This post begins as I am sure many posts on this forum do with the "I have a smell ..." line. But before you all cry 'read this' and 'read that' I believe I know why I have a smell and I think I know some of the 'what' that I need to do about it. But first let me describe the boat.
The boat is a 2001 3 cabin Beneteau 381, single head model. Orientation wise there are two aft cabins and the head is to port of the companionway steps - pretty stock there as current boats go - also see hyperlink below for a schematic. However because of the 3 cabins and the limited space Beneteau elected to install the holding tank under the swim platform - very creative on their part. The hose from the head runs under the sink in the head, through the clothes locker in the port aft cabin, alongside the berth (underneath the shelf that is glassed into the side of the cabin) and into the area behind the cabin underneath the propane locker / swim platform. Beneteau have managed to squeeze in a meagre 14 gallon tank, that from what I can tell with a tape measure 'just' fits through the access panel cut into the rear bulkhead of that stateroom. There is no other access to this space without cutting away large amounts of fiberglass or hacking into the finished interior woodwork - neither of those things is happening on this boat.
My smell appears to be caused by bad threaded fittings in the tank itself and as I look closer there appears to be some form of adhesive or sealer in the threads and is allowing odor to permeate.
The fact that there is odor at all (despite switching to KO and a good flush of the system) is I think due to the long run from the head and inadequate venting.
Surprisingly the feed pipe that runs almost 15ft from the head to the tank - black thick walled rubber type head hose does not smell so I assume it is not permeated (thankfully). However I am agog at what I see as a design flaw - in order to clear this pipe of any and all matter that could cause odor problems we have to flush through about 3 gallons of water per flush - with a 14G tank that can pose a problem as you can imagine so it doesn't happen as often as it should.
My plan is to remove the tank this winter and replace with as large a tank as I can get in there (both in the actual space as well as through the cutout in the aft cabin panel) - noting that this may mean only a marginal increase in capacity if any and then to replumb - basically in the same configuration I have now but with new fittings and hoses. At the same time I plan to install dual 5/8" or 3/4" vents to provide sufficient air for aerobic decomp to occur and to vent each of these in as straight a line as possible to the port and starboard aft portions of the boat with new vent fittings (without gauze screens on them).
My question is two fold :
1. Does anyone have a 3 cabin 381 and happen to have installed a larger tank and can share that process, specifically the size and type of tank you managed to get in there? This would save me a lot of measuring and plywood tank mockup building this winter.
2. Does anyone have any suggestions for my 15ft run of pipe and how I might address that - note I cannot find anywhere in the head or aft cabin to install the tank closer to the head.
Note there is a schematic of the boat layout here : http://www.poseidoncharters.com/greece/images/Cyclades393layout.gif The head as you can see is to port of the companionway. Directly in front of it is the built in fridge / freezer so that space is not useable. Underneath the port aft berth is the built in fresh water tank and the holding tank is in the tail of the boat. I don't see anywhere else in the boat that I can install a tank that does not create at least as much of an issue as I currently have with hose run. If it were up to me, holding tanks would always be a graviy feed underneath the head and all the tank fittings would be on the top. But that's just me.
Thanks in anticipation.
Mark
SV Calypso, RI.
The boat is a 2001 3 cabin Beneteau 381, single head model. Orientation wise there are two aft cabins and the head is to port of the companionway steps - pretty stock there as current boats go - also see hyperlink below for a schematic. However because of the 3 cabins and the limited space Beneteau elected to install the holding tank under the swim platform - very creative on their part. The hose from the head runs under the sink in the head, through the clothes locker in the port aft cabin, alongside the berth (underneath the shelf that is glassed into the side of the cabin) and into the area behind the cabin underneath the propane locker / swim platform. Beneteau have managed to squeeze in a meagre 14 gallon tank, that from what I can tell with a tape measure 'just' fits through the access panel cut into the rear bulkhead of that stateroom. There is no other access to this space without cutting away large amounts of fiberglass or hacking into the finished interior woodwork - neither of those things is happening on this boat.
My smell appears to be caused by bad threaded fittings in the tank itself and as I look closer there appears to be some form of adhesive or sealer in the threads and is allowing odor to permeate.
The fact that there is odor at all (despite switching to KO and a good flush of the system) is I think due to the long run from the head and inadequate venting.
Surprisingly the feed pipe that runs almost 15ft from the head to the tank - black thick walled rubber type head hose does not smell so I assume it is not permeated (thankfully). However I am agog at what I see as a design flaw - in order to clear this pipe of any and all matter that could cause odor problems we have to flush through about 3 gallons of water per flush - with a 14G tank that can pose a problem as you can imagine so it doesn't happen as often as it should.
My plan is to remove the tank this winter and replace with as large a tank as I can get in there (both in the actual space as well as through the cutout in the aft cabin panel) - noting that this may mean only a marginal increase in capacity if any and then to replumb - basically in the same configuration I have now but with new fittings and hoses. At the same time I plan to install dual 5/8" or 3/4" vents to provide sufficient air for aerobic decomp to occur and to vent each of these in as straight a line as possible to the port and starboard aft portions of the boat with new vent fittings (without gauze screens on them).
My question is two fold :
1. Does anyone have a 3 cabin 381 and happen to have installed a larger tank and can share that process, specifically the size and type of tank you managed to get in there? This would save me a lot of measuring and plywood tank mockup building this winter.
2. Does anyone have any suggestions for my 15ft run of pipe and how I might address that - note I cannot find anywhere in the head or aft cabin to install the tank closer to the head.
Note there is a schematic of the boat layout here : http://www.poseidoncharters.com/greece/images/Cyclades393layout.gif The head as you can see is to port of the companionway. Directly in front of it is the built in fridge / freezer so that space is not useable. Underneath the port aft berth is the built in fresh water tank and the holding tank is in the tail of the boat. I don't see anywhere else in the boat that I can install a tank that does not create at least as much of an issue as I currently have with hose run. If it were up to me, holding tanks would always be a graviy feed underneath the head and all the tank fittings would be on the top. But that's just me.
Thanks in anticipation.
Mark
SV Calypso, RI.
)
