT that common, nor is it recommended....for a bunch of reasons: A macerator pump moves waste at about 12 gal a minute...toilets move bowl contents at varying rates. If they aren't moving bowl contents at the same rate--which is almost always the case if the toilet is a manual toilet, it can cause a backup or cause the macerator to run dry, which even if only for a few seconds at a time isn't good for the impeller. If the macerator should decide not to run at all, nothing will get past it.

There's really no need macerate waste going into the tank OR coming out of it. Solid waste is about 75% water and is broken up pretty well going through the pump, so they dissolve very quickly in the tank. "Quick dissolve" TP also dissolves just as quickly. In fact, both solids and TP dissolve quickly enough that an "overload" of either or both that causes a clog will dissolve on its own with an hour unless the clog was caused by someone who flushed something they shouldn't have...in which case, it would jam any extraneous macerator pump if it hadn't jammed the toilet first.

Peggie
http://www.amazon.com/New-Get-Rid-Boat-Odors/dp/1892399784/
"If you can't explain it to a six year old, you don't completely understand it yourself." --Albert Einstein

The "Clean Water Act" (Federal Water Pollution Act of 1977) mandated that boats must begin holding or treating toilet waste on Jan 1 1980. So in anticipation of this, the engineers at Jabsco immediately began brainstorming ways to empty a tank at sea...and came up with this one which, as the photo shows, was designed to be installed on the side deck... The larger opening was intended to be the pumpout fitting...the smaller one the discharge for the macerator pump. It quickly became evident that turning a macerator pump into a water cannon was NOT gonna work! Turning on the macerator if nobody had thought to make sure that side of the boat was the lee side in even the lightest breeze had predictable consequences...and there were a number of other blow up disasters. Apparently they also tried putting it in the side of a boat, 'cuz I saw one installed in the side of a Grand Banks (the current owner had no idea what it was), but that didn't work either. So it was back to the drawing board for the engineers at Jabsco....

Peggie
http://www.amazon.com/New-Get-Rid-Boat-Odors/dp/1892399784/
"If you can't explain it to a six year old, you don't completely understand it yourself." --Albert Einstein

catalinajack said:

Got one from Ferriollo. Drilled a hole in the top of my plastic tank, glued the threaded collar in place, cut the tube to lenght, screwed it in, calibrated to empty and full. Works like a charm. No fouling.

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Why was it necessary to use an internal sensor in a plastic tank instead of the external sender designed to go on the outside of any tank material except metal and wood backed fiberglass?

Peggie
http://www.amazon.com/New-Get-Rid-Boat-Odors/dp/1892399784/
"If you can't explain it to a six year old, you don't completely understand it yourself." --Albert Einstein

Giggitoni said:

I just checked our 1986 GB42 manual (as built). The above-waterline pumpout to an offshore facility, in addition to below-waterline and deck suction options, was added when the boat was being constructed in Singapore. So, Peggy, here is a first for you . It's possible that the original owner, who ordered the boat, requested and paid for this option.

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If so, I'd bet real money that either the original owne--or perhaps it was installed by a later owner--berthed the boat in a private dock at his home or somewhere where he had access to the sewer line.

Peggie
http://www.amazon.com/New-Get-Rid-Boat-Odors/dp/1892399784/
"If you can't explain it to a six year old, you don't completely understand it yourself." --Albert Einstein

HeadMistress said:

Why was it necessary to use an internal sensor in a plastic tank instead of the external sender designed to go on the outside of any tank material except metal and wood?

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When I had our holding tank replaced, I opted not to use a monitor such as a SeaLand Tank Watch which can become inoperable from sludge building up on the verticle slides. I opted for stick-on sensors (SeeLevel, Garnet Industries) before the tank was installed but, unfortunately, the monitor did not work reliably. With the tank being installed such that I do not have access to any of the sidewalls, I was forced to go to Plan B. I opted to use Ferriollo's sensor in a one-inch PVC tube. It works. I'm happy. Installation through the top of the tank was quite simple. I am not trashing the SeeLevel product. I think it didn't work because the tank installer taped the wire leads over the sensors which is specifically advised against and, since I no longer had access to the sidewalls, I could not fix the error.

Not to sidetrack the thread, but speaking of "discharge", this happened in Sept of this year:

"As a result, city officials said, over the course of roughly 10 days, the St. Petersburg authorities released 136 million to 151 million gallons of partly treated raw sewage..."

And that was just St. Pete...Tampa did the same thing. A quick google search will show that Long Island sound suffers the same fate, at least to some degree. A friend and long time boater in that area said that it's no secret...and anyone in the area can always tell it happens after every big storm. He said there was plenty of "visual evidence" to back up his claim, and his Admiral agreed.

At a holding tank size of 50gal, that's roughly the equivalent of 300,000 boats all discharging at the same time.

It's discouraging when individuals are so diligent in handling their waste, and can get heavily fined when they don't, to see government officials take actions which erase all of that effort over the course of a few weeks. And this was just one instance.

We now return to our normally scheduled programming.

"A quick google search will show that Long Island sound suffers the same fate, at least to some degree."


It used to happen quite often both on LI sound and near any larger NYC treatment plants. But now there is not often a problem due to some pretty extensive ($$) changes to treatment plants in both holding capacity and treatment techniques.
What many do not realize until they look is the affect that larger cruise ship destinations can have on this subject.

ranger42c said:

I believe it's not uncommon to have one macerator between toilet and holding tank (especially for electric water-flush toilets) and then perhaps another/separate macerator between holding tank and overboard discharge thru-hull.

Click to expand...

HeadMistress said:

Electric toilets have two impellers---an intake impeller that simultaneously pulls in flush water and pushes it to the bowl and a discharge impeller that pull waste out of the bowl and pushes it down the toilet discharge line.

A separate macerator pump in a toilet discharge line is NOT that common, nor is it recommended....

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Yep, I said "macerator" from the toilet but what I really meant was just the pump/motor assembly that functions as part of the toilet itself. Ours has a thing called a "chopper" in there, so I assume it functions much like a separate macerator would, at least briefly.

FWIW, ours is a pressurized fresh-water flush unit, so doesn't have an impeller to pull flush water in...

-Chris

I've always considered it to be the ultimate irony that on the very day Rhode Island's statewide "no discharge" law went into effect, a massive sewage treatment plant spill occurred in Providence that closed all the beaches and shellfish beds at that end of Narragansett Bay for a week.

Peggie
http://www.amazon.com/New-Get-Rid-Boat-Odors/dp/1892399784/
"If you can't explain it to a six year old, you don't completely understand it yourself." --Albert Einstein

With the storms in the Puget Sound region this weekend the news outlets have already warned the public about the coming raw sewage spills coming from the overloaded municipal sewage systems.

Yep, I said "macerator" from the toilet but what I really meant was just the pump/motor assembly that functions as part of the toilet itself. Ours has a thing called a "chopper" in there, so I assume it functions much like a separate macerator would, at least briefly.

That "chopper" doesn't function much like a macerator, it IS the macerator. Doesn't matter whether it's in a macerating electric toilet or a macerating overboard discharge pump, a macerator is just the "chopper"--essentially the same thing as the blade in a blender--nothing more.

So macerating toilets don't have a macerator between the toilet and the holding tank...the macerator blade--aka "chopper"--is a part IN the toilet pump.

What everyone calls a "macerator" (referring to an overboard discharge pump) is actually a "macerator pump"--a pump with a macerator blade in it. But everyone thinks that "macerator" is what the whole overboard discharge pump is called. So it's not surprising that you don't know what a macerator really is...I doubt if very many others here do either.

Peggie
http://www.amazon.com/New-Get-Rid-Boat-Odors/dp/1892399784/
"If you can't explain it to a six year old, you don't completely understand it yourself." --Albert Einstein

Our boat has two separate head systems. Each one has a macerating toilet, holding tank, and an overboard discharge diaphragm pump. Redundancy is great. Dhays, I think it's amazing that Seattle and Bellevue put up with raw sewage spills of thousands of gallons in Lake Washington and Puget Sound, but people freak out at the thought that a boater might dump a few gallons. I don't know anyone that would dump overboard. We have plenty of pumpouts available and also have Terry and Sons mobile pumpout service that will pump your tank for free in most areas.

dhays said:

Harshly put, but if our holding tanks get full with no legal discharge available it simply means we failed in our duty as a captain.

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Times have changed in the nine years since I have left US waters. However, I did run across situations where there was no legal discharge and not through my fault. Pump out stations that were advertised or in the guide books which could not handle a Krogen 42 or were not operating combined with weather that made it unsafe to venture out the inlet. This caused us to put in an Electroscan. Perhaps times have changed.

Although shockingly as it may seem there are no (or few) pump out stations in the Eastern Caribbean and most boats do not even have holding tanks.

Then there is a marina on the Tennessee River that also has an RV park and has warnings that you can't use any toilet chemicals with their new sewage system. Of course they also warn their travelift is out of service and that they're not taking any more long term RV's and waterfront sites have a 2 week maximum, they are currently working on their July 4 events, they aren't participating in the fall color cruise, but they do have paranormal tours.