Install Holding Tank in C&C 35 MkII

[Ghaegele]

I posted this over in C&C forum but figure I might have a better chance for info here:

I have recently taken over ownership of a C&C35 MkII. It does not have a holding tank and I need to install one. Has anybody done this job? Any advise on where to place tank and what tank to use would be greatly appreciated. Would like to get at least 15 gallon capacity.

I just purchased Peggy Hall's book (don't have it yet) and anticipate much help there. But still have many questions about where to put the tank.

Thanks, Greg

 

[Kevin3447]

I'll be going to a C&C 35 Mark I this weekend, and can take some pictures for you if you want. Let me know.

Kevin

 

[Ghaegele]

Yes!

Kevin, my understanding is that inside the C&C35 MkI and II are virtually the same so pictures would be fantastic! If the owner knows what size and where it came from that would be amazing too. Thank you!

And have a great sail. They are wonderful boats to sail, especially on the wind.

Greg

 

[Kevin3447]

Kevin, my understanding is that inside the C&C35 MkI and II are virtually the same so pictures would be fantastic! If the owner knows what size and where it came from that would be amazing too. Thank you!

And have a great sail. They are wonderful boats to sail, especially on the wind.

Greg

OK, I hope these pix help. The owner said that when he bought the boat, there was a bladder, but it leaked, so he replaced it with a 9 gal box. It's located outboard of the sink, in the head. You can see the lift-out cover in the upper-right of the first picture. The second picture is looking down that opening. The pumpout goes pretty much straight up to the deck - you should be able to see the hose in the third picture, behind the cabinet door. The picture needs to be rotated to the right, sorry about that. Let me know if you need more pictures, or have any other questions.

Kevin

 

[Ghaegele]

Kevin, thanks for the photos. The MkII has a slightly different head configuration. I could probably get a 9 gallon tank in there but I also want to have Y valves for through hull discharge and pump and need that space.

I printed out the Ronco catalog and went through all the different sizes and shape and settled on a working plan. Initially I wanted to keep my deep center v-berth locker for sail storage and use the port side v-berth locker for the tank, which also gave me a shorter run. But nothing would work easily in there as its an odd shape. Finally I started looking at tanks for the center v-berth locker and found the 13 gallon (B102). While it is slightly smaller than I was looking for it will do and will also give me about 18 inches of storage above the tank. The run to the head is about 4 feet. I will need a top discharge with the dip tube and top fill.

I should be able to vent it up to the hull near the deck through the chain locker. 1" tubing? Also, what is the recommended procedure for affixing the tank? I'm thinking of tabbing wood strips around the outline of the tank and then building a plywood box around it. I figure the tank should not sit on the hull but on wood strips. Should that be covered with a rubber? Here are a few pics of my layout. The larger locker is the center one.

 

[Ghaegele]

How to Install Tank?

I decided on a tank and built a mock up this weekend. (Apx. 21 inches long, it has a V bottom and tapers from 27" to 15" toward the bow.) It fits nicely in the space below the V-berth however, because the V of the tank and the slope of the hull are not identical, it rocks. Any suggestions on how to install the tank to support it and prevent movement? I was thinking of glassing strips onto the hull along the outline of the tank to support slats running below the tank. Also, is one 3/4 inch vent line running about 6 feet diagonally, to a through hull near the bow enough? Finally, any reason for an access port?

(The first photo is along the port side looking forward. The other is the starboard side, left is aft and right forward).

View attachment 31087

View attachment 31088

View attachment 31089

 

[Steve Dion]

Foam!

Your other option would be to glass stringers into the hull and then secure the tank with straps. I would suggest that you look for a larger tank if you can get it fit through the opening. 13 gal. is really not very much.

If you build a platform you can use any flat bottom tank that would fit through your opening.

 

[Ghaegele]

I know 13 gallons is at the low end of my needs, but there is very little storage and I need a place for my sails and equipment. I am off shore often enough when cruising that I can discharge overboard. (I'm installing a pump.)

Going through prior posts I see that expanding foam is recommended by some boat builders. Peggy doesn't like the idea as it conceals the tank and causes replacement problems. But I'm thinking of using it to support the bottom of the tank which is not in contact with the hull but for the center line. Glassing in stringers to attach straps is a good idea. I am also thinking of building a plywood box (removable for access) around the tank as I will be using the top for storage.

 

[Steve Dion]

You can use the foam that does expand very much. Lay down plywood on the foam before you put the tank on it. You will still need a way to strap the tank in place, so keep that in mind as you proceed.

If you do not want to use foam, you could also glass in plywood at the proper angle to accept the "v" bottom. You probably want to keep the area in the hull (V) clean so water/condensation would be able to easily drain into the bilge.

 

[Kevin3447]

Sorry I didn't see that you replied earlier. After reading Peggy's book, and dealing with my own boat (O'Day 28) this weekend trying to "Get Rid of Boat Odors", I have a couple of suggestions. I think I tracked down my odors to permeated hoses. One suggestion in the book was to make sure you pump enough water to push everything into the tank. I have 4' of 1.5" hose, so that's about 1 gallon per flush to make sure everything's in the tank. Unfortunately, I can't shorten my run, but maybe you can. Do you have room under the port settee instead of the v-berth? Even if it's less capacity in gallons, it might be more or equal in number of flushes.
Also, my tank has the discharge hose at the bottom on the side, which means when the tank is not empty, neither is the hose, which means it'll get permeated again. I think a top-mounted pumpout fitting would be better, but I don't have any personal experience with that and don't know the potential downfalls.

Anyway, just some things to consider, since I'm sure you don't want to do the job twice.

Good luck with the project,
Kevin

 

[Ghaegele]

Steve, thanks for reminding me that I need a channel for drainage to the bilge! (The build up of water from my chain locker would have had me searching for a leak in my new tank within a week!) The v in the bottom of the tank is flat bottomed, so I think I will lay about a 4 inch strip of plywood over the centerline leaving sufficient room for drainage. I can then fashion plywood supports for the sloping sides and do away with the troublesome foam. I'll screw and glue the frame together and secure it to the bulkheads! Problem solved.

As for the port side settee, the inboard locker has electrical equipment and, as one of only two easily accessible lockers in the main cabin is extremely important for storage. The outboard locker is very narrow and would have required major surgery to get a tank in there. I will use a dip tube so there should not be waste laying in the hose. By the way, my calculations give me a volume of about 1/3 gallon in 4 feet of 1.5 inch hose. Cutting that in half (not really possible) doesn't make a huge difference.

Any advice on the inspection port? Can't I add one if I ever need it?

 

[Gudenuph]

We doubled the effective volume of our holding tank by following this procedure. Evacuate the bowl, use a water filled plastic syrup bottle with the jet top (small orfice) to erase the skid marks with a forceful jet of water, evacuate the rinsings, clear any diluted evidence with one or two flush pumps. Also adopt the septic tank users mantra....If it's yellow, let it mellow. If it's brown, flush it down.
Happy sailing, Geohan

 

[Kevin3447]

Neither of the boats I sail on has an inspection port, and I'm not sure what you'd use it for. I don't see why you couldn't add one later if needed. You might want to add a level gauge, though, or at least a "Full" sensor with a warning light.

My mistake on the volume - it's been a while since geometry.

Kevin

 

[Ghaegele]

Geohan, I like the water sprayer idea! Kind of like the old ketchup squirt bottles? Good fun for my 8 year old son, too. And Kevin, a level indicator will be essential. Any recommendations? Simple and cheap.

 

[Bill1565]

Don't spend any money till you get the book!!!

1. All your connections should be to the top of the tank
2. You will need 6" clearance over the tank for fittings, elbows, hose clamps
3. Cover the raw plywood with cloth or lots of latex paint. It is harder than the Ronco plastic and can abrade the tank if there is vibration or movement between the two.
4. Consider enlarging the access hole into the space below the v berth.

Good Luck

 

[Ghaegele]

Thanks Bill. I now have the book which is very valuable in designing this system, though not so much directed toward installation of the tank. (My hope is that once installed by following Peggy's advice I will not need to consult it again!)

I did have to enlarge the access by a few inches to get this tank in. I figure I'll paint the lower plywood platform with epoxy resin and also place inner tube rubber between the tank bottom and plywood. Polyurethane paint to top plywood cover. And I have 15" of space above the tank. This was essential as storage goes at a premium in this boat.

I'm debating whether to use 3M 5200 adhesive to tack the support frame to the hull. It should prevent it from shifting against the fiberglass hull in rough seas. Thoughts?

 

[Peggie Hall HeadMistress]

Oh YucK!!

We doubled the effective volume of our holding tank by following this procedure. Evacuate the bowl, use a water filled plastic syrup bottle with the jet top (small orfice) to erase the skid marks with a forceful jet of water, evacuate the rinsings, clear any diluted evidence with one or two flush pumps. Also adopt the septic tank users mantra....If it's yellow, let it mellow. If it's brown, flush it down.
Happy sailing, Geohan

Doing it that way leaves waste sitting in the head discharge line to permeate it and also results in buildup in it.

The right way: Add a cupful or two of water from the sink to the bowl ahead of solids...then use the dry mode to flush ALL the way to the tank. Switch to wet mode for 2-3 pumps to bring in enough water to rinse the bowl and the head discharge hose...then switch back to dry to pump that water all the way through.

Except while in the slip or at anchor, I wouldn't recommend letting yellow mellow on a sailboat either...unless you want tacking to splash yellow all over the head! Flush it ALL the way through to the tank in the dry mode. Once or twice a day flush a couple of pumps of water through the system in the dry mode.

To pevent buildup in the hoses, last thing before the boat will sit, pour 1 cup of undiluted white vinegar into the bowl and flush that ALL the way through to the tank...do NOT leave it sitting in the bowl.