Saltwater in Holding Tank

Aug 24, 2019
5
Hunter 45DS Ala Wai Marina
I have a 2008 Hunter 45DS. The aft head has a valve to dump overboard or into the holding tank. The forward head doesn't appear to have a similar valve and when in leave the sanitation line open, salt water is being sucked into the holding tank. Any thoughts?
 
Feb 14, 2014
7,399
Hunter 430 Waveland, MS
Your forward hold tank dump valve is below the water line of your boat.
Jim...
 
Feb 14, 2014
7,399
Hunter 430 Waveland, MS
If your forward holding tank valve to sea is open, sea water will flow backwards until the sea and hold tank levels are equal.

Mine has a macerator pump on it, to overcome the back pressure of the sea level.
Jim...
 

RitSim

.
Jan 29, 2018
406
Beneteau 411 Branford
Could also be that the vent is blocked and the cooler night temps suck water in- depends on the amount.
Small amount - blocked vent
Larger amount - see above
 
Dec 2, 1997
8,708
- - LIttle Rock
I have a 2008 Hunter 45DS. The aft head has a valve to dump overboard or into the holding tank. The forward head doesn't appear to have a similar valve and when in leave the sanitation line open, salt water is being sucked into the holding tank. Any thoughts?
Not sure what you mean by "the sanitation line"...do you mean the line from the tank to the thru-hull, or the line from toilet to the thru-hull?
--Peggie
 
Aug 24, 2019
5
Hunter 45DS Ala Wai Marina
Not sure what you mean by "the sanitation line"...do you mean the line from the tank to the thru-hull, or the line from toilet to the thru-hull?
--Peggie
The Hunter manual shows a 1" line from the forward toilet to the holding tank. However there is a thru-hull valve between the toilet and the holding tank that says "waste discharge". When we open the thru-hull the holding tank fills with seawater. It seems like there should be a valve to direct the waste overboard or to the holding tank. There is a valve like that for the aft head.
 

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Feb 14, 2014
7,399
Hunter 430 Waveland, MS
I have a 2008 Hunter 45DS.
I downloaded that owners manual which is available to me from..
HunterOwners.com downloads

If you have the electric Quiet Flush toilets, then you have a single Hold tank and a single macerator pump.
All of your toilets flow to the single Hold Tank.

I saw an optional direct discharge at each toilet.
If I read the manual correctly, you should never have to use the Forward Cabin toilet in the direct Discharge mode.

If you want to use that optional discharge, you must close the through hull valve after each flush or...

It will back flow sea water to your main hold thank.;)
Jim...
 
Aug 24, 2019
5
Hunter 45DS Ala Wai Marina
I downloaded that owners manual which is available to me from..
HunterOwners.com downloads

If you have the electric Quiet Flush toilets, then you have a single Hold tank and a single macerator pump.
All of your toilets flow to the single Hold Tank.

I saw an optional direct discharge at each toilet.
If I read the manual correctly, you should never have to use the Forward Cabin toilet in the direct Discharge mode.

If you want to use that optional discharge, you must close the through hull valve after each flush or...

It will back flow sea water to your main hold thank.;)
Jim...
Thanks everyone. Jim I'm afraid you are right. I wonder if there is a backflow device I could install at the thru-hull?
 
Feb 14, 2014
7,399
Hunter 430 Waveland, MS
I wonder if there is a backflow device I could install at the thru-hull?
Yes, but a back flow device in human un-macerated waste is trouble in the making.
____
After looking at your Black Water system, it is a really nice set up, with fresh water flush.
Jim...

PS: The fact you see back flow proves that your Hold Tank vent is open and working well.;)
 
Feb 14, 2014
7,399
Hunter 430 Waveland, MS
One other comment on cleaning out your Hold Tank, when appropriate per law.

1) Empty your tank using the macerator. Shut down pump and close that thru hull
2) Go forward and open up that optional thru hull.
3) Fill your Hold Tank with sea water. Cleaning out the line from forward toilet to tank. Close that thru hull.
4) Repeat item 1)

We find that procedure cleans out our hold tanks of most everything.
Jim...
 
Dec 2, 1997
8,708
- - LIttle Rock
There should be a y-valve in the toilet discharge line--one side going to the thru-hull, the other side going to the tank...without one, flushes will try to go both directions. However, that line goes into the tank at top of it, so that's that's not how sea water is getting into tank. Apparently there's only a tee (common on Hunters) in the TANK discharge line with one side going to the deck pumpout fitting, the other side going directly to the thru-hull--apparently without even a macerator or manual diaphragm pump to dump the tank. I'm guesssing that both the tank and the toilet are teed into the same thru-hull, which is why flushing the toilet directly overboard fills up the tank with sea water. Nor does there seem to be a vented loop in either of the lines going to the thru-hull...required in all hoses connected to a below-waterline thru-hull. (There should also be a vented loop in the intake, but that's an issue for a different discussion).

If my guess about how your system is plumbed is correct, 2 tees need to be replaced with y-valves--the one in the TANK discharge line and the one in the toilet discharge line. The y-valve in the TANK discharge line needs to stay open to the deck pumpout fitting except while dumping the tank. The thru-hull really should stay closed except when dumping the tank too, but if you flush directly overboard most of the time (and your location indicates that you're not in US waters so that may not be illegal where you are), keeping that thru-hull closed all the time would be a problem UNLESS the secock is readily accessible in the head. In which case, vented loops installed high enough to be 6-8" above waterline AT MAX HEEL, not just when the boat's at rest, become even more important.

--Peggie