I think your dimension estimates are on the large side, but don't have better data to support that without actual measurements. I do know there is no way the holding tank is larger than the potable water tank, which on Rhapsody is 18 Gallons.

Other Data to support the Tank Capacity:
Hull #371 - 14 Gallon Holding Tank
Hull #512 - 10 Gallon Holding Tank
Hull #80 - 12 Gallon Holding Tank
Hull #444 - 10 Gallon Holding Tank

I'll throw in an extra gallon on the largest shown just for you and call it an even 15....

I think mine is 12 - 15 gallons. I know 8-10 flushes is about max before I like to off load when I am cruising.

Anyway I was really just wondering if anyone had done this - I think I will just replace with what I have.

I'm curious if the post '84 models have larger tanks. Mine fills almost the entire forward storage compartment under the v-berth. To my eye, it appears to be significantly larger then the two water tanks combined. Is that what the earlier models have?

Steve - there very well could be a difference in model years and explain why our perceptions on tank size are so different. I've attached a picture of the space between the aft end of the holding tank and the bulkhead on the aft end of the space. The tank occupies about the forward third of that space and flits flush against the bulkhead by the anchor locker. You can estimate dimensions by scaling from the size of the hose (1-3/4" OD) and the 8-1/2" x 11" paper chart taped on the tank.

You also mention two water tanks. Hull 348 only has a single 18 gallon polypropylene water tank under the port settee.

If Rod Johnstone calls in for the BOG meeting on 24 March, I'll ask him what he knows about the tank sizes.


Sanitary Piping Diagram & Valve Lineup

Great picture-it's possible that my memory may be flawed. I'll have a look this weekend. By the way-that is an immaculate (and complicated) set of hoses!

The picture is exactly like mine. Except you could not eat off it as you could Bill's.

following is my "Rules Interpretation" on this issue

A holding tank is required with a capacity equal or greater to the original equipment (about 14 gallons) The tank must be located in the same location as the original tank. Bladder tanks are an acceptable alternative. Installation for discharge must be in accordance with the current federal and state laws

LimeLight hull 51 has a bladder, 14 gal It was installed in the early 90's. And seems to be working just fine and is good for racing. However up in Canda BC there isnt has many pump out as there is in the USA and we find 14 Gal to be a bit small when we are cruising. Thinking about putting in a tank with larger capacity 20 to 25 gal for those summer trips, plus I am not sure what the shelf life of the bladder is and wouldnt want it to fail.