Head tank fun.

[Jeffrey D]

Okay…Pulling the head tank today and having some ‘what were they thinking’ moments…

It looks like there are three vent lines. The two to the bow vent seem normal, but the one that sits next to the pumpout cap on deck has a tight-fitting cap. I’m assuming it’s there to provide ample intake during pumpout so as not to implode the tank. For the life of me, I can’t understand why there’s a line from the saltwater tap to the tank. Otherwise it has the regular in-at-the -top, out-at-the-bottom hoses. 

Switching over to the seacock area. 

The head hose leaves the head, runs through a vented loop, and then to the top of the tank. The discharge side of the tank all goes through the manual whale pump, either to the through-hull or the pumpout. 

My thought is to supply the head from the intake seacock. The head discharge will go directly to the tank. The tank discharge will go to a Y-valve, with one side going to the through-hull, and the other going to the pumpout. Along with the double vents to the bow, that would be it. 

Am I on the right track?  Looking forward to your thoughts!

[Jeffrey D]

Well……

Just going to toss out there that that was easily the most horrific thing I’ve ever had to do on a boat. 

That seawater-in fitting had some sort of filter on it:

But I can’t imagine what it was used for unless it was to flush the tank with saltwater during pumpout. Update: Chat GPT says it’s a flushing standpipe. 

The tank itself seems to be watertight, but I’m looking to replace it regardless, as I don’t need all the holes in it. I also don’t need - 1-1/2” inlet from the macerating head-just a 1”.

 It looks like this Ronco tank is the right one:

https://tank-superstore.com/12-gallon-marine-holding-tank-b105/

I figure I’ll keep the tank vents that go to the bow and abandon the vent next to the pumpout. It certainly doesn’t seem original. 

One other thing that struck me as odd-the head discharge line runs through a vented loop between the head and holding tank. I can’t say I’ve ever seen that on the discharge side, only the inlet. And this boat doesn’t have a loop on the saltwater side. 

[peter.c....@gmail.com]

I think the vented loop between the head and the holding tank is there because the different valves give you three options for the plumbing.  Head to holding tank is one, holding tank to overboard (through the whale pump), and finally head directly overboard.  In the head directly overboard configuration, you want the vented loop to prevent siphoning seawater back in through the pump-out valve.

[Guy Johnson]

"The tank discharge will go to a Y-valve, with one side going to the through-hull, and the other going to the pumpout."

From a plumbing standpoint you don't need a Y valve, a simple T fitting will work. You head goes directly to the tank, so there is no chance of overboard discharge while using the head. 

Guy 

Puffin 10M #6 (with a T fitting)

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From: pearso...@googlegroups.com <pearso...@googlegroups.com> on behalf of Jeffrey D <jeff....@gmail.com>
Sent: Sunday, December 14, 2025 7:23 PM
To: pearso...@googlegroups.com <pearso...@googlegroups.com>
Subject: [pearson] Re: Head tank fun.

 

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[Dan Pfeiffer]

I'll share what I did. I got a custom welded polypropylene tank from Triple-M Plastics.  It is quite large at about 30 gallons and shaped to fit the space.   It's only heavy if it's full.  If I am in a weight caring mode it is empty.  If I need the capacity it is there.  12 gal seems too small to me.  The tank has baffles in it. 

All fittings are on the top with dip tube for pumpout.    The head goes straight to the holding tank with no vented loop or overboard discharge.    The tank has two vents that lead to two vent-thru-hull fittings, one port and one starboard.  The inlet and both vents are on centerline.  There are three ports for flushing.  One all the way to port and one to starboard and one in the center.  They all have cutoff valves and there is a fitting to connect to a hose.   The flush inlets cover all three sections of the baffled tank.  They are plumbed with pvc.  There is a second dip tube that I can run to overboard discharge (with a pump) if desired someday.  Or it is a backup in case of failure for the first.  

Originally the inlet was at the edge to keep the hose run short.  But I released on starboard tack the hose could back-fill with heeling even with the tank mostly empty so I moved it to center.  It could still back-fill but the tank needs to be a lot more full for that to happen. 

Hope that all makes sense.  Sound more complex than it is? 

Some more photos here of the v-berth space and a test fit of a foam tank mock-up:
http://dan.pfeiffer.net/10m/v-berth_rebuild.htm


Dan Pfeiffer

On 2025-12-15 8:14 am, Guy Johnson wrote:

"The tank discharge will go to a Y-valve, with one side going to the through-hull, and the other going to the pumpout."

From a plumbing standpoint you don't need a Y valve, a simple T fitting will work. You head goes directly to the tank, so there is no chance of overboard discharge while using the head. 

 

Guy 

Puffin 10M #6 (with a T fitting)

 

Sent from Outlook

---

From: pearso...@googlegroups.com <pearso...@googlegroups.com> on behalf of Jeffrey D <jeff....@gmail.com>
Sent: Sunday, December 14, 2025 7:23 PM
To: pearso...@googlegroups.com <pearso...@googlegroups.com>
Subject: [pearson] Re: Head tank fun.

 

Well......

 

Just going to toss out there that that was easily the most horrific thing I've ever had to do on a boat. 

 

That seawater-in fitting had some sort of filter on it:

But I can't imagine what it was used for unless it was to flush the tank with saltwater during pumpout. Update: Chat GPT says it's a flushing standpipe. 

 

The tank itself seems to be watertight, but I'm looking to replace it regardless, as I don't need all the holes in it. I also don't need - 1-1/2" inlet from the macerating head-just a 1".

 

 

 It looks like this Ronco tank is the right one:

https://tank-superstore.com/12-gallon-marine-holding-tank-b105/

 

I figure I'll keep the tank vents that go to the bow and abandon the vent next to the pumpout. It certainly doesn't seem original. 

 

One other thing that struck me as odd-the head discharge line runs through a vented loop between the head and holding tank. I can't say I've ever seen that on the discharge side, only the inlet. And this boat doesn't have a loop on the saltwater side. 

 

On Sun, Dec 14, 2025 at 14:35 Jeffrey D <jeff....@gmail.com> wrote:

Okay...Pulling the head tank today and having some 'what were they thinking' moments...

 

 

It looks like there are three vent lines. The two to the bow vent seem normal, but the one that sits next to the pumpout cap on deck has a tight-fitting cap. I'm assuming it's there to provide ample intake during pumpout so as not to implode the tank. For the life of me, I can't understand why there's a line from the saltwater tap to the tank. Otherwise it has the regular in-at-the -top, out-at-the-bottom hoses. 

 

Switching over to the seacock area. 

[Dave Cole]

The fitting next to the pump out should be a rinse water input line, not a vent line.  That way you can put some water in while vacuuming out the tank to help get all the gunk out.

My toilet output line goes straight to the tank.  You've got a ridiculous number of valves, even if you wanted to pump over board.  Proper use of ball valves should be able to eliminate vented lines/loops, which are notorious for plugging up with waste.

My toilet/tank system has one valve.  The valve at the water intake thru hull.  

Best to keep it simple.  

Dave

10M #26

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[Jeffrey D]

I’m inclined to go super-simple. As Gary mentioned, there really isn’t even a need for a y-valve between the overboard/pumpout options, just a tee. I’ve always closed the head supply seacock unless the head is being flushed, and I can come up with a lockout for the overboard discharge to satisfy the Coasties. I’ve always been a pee-over-the-side guy anyway. 

I usually shoot hose water down the pumpout line, pump that out, and repeat. I guess that wouldn’t really rinse the tops and sides of the tank very well, but it’s a sealed tank and I figure the less penetrations and hoses, clamps, etc, the better. 

Has anyone else had good luck with the Raritan KO bacterial deodorizer? We started using it years ago on my son’s trawler and it does a great job. The only downside is that you can’t use any harsh chemicals (bleach based) for cleaning the head itself. Raritan has their CP product for the cleaning side. 

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