THE CONCEPT

Having experience with a 13 gal. tank on our previous Pearson 30 we had two key requirements for our new Northstar's tank:

1. Minimize odors. 2. Maximize tank size.

A key decision on requirement #1 was to keep the tank in the bathroom, which has a 4" deck Dorade ventilator. By facing this ventilator aft any head odors are pulled out of the boat's interior. (Our boats are always moored, not in a slip, so the wind is almost always from forward, and in our harbor there is almost always wind. It also seems that the time that the boat sits closed up and idle in the sun is the worst time for odor control. ) This choice also keeps all the odor control problems associated with the head in one area, and doesn't allow the tank to encroach on valuable dry storage space elsewhere. In addition we chose a tank with the thickest possible wall to minimize odor penetration.

We considered locating it in the lower outboard locker in the bathroom, behind the toilet and against the portside of the hull. That required a more expensive custom tank, blocked some key access to water fill, vent and waste hoses and the side of the hull, and had no more capacity than our final choice. We choose instead to sacrifice the storage space in the vanity outboard (to port) of the wash basin which was relatively useless to us anyhow. In addition there is unused space inside the inverted U molded fiberglass section in the vanity. By cutting some of that away we could fit a larger tank. It meant some major surgery to the vanity and bathroom structure but was well within our average carpentry abilities.

Careful measurements showed that the space would fit a rectangular tank 24" high, 18" wide and 12" deep, about 20 gallons, which we deemed adequate. A tank possibly 2" taller could have been accommodated by bringing the tank closer down to the toilet floor level, but it would have blocked essential hose passages beneath it from the outboard locker, and unduly weakened the floor in the bathroom by removing the vertical stiffener section in that area. As it is the tank is entirely contained within the vanity which is 26" high and about 2" off the toilet floor level.

THE TANK

A search of several tank vendors turned up a stock tank at Ocean Link, Inc. in Rhode Island almost exactly this size. We ordered their OLT-400 tank, 17" X 24-1/4" X 12", 20 gallons, for $254. Another benefit of this choice was that their tanks are very thick, close to 3/8", for strength, abrasion resistance, and odor control. Buy this tank with a 1-1/2" inlet at the top corner of one 12" x 17" face and an 3/4" vent outlet at the opposite corner of that face. In the middle of that face, between the other two fittings locate a 1-1/2" dip tube outlet to be plumbed to the deck waste fitting. At the upper aft corner of the opposite face (which will be the inboard face, inside the vanity, once the tank is in place) purchase another dip-tip outlet which will allow pumping out the tank from inside the boat. These fittings added approximately $100 to the cost of the raw tank and must be installed by the manufacturer. I added a Beckson 4" access port to the top of the tank mainly to allow inserting a new sulfation-type odor control rod, but also to allow easily cleaning and deodorizing the tank if/when necessary. The Beckson ports seem to have the best sealing mechanism of any -- a double seal, including an O-ring.

NOTE: Ocean Link advocates, and my experience supports, drawing from the tank with fittings located at the top rather than the bottom. These fittings include internal tubes reaching to the bottom of the tank to allow suctioning out the contents. Sooner or later any plumbing fitting will leak. One located at the top will not leak a full tankful of sewage into your bilge. (The leak will always be worse when the tank is full!) What Ocean Link calls their dip-tub fitting also allows pumping out closer to the bottom of the tank than does a 1-1/2" outlet near the bottom. (The latter sucks air instead of waste as soon as the level drops below the upper edge of the fitting.) The one advantage of locating the internal outlet at the bottom is that things could be arranged to empty the tank directly thru a nearby thru-hull by gravity, without benefit of a pump. I preferred the complication of a pump to waking up some morning with a bilge full of sewage, most likely when conditions are rough!

CUTTING AWAY AND REMOVING STUFF

1. Temporarily remove the toilet (3 lag screws holding it to the floor and two hoses), the vanity door, and the lower outboard locker flap (over the toilet.)

2. Cut the outboard vanity section away at exactly 17" in from the outboard wall (i.e. the one behind the toilet.) Use fine blades and straight cuts so that the vanity section can be reused and fitted back in place at the end.

3. Remove screws inside the loose vanity section on cleats holding it to the bulkheads etc. to completely remove it. This will leave several 3/4" cleats fastened to the underside of the vanity top.

NOTE: I tried to remove the entire vanity first. This turns out to be nearly impossible without substantial damage, even after removing the vertical cover section around the mast support, so I chose to cut the vanity in two instead as the easier route. The screws cleating it to the inside wall are the problem -- they're all buried underneath the laminate. If you plan to replace or recover the entire vanity then this won't be a problem. )

4. On our boat the switch for the shower pumpout had to be relocated inboard a few inches to clear the tank.

5. Remove clips and hose on the wiring passing thru the tank space so that it moves freely and can lie flat against the bulkhead.

6. Cut away the inverted U section fiberglass in this same area, down to 25-3/4" from the vanity top and out to the outboard wall. Make sure that the top edge remaining is level in the boat (e.g parallel to the counter top.) This is the most time consuming part and seems to go better done in stages rather than all at once. A dremel tool with a fiber cutoff wheel (~ $50) did most of the work for me, aided by a hacksaw blade in a handle. The dremel tool got resin dust everywhere -- close off and cover everything you don't want covered with it. Wear a mask and safety glasses, of course.

7. Cut out a 25-3/4" high by 12" wide opening in the outboard wall for the outboard end of the tank to fit into. It will just barely project into the lower outboard locker. More dremel tool plus hacksaw blade work.

CONSTRUCTION AND REPLACEMENT

8. Screw or bolt 18" x 3/4" x 1-1/2" wood cleats to the main cabin bulkhead and upper fiberglass edge leftover from the U section. Locate the top surface of these cleats 25-3/4" down from the vanity counter top and level side-to-side within the boat (i.e. parallel to the counter top.) (I actually made my forward cleat of 2"x2" stock and extended it the whole width of the bathroom to add strength to the floor and the boat's bulkhead structure. Our boat can experience quite rough conditions at times.) Gluing these cleats as well as fastening them is also a good idea -- I used polyurethane glue with good results.

9. Make a 12" x 24" platform for the tank of 1/2" plywood and screw it onto the top of these cleats. The strength of this platform replaces that of the original fiberglass that you have cut away to prevent movement fore and aft of the bathroom floor. (The 2"x2" full-width cleat also helps with this.) It also supports the tank bottom fully with a non-abrasive support as recommended by the tank manufacturer. I did not glue this platform to the cleats so as to be able to remove it if necessary at some future point.

10. Smooth, round and cover with duct tape any rough fiberglass edges or surfaces that might cut the tank as it rubs back and forth against them when the boat pitches and rolls. The dremel tool and cutoff wheel are very handy here again, along with sandpaper, grinding wheels, etc.

11. Try the tank for fit. (NOTE: Either without any hose couplings in place, or only with the port (outboard) inlet and outlet hose couplings in place. It won't fit with the vent coupling or the inside outlet couplings in place. These have to be screwed in after it's in place.) The tank will only slide in one way, as shown in the picture. Trim any places that prevent the tank from going into place.

12. Screw or bolt two vertical 24" x 3/4" x 1-1/2" wood cleats against the main cabin bulkhead (aft side of the tank) that make a tight fit to its aft inner and out vertical edges when it's in place. These, along with two more on the vanity front, restrain the tank from side-to-side movement as the boat rolls.

NOTE: Making the tank by itself fit rigidly in place, without movement, means that the hose fittings will not be depended on to help restrain a full tank (150#'s of waste!), reducing the possiblity of leaks.

NOTE: All of the four restraining cleats mentioned here and below are best made of smooth planed clear softwood (e.g. fir porch flooring) to minimize abrasion of the tank.

13. Reinforce the 26" edge of the tank opening in the outside wall (forward, near the toilet) with a 2"x2" cleat on the outboard side, in the locker. This one must clear the tank by a small amount, allowing the tank to be inserted and removed. I glued this cleat in place as well as bolting it to prevent any chance of breaking this now-rather-fragile panel of fiberglass, in case someone should strike it or fall against it. The tank restraining cleat will be fastened to this one once the tank is in place. I also added a cleat on the lower edge of the locker opening in this panel (over the toilet). It had never had one and looked like it could use it as well. The upper edge of the flap opening had been cleated by Pearson.

14. Test fit the tank again and make, fit, and fasten a cleat to restrain the tank at its foward outboard edge. This is the cleat referred to in the previous step. Remove it to remove the tank. (NOTE: Do not glue this cleat in place, only screw or bolt it. It must be removed to insert and remove the tank!)

NOTE: Watch when drilling that fasteners at right angles in the 2"x2" cleat in step 13 do not intersect one another!

15. Put the tank in place for the final time.

NOTE: In our boat the upper section of the tank was held out from the cabin bulkhead (aft side of the tank) by the approximately 3/4" thickness of the fiberglass U section leftover along the wall at the bottom. (See pictures.) Arrange the wiring flat in this upper free space so that it is not chafed by the tank, which would be a potential fire hazard. An envelope of thick (e.g. 6mils) polyethylene (Home Depot material) around the wires is a good idea allowing wires to be added or removed after the tank is in place but protecting them from chafe by the tank. I wouldn't recommend duct taping or clamping the wires in place as that would prevent later changes to the wiring.

16. Fit the removed vanity section back into place. Trim as necessary.

17. Make up a 25-3/4" x 1-1/2" x 1/2" trim piece ( e.g. teak, to match the fiddles on the vanity) to cover the vertical joint between the two sections of the vanity. Locate this on the outside to cover the joint and through-bolt it through a cleat on the inside wall of the stationary section of the vanity. This inside cleat must make a tight fit to the tank to complete the side-to-side restraint of the tank. The outside piece also holds the two vanity vertical sections together and completes restraint of fore and aft movement of the inboard end of the tank. It must be strong! I used Ipe wood, left over from a deck job, that looks much like teak, and is even stronger.

18. Make and fit a 25-3/4 x 1" x 1" trim and cleat piece (teak or similar again) to cover the vertical joint between the vanity and the outboard wall, and to restrain the tank (and vanity front!) from forward movement when the boat pitches. This piece screws or bolts into the reinforcing cleat on the outside of this edge of the wall (step 13) capturing the fiberglass in between them. Watch that fasteners don't intersect.

19. Refasten the cleats on the underside of the removed vanity top to the bulkheads etc.

20. Trim the joint in the counter top with aluminum or plastic counter joint covering (Home Depot item.)

21. Add quarter round or other trim to the counter-wall joints as desired and refinish any blemishes due to removed screws etc. in the laminate with mix-n-match gelcoat patch from marine stores.

22. Replace the toilet, vanity door, and lower outboard locker flap.

23. Screw in hose couplings and connect hoses to the tank inlet, pumpout fittings and vent.

24. The tank level (the tank is translucent) can be checked conveniently at any time by opening the vanity door -- no complicated gauging necessary.

OTHER CONSIDERATIONS

While doing this work I also cut out a rectangular area in the top of the fiberglass U-section beneath the washbasin. By leaving a flange all around the cutout the U-section is not significantly weakened. I installed a new 1-1/2" thru hull below this opening. This becomes the only outlet needed in the boat for the bathroom, handling the toilet when the tank is bypassed, the tank internal pumpout, the washbasin (which was draining into the toilet before this!) and the shower pumpout, allowing a net reduction in the number of thru-hulls. This outlet location also keeps water hoses, pumps, etc. out of other, otherwise dry, lockers in the boat, something that appeals to me. It's easily accessible for opening and closing the seacock and inspection. Pumps are all relocated to this space as well, freeing up valuable locker space. In some of the pictures you can see the new thru-hull and some of its plumbing. Some of these hoses run beneath the tank, as noted at the beginning. I also like the fact that this change has made accessible an area of the boat's hull that was previously totally inaccessible. Plumbing for the washbasin and shower is now much easier to install and service, and the access to the foot of the mast and its support is greatly improved. I can recommend this change to all P35 owners.