Catalina 270 Holding Tank Replacement (11/2016)

Not the first major maintenance job I wanted to tackle but not much choice! I noticed the holding tank leaking after a few weekends of using the boat (and a few trips to the pumpout station).

First action was to go back to the pumpout station and empty the tank and then refill it with water many times over to get it as clean as possible. Then disassemble and remove everything.

A few things I found:

The tank vent is inadequate on several counts. Most recommendations I've found state the vent should:
  1. Have no traps that can hold sewage and block the vent
  2. Be 1" in diameter
The OEM vent doesn't meet either criteria.

1. The tube from the tank goes down towards the area under the V-berth and then back up to the deck, so there is a long-ish area which can trap water/sewage to completely block the vent.

2. The hose is 3/4", a bit smaller than 1" but should be fine... except that it ends in a bolt which goes inside a stanchion tube. The diameter of the hole in this bolt is only 6.8mm (about a quarter inch) but it gets worse because on the stanchion there are only two tiny little holes to serve as vents! So for most practical purposes, the tank was not really vented.


3. Instead of a Y-valve to divert toilet discharge to the tank or outside, there is a household brass valve to shut off the pipe going to the holding tank. Needless to say, this brass valve was frozen in place by corrosion.

4. None of the hose fittings were barbed.

There is evidence of some leakage from the vent pipe where it connects to the stanchion (it did not seal tightly).  The intake hose and the macerator pump showed no evidence of leakage.  I also noticed the vent fitting is very close to the edge of the hole (picture below is with new tank as I forgot to take a photo earlier, but it was the same). There is a small stress crack in the fiberglass there which suggests the fitting might've been hitting the edge when the tank moved (nothing really hold the tank down other than its weight and the stiffness of the attached hoses).

I could not identify the source of the primary leak until later. The guilty party was the Jabsco macerator pump! It was leaking internally from its housing where the two halves join. I only discovered this after putting the new system together and started testing it with clean water (fortunately!). Searching the web, looks like many people have had similar leaks from the pump body. So if you have a mystery leak, suspect the pump first!


Not strictly related to the holding tank work but since I had all the floorboard out, first thing I did was paint the bilges:

Then I ordered a new holding tank from Catalina Direct. The tank is same as original, with two changes:
  1. I had a 1" fitting installed for the vent (instead of 3/4")
  2. All the fitting are now barbed
Here is a diagram with measurements of the OEM tank.

Then I added a 1" through-hull for the vent hose:

In order to avoid the water/waste trap caused by the vent hose going downwards from the tank before going up to the vent, I installed a PCV tube as seen on the photo below. The vent hose can now go straight out from the tank and then up, so there is no water trap in it. This should help keep the vent hose open for ventilation.

I replaced all the hoses.
  1. 15ft of Trident 1.5" sanitation hose
  2. 12ft of 1" hose for the vent
  3. 12ft of 3/4" hose for the water intake
  4. 2ft of 1" hose for the macerator outlet
After some debate, I ended up plumbing the toilet straight to the holding tank. I did not install a valve to close it nor a tee to the through hull. Fewer moving parts and more importantly fewer potential leak points.

Back to my Catalina 270 page.