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Old 10-14-2021, 05:36 PM   #1
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Holding tank slowly draining itself..

I got typical small to medium boat system with an 18 gallon tank, a Y-Valve and a Macerator and of course the sea cock ball- valve deep in the bilge.

With the Sea Cock open and the Y-valve in the “Normal” position, the tank is gravity draining from full to empty in 5-6 hours.

For some reason I thought this was not normal, but looking at the schematics, there is no check valves and the macerator will let fluid drain through the impeller.
(Everything is brand new: Head, tank, valves, etc. Not an issue of build-up and old seals)
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Old 10-14-2021, 06:34 PM   #2
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I got typical small to medium boat system with an 18 gallon tank, a Y-Valve and a Macerator and of course the sea cock ball- valve deep in the bilge.

With the Sea Cock open and the Y-valve in the “Normal” position, the tank is gravity draining from full to empty in 5-6 hours.

For some reason I thought this was not normal, but looking at the schematics, there is no check valves and the macerator will let fluid drain through the impeller.
(Everything is brand new: Head, tank, valves, etc. Not an issue of build-up and old seals)
Why would you leave the seacock and Y valve in the open position if you are not pumping the holding tank contents overboard? If you are within a no discharge area this alone would be illegal. Unless you are actively pumping the tank out they should be closed. Unless I am not understanding what you are saying….
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Old 10-14-2021, 07:28 PM   #3
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Why would you leave the seacock and Y valve in the open position if you are not pumping the holding tank contents overboard? If you are within a no discharge area this alone would be illegal. Unless you are actively pumping the tank out they should be closed. Unless I am not understanding what you are saying….
This is about plumbing, not legality.
In the past I pumped the tank when 3 miles off shore, or more.
Never noticed the tank draining by gravity before.
Guess I should go back to plumbing school if gravity draining is normal.
My bad.
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Old 10-14-2021, 08:11 PM   #4
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Yes they will do that. It will be a slow drain. If the tank is above the final outlet and there are no hose loops above the tank fluid level it will.
I would suggest that the only thing slowing the drainage is the macerator pump as the impellor seals the pump chamber, although not perfectly as you see.

It could also be telling you that the impellor needs to be replaced or cleaned if this is recent.

I set my holding tank to drain w/o a pump by just opening the seacock. When the boat was moving it was quite quick. Of course this was more than 35 yrs ago with my first boat.

I knew of another boat that was set up like than but they too kept the seacock shut.
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Old 10-14-2021, 08:23 PM   #5
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This is about plumbing, not legality.
In the past I pumped the tank when 3 miles off shore, or more.
Never noticed the tank draining by gravity before.
Guess I should go back to plumbing school if gravity draining is normal.
My bad.
But my point is that what you are doing isn’t legal so why would you even consider doing it?
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Old 10-14-2021, 08:50 PM   #6
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But my point is that what you are doing isn’t legal so why would you even consider doing it?
It is not legal to empty the tank within a no discharge zone for sure.
In the past I dump the tank my engaging the macerator pump.
Never seen the tank drain by itself.
Seemed weird, hence my question.
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Old 10-14-2021, 09:01 PM   #7
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. I would suggest that the only thing slowing the drainage is the macerator pump as the impellor seals the pump chamber, although not perfectly as you see.
I thought the impeller would stop the flow as well.
Guess not.
Called Raritan about it today, they said hell no.
(Previous macerator was Jabso, perhaps they are different..? )

Either way, thanks for the replies.
Guess I will change the valve positions now, but pain in the butt, lay down on your belly on deck, reach deep in the bilge and try to open/close the sea cock. More painful as I get older, hence I leave the valves open and just hit the switch when pumping the tank.
Until now as the tank is already empty, thanks to gravity.
(New sanitary system installed March/April this year, guess the plumbing changed although I told the contractor to just replace every piece and every part, not to re-design it)
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Old 10-14-2021, 09:09 PM   #8
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[QUOTE=LN-RTP;1045743]I got typical small to medium boat system with an 18 gallon tank, a Y-Valve and a Macerator and of course the sea cock ball- valve deep in the bilge. With the Sea Cock open and the Y-valve in the “Normal” position, the tank is gravity draining from full to empty in 5-6 hours.
[Quote]


I'm pretty sure I know what the problem is, but I need answers to a couple of questions to be 100% certain: Does the tank sit entirely above the waterline or is at least a portion of it below-waterline? Where is the discharge fitting located in the tank--ON the bottom of it? Or on a side or end? When the thru-hull is open, does water rise in the tank?


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Old 10-15-2021, 05:52 AM   #9
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"but pain in the butt, lay down on your belly on deck, reach deep in the bilge and try to open/close the sea cock."

An installed reach rod might be easy ti create.

An old style tapered plug seacock can easily be push pull cable operated.
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Old 10-15-2021, 07:10 AM   #10
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My overboard discharge came with an anti siphon valve after the pump and above the tank. This would eliminate your problem as far as the siphoning portion.

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Old 10-15-2021, 07:30 AM   #11
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. I'm pretty sure I know what the problem is, but I need answers to a couple of questions to be 100% certain: Does the tank sit entirely above the waterline or is at least part of it below-waterline? Where is the discharge fitting located in the tank--ON the bottom of it? Or on a side or end? When the thru-hull is open, does water rise in the tank?
Yes, the tank sits above the waterline and the discharge is at the bottom: The hose goes to the Y-valve, then to macerator then downhill to the bottom of the boat.

Quote:
. An installed reach rod might be easy ti create.
Yeah, it is coming. This boat is not made for retired guys like me..
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Old 10-15-2021, 07:31 AM   #12
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My overboard discharge came with an anti siphon valve after the pump and above the tank. This would eliminate your problem as far as the siphoning portion.

Ted
Sounds like, you have a vented loop?
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Old 10-15-2021, 08:00 AM   #13
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Sounds like, you have a vented loop?
Yes, I used to have a vented loop. I ended up removing the Y valve, pump, hose, vented loop and plugged the seacock. I'm a coastal cruiser with an 80 gallon holding tank. No need for overboard discharging.

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Old 10-15-2021, 08:22 AM   #14
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Yes, I used to have a vented loop. I ended up removing the Y valve, pump, hose, vented loop and plugged the seacock. I'm a coastal cruiser with an 80 gallon holding tank. No need for overboard discharging.

Ted
Yeah, been doing the same: Going to the pump out station after every cruise, then I installed a tank level sensor and realized the tank was draining itself. Guess I have been sucking up a lot of air at the pump-outs..
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Old 10-15-2021, 09:59 AM   #15
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The person who installed your tank and plumbing was totally clueless about how to design a gravity drain system. I suspect he used an off-the shelf tank that has pre-installed fittings and simply mounted it completely above waterline. There are two major problems with it:

The macerator pump is the first problem: There shouldn't be one in a system designed to drain via gravity...it's just a "roadblock." The only thing that belongs in the tank discharge line is a y-valve--one side going directly to the thru-hull --the other side going to the deck pumpout fitting.

The discharge fitting in a side wall AT the bottom of the tank is the 2nd problem. For gravity work as it should, the tank discharge fitting should be IN the bottom of the tank, not in a side wall AT the bottom of it because only tank contents above the top of a fitting in a side wall can drain. That will also allow sludge buildup in the bottom of the tank. This makes frequent rinsing out the tank very important!

The y-valve should only be open to the deck fitting and the thru-hull should remained closed while the boat is inside the "3 mile limit," opened to dump the tank only where legal to do so. Because the tank sits entirely above the boat's waterline, there's no need for a vented loop either.

Removing the macerator pump seems to be about the only "correction" that seems possible unless you want to replace the tank with one that has the discharge fitting IN the bottom of the tank. Just make sure to flood the tank with several inches of water after every pumpout or dump to flush the sludge out of the tank and the plumbing

The attached drawing shows the correct design for a gravity drain system.


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kanter's KISS holding tank.jpg  
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Old 10-15-2021, 10:14 AM   #16
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It does appear that the macerator was previously used to pump out through the thru hull via a looped vented circuit. so someone replumbed it.
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Old 10-15-2021, 10:19 AM   #17
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Thx Peggie.
Yes, the system is not perfect.
The Albins came from the factory plumbed like that.
The factory tank was rather small at 10 gallons so when I redid the whole sanitary system, using a contractor recommended by Raritan, we had a custom tank built @ 18 gallons.
Not sure the original system was designed for gravity only, all the sister ships I am aware of have similar systems with a macerator pump.
Yes, sludge will build up in the bottom, unless flushed rigorously, which I do at every pump out.

Yes, I will position the valve differently for inshore cruising and when inside the 3 mile limit.
Crossing the Gulfstream to the Bahamas however we leave the valves open.
It is nearly impossible to swap the tank with a bottom drain one, very cramped, the Albin 28TE is a pocket trawler type Weekender, lots of difficult access for engine service and other stuff including the plumbing.
Have learned to live with it however, 4 years now and I plan to keep the boat.
The old system was plumbed the same way, but don’t think the tank drained itself, perhaps the Jabsco macerator had a different pump with in impeller that blocked the ports..?
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Old 10-15-2021, 10:22 AM   #18
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. It does appear that the macerator was previously used to pump out through the thru hull via a looped vented circuit. so someone replumbed it.
Don’t think there was a vented loop onboard for the holding tank, but I did not take “Before and After” pics. Was just glad to get read of the old and smelly system with a small tank overflowing now and then.
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Old 10-15-2021, 12:11 PM   #19
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Thx Peggie.The old system was plumbed the same way, but don’t think the tank drained itself, perhaps the Jabsco macerator had a different pump with in impeller that blocked the ports..?

There are overboard discharge pumps that AREN'T macerator pumps (manual or electric diaphgram pumps), but all macerator pumps are impeller pumps. Liquids can seep slowly through them, not only outbound, but inbound too if the macerator pump is below the waterline.

From what you say here, I wonder if your tank was never intended to be a gravity drain system....that it was actually designed to dump the tank using the macerator pump. If your toilet is also above waterline, the builder may have designed the entire system to be above waterline, eliminating the need for vented loops in it. You just assumed that it's a gravity system because tank is entirely above waterline and tank contents are seeping overboard through the macerator pump.

If the macerator pump is below the bottom of the tank, that would explain everything--the side wall location of the discharge fitting, the "slow draining", AND that there IS a macerator pump in the system....and if it's doing more than just seeping slowly, I'd replace the impeller in it. I'm guessing--hoping, actually--that the pumpout line (line to the deck pumpout fitting) does not go through the macerator pump.


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Old 10-15-2021, 01:42 PM   #20
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So i had the exact reverse of this happening. Our boat has a holding tank and overboard discharge. After a while our holding tank started mysteriously filling up when we were not on the boat. Closed the sea cocks both intake and discharge. still filled up. found out the y valve was bad and seacocks are getting serviced at next haulout
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