Coverting MK11 aft water tank to holding?

[cmainprize]

We are freshwater sailors and have not filled up the aft water tank for several years.  We have plumbed every fixture in the boat to lake water ( including hot water) except for a small tap in the the head and galley for brushing teeth and making coffee and cooking.  We use lake water for everything else.  We usually end up dumping the the bow tank before it's empty because we end up at a marina anyway for a pumpout.  

We need to get a pumpout every 7 days or so.  Two adults, two kids.  We could do all kinds of stuff to reduce our need for a bigger holding tank but we don't want to.  I think the aft water tank is 42 gallons and will be perfect.

So what I want to do is remove the port side holding tank and re plumb the waste line to the aft water tank.  If I can modify the tank that is there great, if I need to change the tank that's fine too.  The wast line will be a little longer and the tank is higher than the head.  I don't trust the joker valve to hold back 400 pounds of poo so I will put a shut off on the line when the head is not in use.  

any thoughts?

[Mike and Joanne Stimmler]

Cory,
Wow, to me that seems like a lot of pumping to get that poo all the back to where the aft water tank is.
The only idea I can come up with is to keep the original holding tank (close to the head)and connect a maserator pump to it's normal fitting on that tank and run that hose back to the water tank you're trying to use. I'm not sure though if the existing water tank would be usable because it's designed for water, not waste, and it's also not plumbed to be able to be pumped out, so I would think that you would wind up replacing the existing water tank with one designed for waste. One good point is that you would increase your holding tank capacity tremendously.
One bad point is, the resale value could suffer if the buyer doesn't agre with your logic.

Peggy Hall will probably chime in on this and what ever she says is exactly what I meant in the above paragraph 

My thoughts exactly!

[Joe Kern]

LOL - I was going to suggest that whatvere Peggy says is what I would do.

I have zero interest in ever doing what you are suggesting but I am very much looking forward to the discussion by Peggy, Stu, Ron and some of the other experts.   This will be some fun reading.

Joe

[Ron Hill]

Cory : I'm not too sure about the discharge rules in your area, but I'd go for a USCG Type I MSD head.  The USCG certifies the Type I as dischargable.  There are a few out there and the Electro Scan is one of the popular names.

A Type I MSD most certainly would be much easier and cheaper than trying to re-plumb $$ to a specially made rear holding tank $$$$.   A thought

[cmainprize]

Thanks for the reply's.  I too am looking forward to to see what the experts have to say. 

I measured the distance today, the waste line run lenth increases by 4.5 feet.  I think the bigger issue is that the top of the tank is about 2 feet higher than the head.

A new tank, hoses and fittings is around 500-600 dollars.  I could care less how much it costs if I get a 40 gallon holding tank and it all works perfect.    The toilet says it can pump up to six feet of head.  In addition I will be able to reclaim a big locker for more wine, spare parts and move the tank out of the living area.

Pumping overboard is not an option in the great lakes.  At least I don't think so.

[Peggie Hall]

LOL - I was going to suggest that whatvere Peggy says is what I would do.

It's  a horrible idea! Not converting an unused water tank to waste holding...that's done all the time. But A) using lake water for everything but cooking and teeth brushing (please don't tell me you use the water in your marina for ANYthing except toilet flushing!)...and B) 42 gallons of sewage holding turns a 34' sailboat into a honey barge!

About the lake water...you cry in response, "But we don't drink it, we only bathe in it!"  You "drink" more of it than you think you do...you wash your hands in it, then pick up a sandwich...wash dishes in it, but don't sterlize 'em (only germophobics would!)...rinse out a cup in it before filling the cup with coffee made with your "pure" bottled water...when you shower, it gets into your nose, eyes, mouth.  Prob'ly ok out in deep water in the middle of the lake (unless a fish or a duck or a goose next your boat has pooped just before you run water)...but NEVER ok in the marina...the water in EVERY marina is filthy, mostly due to runoff, but oil in bilge pump discharge, people flushing directly overboard, whatever gets washed off boats...and then there's wildlife poop being washed into the water in those wonderful secluded anchorages.

Doncha just love it when some ol' bag comes along and rains on your parade?

Your family of four can make your existing tank last a whole week??  That's 12 gallons/day for most people...so if you're living aboard and being aboard full time, that's incredible!  Most people would need at least an 80 gallon to do that!

So my advice:  count your blessings, and replumb your boat to draw from your water tanks filled with purified "city" water again...and look forward to the days when the two kids will be old enough to leave home and drop the demand on your holding tank by 50%.

[Roc]

Cory,
In the mkII, forward of the holding tank, is a storage area accessed by lifting the port side cushion.  I bet you can set a smaller sattelite tank in that area and fit it together with the main holding tank to give you extra capacity.  Peggie might be able to advise as to how to couple two tanks together (hose bridge or something)

[Jim Hardesty]

Cory,
The small holding tank would rate as my #1 dislike about the boat.  We sail Lake Erie, ie no discharge.  With just the two of us pump outs are every 3 to 4 days when staying aboard.  Believe me, you don't want to sail hard in our big choppy waves with 3/4 full holding tank.  But due to lack of good anchorages we stay a lot at yacht clubs or marinas where pumpouts are free or low cost ($5).  So I'm living with it.
Back to fixes, what I've thought about is removing the marcerator(I've done that) and getting or making a new holding tank utilizing the entire space.  Less of course battery switches.  My guess is that would add 10 gal. or more.  You may be able to remove the partition forward (check with Catalina before doing that) and make or buy an even larger tank. 
Let us know what you do.  With more and more no discharge zones more owners are going to find that the holding tanks are just too small.
Jim

[Wayne]

What about the space under the cockpit seat  that you can see from under the head sink?  Totally unused space . . . could you add another thank there?  It is located uphill from the existing holding tank . . .

[Peggie Hall]

Peggie might be able to advise as to how to couple two tanks together (hose bridge or something)

I'm not a fan of linking two tanks together, 'cuz they have to be linked at the bottom and the link should be 3" (at least 2").  Both tanks have to be vented...both have to be maintained...and together they don't hold anywhere near as much as a single tank as big as the space they both occupy.  It's just not a good solution if there's ANY other way.

Learning to use a lot less flush water can increase the number of flushes a tank can hold by as much as 50%. Most people only use the "dry" mode to remove the last bit of water from the bowl...unaware that any toilet that's working anywhere NEAR factory spec can move bowl contents up to 6 linear feet and/or 4 vertical feet in the dry mode. So on most boats, you really only need to use the wet mode to rinse the hose behind the flush.  

If it's uphill all the way to the tank and/or the tank is too far from the toilet (more than about 6' is too far), modifying the plumbing to put a loop in the discharge line immediately after the toilet, so that the toilet only has to push bowl contents and rinse water over the top of it...gravity will do the rest...can solve the problem.  Some plumbing mods can also solve the problem you have sailing in choppy waters with a 3/4 full tank too.

Actually, the number of ND zones is not increasing. A lot of talk in some areas, but that's all.  Except for some marinas who think they're "doing the right thing" but apparently haven't figured out that a) the discharge from a Type I or II is cleaner than the water in any marina and b) no more than about 5% boats will ever have a treatment device.  Marinas are private property...they can make their own rules. But there hasn't been a new NDZ added to  EPA list in at least 5 years.

[cmainprize]

Thank you again for all the responses

The choice to use lake water for washing dishes, hands and showering was an easy one for us. In our area, thousand of boaters and hundreds of thousands of cottagers use lake water for everything (except drinking) in their boat and cottages. Marina's are definitely not as clean as the mainbody of the lake(s) but I have never been in a marina in Georgian bay, lake Huron, or the north channel I would not swim in.  I will not be changing my plumbing back anytime soon.

As for having to much holding tank on board, I can't believe any boater could say that with a straight face.  

Everyone uses their boat differently and has requires a setup geared for their intended use.  We avoid marina's at all costs and don't like making our travel plans around pumpouts.  

I have considered having a new tank made to make better use of the existing space, but my math only gets me an additional 5-6 gallons.  I could use the forward settee locker for a second tank as well but I just hate cutting holes, especially big ones in the boat and I would be losing storage.  The choice to use the aft water tank seemed logical to me because it is wasted space for us.  I plan to remove the tankand have new hose bosses installed for waste intake and discharge.  I will run the waste line as high as I can go from the toilet then it should be all down hill to the tank from there.  I will use the aft water tank deck fill location for the pumpout fitting.

[Dave Spencer]

Cory,
It seems the discussion is split two ways... salt water folks seem to question the merit of your idea but freshwater sailors (like me) see the value in increasing holding tank size at the expense of fresh water capacity. It stands to reason that time away from port in salt water is limited by fresh water capacity and fresh water sailors are limited by holding tank capacity.  Like you, we use lake water for most cleaning tasks and only use our fresh water tank for coffee, brushing teeth, etc.  Even then, we often freeze bottled water to keep the fridge cold and then drink the melt water to avoid "tank taste".  
We have a Mk1.5 with the holding tank under the port settee and one fresh water tank under the stbd settee (plus the huge aft fresh water tank).  I'm not thinking of increasing our holding tank capacity since there are only two of us and holding capacity seems adequate.  But, there is far more fresh water capacity than we could every use.  Your post got me thinking about pulling out the stbd fresh water tank and gaining all that useful midship stowage.  I could keep the tank at home and reinstall it if we ever want to sell the boat.  (which seems unlikely since we just bought it last year)  As Ron says... a thought... but one I likely won't act on in the near future.

[Ken Juul]

If you haven't all ready done so....the Raritan PH series is supposed to require a lot less flushing water than the factory installed Groco/Jabsco head.  Changing the head might be a first step.