Originally Posted by CaptTom
The aft one I replaced. I know that is only 15 Gallons. It's under the sink, behind the drawers. Horrible location, no way to get anything larger in there.
The forward one is probably about the same size, under the v berth on the port side, just forward of the bulkhead for the head.
I notice that both heads had some major lay-out changes in later models. There was also a galley-down design. Mine has galley up, v berth forward, aft of that is the head to port and stowage to starboard. The aft head has the sink on the far left-hand side as you enter. I think that changed later, too.
I think your layout is the same as mine. In the aft head the Lectra San unit was under the sink, behind the drawers. The other Lectra San unit was under the v berth on the port side, just forward of the bulkhead for the head. Both seem to have been in the same location as your holding tanks.
One option I considered was replacing the Lectra San units with holding tanks in the same location. I think the forward head would have been fine. But the aft head was a concern because the bottom of toilet was only about 7 inches above where bottom of the holding tank would be under the sink. I just couldn't see getting a proper downhill flush into a tank in that location.
So once I started looking in the engine room it opened up other location possibilities. The down side was it was going to be much more work. But the up side was a larger single holding tank.