DON'T connect your drinking water to the head!
You MUST NOT EVER connect your head to your drinking water system!You WILL need to install a black water tank somewhere (I believe that the C-27s had theirs under the vee berth, but it may have been under a settee), a through deck fitting to pump that bugger out, and a vent hose (Catalina usually vented through one of the lifeline stancions (sp?)).DON'T use a recycled drinking water tank as the black water holding tank. If you do, your boat WILL smell like a sewer. The black water tanks are thicker construction (and usually black in color) and less likely to leak. Contact Catalina Yachts for more information. They can tell you where they put the holding tanks on your model boat, and possibly provide you with the dimensions / source for that tank. To flush with fresh water (read that drinking water), most people either pour the water out of a container (quart bottle, etc) into the head directly, or "T" the head water supply into the head sink drain. With the head sink drain through hull closed, you run some water into the sink and use that to flush the head. That's the way my '87 C-30 was plumbed.You MUST have an air gap between the fresh water system and the head. Both of these two options provide that gap.Finally, before all else fails, write a note to the Head Mistress on this web site. She apparently knows all.SteveAlchemist C-30T #4764Alchemist C-320 #909