Just wanted to share a great modification to the Hunter 31 (1984) holding tank plumbing. About two years ago I replaced the hoses with top quality Trident and Poly-X (hard task because of the small space between the hull and the liner where three hoses need to pass in the space for two). While it worked great initially, I started getting odors again recently. It turns out that the connection from the tank to the waste discharge through hull is always wet so the waste will permeate the hoses no matter the quality. So much about Trident hose being odor free.
I replaced the discharge hoses with 1 1/4" PVC tubing. I installed a T with a screw cap for the eventual connection to the deck discharge. Then I decided against using a manual discharge pump as I thought the waste tank level was about even with the waterline so with proper routing it should drain by gravity. Connected everything, filled the waste tank with water, opened the through hull, it trickled but the tank stayed mostly full. It turned out I forgot a paper towel stuffed in the tank discharge port while I was working on the tubing. Poor me. Now I have no way of emptying the tank as the deck connection is not fitted yet while the T-is below the water level. Next, I connected a dinghy inflation pump to the tank vent hose - it worked like magic, pressuring the tank a bit and the contents and the paper towel went out fairly quickly. The dinghy pump will empty the tank all the way to the thru hull and if you close the valve before switching off the pump, it will stay totally dry, so I could work on the T and the deck connection. Plus, I know that my system is air tight as there was no air escaping from anywhere.
The lesson is, the Hunter 31 waste system, as designed, is very easy to modify for gravity drain. There is about an inch of liquid in the tank with the thru hull open. Since the tank is fiberglass and with PVC tubing there is nothing that can be permeated now. May be the rubber connectors I use to connect the tube to the hose fitting but these are easy to replace and I think rubber is resistant to odor. The only downside to this modification is that eventually it may clog since the tubing is not straight line but has knees and 45s. However, if offshore the trick with the dinghy pump works fairly well and the pump out is so powerful it would suck anything out in no time.
The more I think about it, there is no way to prevent waste sitting in the discharge hoses with a waste pump on any boat. May be if you have PVC tubing going up from the tank discharge port, then the pump, then a hose straight down to the thru hull, so that sea water will dilute the contents until it is less corrosive. That would have been difficult to do on my boat and on most boats I guess. I really recommend PVC tubing for anyone looking for a permanent waste odor fix. Not to mention that the cost of PVC tubing relative to replacing Trident hoses every two years is minimal. The other thing about gravity drain is that there are no Y-valves or pumps to play with or switch. Once done it is use and forget.
SV Pizzazz
I replaced the discharge hoses with 1 1/4" PVC tubing. I installed a T with a screw cap for the eventual connection to the deck discharge. Then I decided against using a manual discharge pump as I thought the waste tank level was about even with the waterline so with proper routing it should drain by gravity. Connected everything, filled the waste tank with water, opened the through hull, it trickled but the tank stayed mostly full. It turned out I forgot a paper towel stuffed in the tank discharge port while I was working on the tubing. Poor me. Now I have no way of emptying the tank as the deck connection is not fitted yet while the T-is below the water level. Next, I connected a dinghy inflation pump to the tank vent hose - it worked like magic, pressuring the tank a bit and the contents and the paper towel went out fairly quickly. The dinghy pump will empty the tank all the way to the thru hull and if you close the valve before switching off the pump, it will stay totally dry, so I could work on the T and the deck connection. Plus, I know that my system is air tight as there was no air escaping from anywhere.
The lesson is, the Hunter 31 waste system, as designed, is very easy to modify for gravity drain. There is about an inch of liquid in the tank with the thru hull open. Since the tank is fiberglass and with PVC tubing there is nothing that can be permeated now. May be the rubber connectors I use to connect the tube to the hose fitting but these are easy to replace and I think rubber is resistant to odor. The only downside to this modification is that eventually it may clog since the tubing is not straight line but has knees and 45s. However, if offshore the trick with the dinghy pump works fairly well and the pump out is so powerful it would suck anything out in no time.
The more I think about it, there is no way to prevent waste sitting in the discharge hoses with a waste pump on any boat. May be if you have PVC tubing going up from the tank discharge port, then the pump, then a hose straight down to the thru hull, so that sea water will dilute the contents until it is less corrosive. That would have been difficult to do on my boat and on most boats I guess. I really recommend PVC tubing for anyone looking for a permanent waste odor fix. Not to mention that the cost of PVC tubing relative to replacing Trident hoses every two years is minimal. The other thing about gravity drain is that there are no Y-valves or pumps to play with or switch. Once done it is use and forget.
SV Pizzazz
