Sea Hunt,
For about 8 years I had no problems with the head. Then I started to have odor problems, two actually.
The first was that what is essentially sewer gas leaking into the boat through the inspection plate threads on the inspection plate on the holding tank - leaking into the boat because the tank was pressurized. Why was it pressurized? Because the vent fitting at the end of the vent hose had become corroded inside so the tank was not actually vented, it was sealed. Problem solved with a little coat hanger wire and fiddling around with the vent fitting at the stern. I was proud to have solved this problem so simply.
However, the subsequent year I kept having holding tank odor of a minor but consistent nature while racking out on the port settee - under which the waste line runs. My guests had the same experience, unfortunately. Turns out that the 30 year old hose under the settee had become permeated with tank odor while the system was pressurized the previous year. Solution: replace the hose which I did, but I used the best hose I could find (
http://marine.dometicgroup.com/en/holdi ... m_2789.php). The hose is stiff but flexible enough to make the bends needed. A heat gun is needed to gain enough flexibility to get the old hose off and the new one on - but all together is was less than an hour job.
I think this is a simpler way to make this adjustment than PVC.
So I have three items of advice
- annually check to be sure the tank is ACTUALLY vented
- replace hose from head to tank
- rebuild/replace head pump. In my case I dispensed with pump rebuilding because I am lazy, and the cost of a new pump was not that much more than a new head - so I simply bought a new head from Groco and bolted to the floor and connected the hoses. I wasn't having any problems with it - but know it was original and probably unserviced since 1984.
This is actually a system on the boat that an owner with minimum skill can perform. It is just important to address ALL elements of the system - once your boat has a new system, you will not need to touch it except for regular maint. The next upgrade will be the responsibility of the NO (Next Owner).