Planning the plumbing!

Oct 26, 2008
6,041
Catalina 320 Barnegat, NJ
Wanting to make some improvements to my sanitary system, I looked in all the nooks and crannies to trace the sanitary hoses. I noticed something that seemed odd that I hadn't noticed about 10 years ago when I replaced hoses or even a few years ago when I replaced the y-valve. I've recently had problems with the pump valve which allowed wastewater to leak back into the bowl after flushing. I was surprised by the amount. Mind you, our waste system gets extremely light use.

As it turns out, the discharge hose from the toilet makes a loop about 5' long to the y-valve. From there, one port leads directly to the overboard discharge with no ventilated loop. The other port makes a vertical rise with newer hose to the ventilated loop and down into the holding tank. I've looked in numerous diagrams and they all show a ventilated loop above the overboard discharge and none between the toilet and the tank. Has mine been connected wrong all this time?

Before anybody thinks that I reversed the hoses, I don't think that's possible. First, I never changed out the overboard discharge hose. It's still the black-walled Shields S-101 that the boat came with and the hose isn't anywhere near long enough to connect to the ventilated loop. I changed out the other hoses with white vinyl Shields S-148 and followed the original configuration as far as I can tell. I also replaced the v-loop and it is in the original location.

I have always had a very slight odor problem. It is noticeable when I first open the boat but dissipates with ventilation. I've always been troubled why I can't get rid of it completely. Is the fact that the tank is connected to the v-loop part of the answer? I think the amount of water backing into the bowl is more explainable. There is probably at least a 6' column of water in the 1.5" hoses below the loop. That's about a half gallon, not enough to overflow the bowl but enough to fill it substantially.
 
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Feb 20, 2011
7,990
Island Packet 35 Tucson, AZ/San Carlos, MX
I have always had a very slight odor problem. It is noticeable when I first open the boat but dissipates with ventilation. I've always been troubled why I can't get rid of it completely. Is the fact that the tank is connected to the v-loop part of the answer? I think the amount of water backing into the bowl is more explainable. There is probably at least a 6' column of water in the 1.5" hoses below the loop. That's about a half gallon, not enough to overf
Usually odors can be traced to hoses as they age. You say you've replaced them? What's the tank made of?
The backflow could be saying it's time for a new joker valve.
You didn't mention what brand of toilet you're working with. The manufacturer should have guidelines...
 
Oct 26, 2008
6,041
Catalina 320 Barnegat, NJ
Yes, the hoses were originally very bad. When I bought the boat, I naively thought that the odor would not be difficult to eliminate. I learned my lesson … I'll never buy a boat with an odor again if I can help it! I replaced the vinyl hoses and the toilet because the smell was brutal. At the time, I was able to get a W-C Headmate, before they discontinued. The tank is plastic. I thought for a while that I would need to replace it, but cutting a giant hole in the v-berth floor to get it out and new one in doesn't seem worthwhile. I've been able to clean and sanitize the tank so I don't think it is a problem. The discharge hose to the thru-hull was the black-walled rubber hose and it doesn't smell, so I left it alone. The newer vinyl hoses are at least 10 years now but I don't detect odor, but I'm ok with doing a total overhaul. I want to make wholesale changes - but I still won't remove the tank, I think, even tho it only holds 10 gallons.
 
Jan 11, 2014
11,321
Sabre 362 113 Fair Haven, NY
Tanks usually don't permeate, so it is unlikely the smell is coming from the tank. However, the the seal for the inspection port might be a culprit and the vent hose, especially if it is vinyl is a prime candidate.

There is no need for a vented loop in the hose to the holding tank, unless the tank is higher than the head and the inlet goes directly to the bottom of the tank. There does need to be a loop in the hose that goes above the top of the tank so everything drains down into the tank.

The overboard discharge needs a vented loop to prevent siphoning from ocean if the head is below the water line.

Use the wet rag test on the hoses and tank to see if the hoses have permeated.
 
Jan 4, 2006
6,444
Hunter 310 West Vancouver, B.C.
See replies #4 and #7 to put your mind at rest about plastic tanks.

 
Oct 26, 2008
6,041
Catalina 320 Barnegat, NJ
There is no need for a vented loop in the hose to the holding tank, unless the tank is higher than the head and the inlet goes directly to the bottom of the tank. There does need to be a loop in the hose that goes above the top of the tank so everything drains down into the tank.
That's what I thought. I could swear that the installation that I found when I bought the boat would be the original installation. Why in the world would Wellcraft put the v-loop to the tank and run the alternative hose directly to overboard? Was it installation error? It didn't matter that the overboard discharge wasn't on the v-loop. We never had the thru-hull valve open anyway. But I'm thinking that the discharge hose into the tank is like a vent directly into the boat thru the v-loop. Isn't that vent open when there is no water pushing thru? To me, it explains a lot. I did all I could to eliminate odors (replaced the foul hoses, replaced the vent hose, replaced the toilet, cleaned and sanitized the tank - the inspection port didn't exist until I made one), yet just a slight whiff persisted after all the work was done. The v-loop is behind cabinet doors behind the hull liner.

I'm convinced I've discovered a defect that shouldn't exist. I'm looking forward to changing the hoses, this time with my own routing. There is no reason why the hose leading to the y-valve should be 5' long and wind thru a bulkhead under the v-berth and then back thru the bulkhead to the valve. Instead of 5', I should need less than 18" of hose. Then the hose to the tank will be just 24" or so, instead of going up and around the v-loop. At one location, I have 4 hoses going thru a bulkhead, where I should be able to reduce it to 3. Original layout was very inefficient and just plain wrong!
 
Jan 11, 2014
11,321
Sabre 362 113 Fair Haven, NY
Earlier I posted a link to an article on SV-SecondStar.net about a holding tank refit. If you visited the page, the photos might not have visible. It is fixed now.