I am working on my plans to install "the last holding tank I'm ever going to install". Material choice seems to be quite controversial with advantages, but more importantly, potentially serious DISadvantages to the various materials - poly, aluminum, stainless, and fibreglass. I' more or less narrowed it down to poly or stainless, and the two big disadvantages that seem to be prevalent (other than cost of stainless, but I can live with that) are: the seemingly perpetual odour that exists with every poly tank installation I've seen, vs the crevice corrosion issues in the welds in the stainless tank. I've read your articles on odour prevention, and while I'd like to think I may get lucky and actually succeed, from a planning perspective I'd like to plan for worst case, which means odour will exist. Can you comment? For plumbing, it occurred to me to use white pvc (sched 40) for as much of the run as possible. Would this not be at least as odour-proof as the SeaLand "bullet-proof" hose? (And hugely less expensive.) Because of boat layout, I'm likely looking at a discharge run of 20' or so including twists and turns. Thx for any wisdom.........Randy
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Peggie Hall/Head Mistress
Go with poly...
Good quality thick-walled (at least 3/8") won't stink, I promise. Mine was under my v-berth...never a trace a odor from the tank, and it was 21 years old when I sold the boat. heck Ronco Plastics...they make TOP quality, thick-walled roto-molded tanks, and have more than 400 shapes and sizes--over 100 of which are non-rectangular--to choose from..and for a VERY reasonable price. And you can spec your own fittings sizes and locations, to be installed by them when the tank is made. Their catalog is on their website at: http://www.ronco-plastics.com They're great people to work with, and a tank from them will cost you about 1/4 of what it would cost to have a stainless tank--which WILL leak at a seam or fitting within 2-5 years, and turn into a collander in about 10--made. However, I think you have another problem: 20' from the head to the tank and/or a thru-hull is at least twice as far as it should be. 6-8' of total hose run is the optimal distance...10 is the absolute maximum. Longer, and waste sits in the pipe or hose to either permeate the hose or clog hard pipe. Hard pipe should only be used for long straight runs, because every joint creates a "bump" in the hose that traps solids and paper. Hard pipe should should always be soft-coupled to anything else in the system that's rigid (toilet, tank, seacock, macerator) with 8-12" of hose...never be connected directly. Boats flex, and they take a pounding sometimes...the hose acts as a shock absorber. Without it, the weaker side of the connection can crack. So methinks we need to find another location for the tank that's a LOT closer to the toilet--and with 400 molds to choose from, I'm pretty sure we can--and think in terms of possibly a mix of hard pipe and hose (I wouldn't go with anything but SeaLand OdorSafe) for the plumbing. Hard pipe bends so little, and any straight run shorter than 3' doesn't really make hard pipe very practical.
Good quality thick-walled (at least 3/8") won't stink, I promise. Mine was under my v-berth...never a trace a odor from the tank, and it was 21 years old when I sold the boat. heck Ronco Plastics...they make TOP quality, thick-walled roto-molded tanks, and have more than 400 shapes and sizes--over 100 of which are non-rectangular--to choose from..and for a VERY reasonable price. And you can spec your own fittings sizes and locations, to be installed by them when the tank is made. Their catalog is on their website at: http://www.ronco-plastics.com They're great people to work with, and a tank from them will cost you about 1/4 of what it would cost to have a stainless tank--which WILL leak at a seam or fitting within 2-5 years, and turn into a collander in about 10--made. However, I think you have another problem: 20' from the head to the tank and/or a thru-hull is at least twice as far as it should be. 6-8' of total hose run is the optimal distance...10 is the absolute maximum. Longer, and waste sits in the pipe or hose to either permeate the hose or clog hard pipe. Hard pipe should only be used for long straight runs, because every joint creates a "bump" in the hose that traps solids and paper. Hard pipe should should always be soft-coupled to anything else in the system that's rigid (toilet, tank, seacock, macerator) with 8-12" of hose...never be connected directly. Boats flex, and they take a pounding sometimes...the hose acts as a shock absorber. Without it, the weaker side of the connection can crack. So methinks we need to find another location for the tank that's a LOT closer to the toilet--and with 400 molds to choose from, I'm pretty sure we can--and think in terms of possibly a mix of hard pipe and hose (I wouldn't go with anything but SeaLand OdorSafe) for the plumbing. Hard pipe bends so little, and any straight run shorter than 3' doesn't really make hard pipe very practical.
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fred miller
Poly tanks Pro and Con
Been there and done that at least 3-4 times over the years. First, it is true poly will hold odor . . period and it will not come out no matter what you do. Odors also permeate the tank walls. On a positve note they will not corrode and are relatively inexpensive.Stainless and aluminum have welding issues to address. The tank walls are usually not the problem as far as leakage and they are are odor proof. Personnally, I opted to keep the orginal aluminum tank, removed it and rewelded all the seams. Its fine and no odors. Periodically you should neutralize the tank after perhaps every 6-8 pumpouts.I use a an acid neutralkizing agent / white vinegar. I dump a gallon in through the pump out, mix with water and then pump it out. As far as Sched 40 piping, I only recommend it for the long straight runs. Make sure all the elbos, joints and connections however are hose. Rigid PVC cannot take any kind of movement or the joints break free. Good Luck FM s/v M Squared
Been there and done that at least 3-4 times over the years. First, it is true poly will hold odor . . period and it will not come out no matter what you do. Odors also permeate the tank walls. On a positve note they will not corrode and are relatively inexpensive.Stainless and aluminum have welding issues to address. The tank walls are usually not the problem as far as leakage and they are are odor proof. Personnally, I opted to keep the orginal aluminum tank, removed it and rewelded all the seams. Its fine and no odors. Periodically you should neutralize the tank after perhaps every 6-8 pumpouts.I use a an acid neutralkizing agent / white vinegar. I dump a gallon in through the pump out, mix with water and then pump it out. As far as Sched 40 piping, I only recommend it for the long straight runs. Make sure all the elbos, joints and connections however are hose. Rigid PVC cannot take any kind of movement or the joints break free. Good Luck FM s/v M Squared
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Peggie Hall/Head Mistress
Fred, I have to disagree...and agree
You're right that cheap thin-walled tanks made from low grade low density poly will permeate...although they usually fail before that happens. The walls aren't strong enough support the weight of the contents, they bulge, flex and ultimately crack...usually in a few years. But often what is believed to be a permeated tank is actually leaking at fitting...just not quite enough to allow any liquid to escape, only gasses. 'Cuz when a tank bulges, the walls stretch pulling female fitting ports out of round. Bulging and stretching also thins the tank material, and the thinner the material, the faster it permeates. Good quality thick-walled tanks will also permeate--eventually. However, it takes decades, not just years, for permeation to make it all the way through the tank. Better quality poly, medium density instead of low, better curing and quality control are partly the reason, but also because the walls are strong enough to support the weight of the contents, there is no bulging or stretching...no weakening of the tank. In the more than 15 years that I sold tanks--and the 3 years since I sold my company, but still am asked to locate and solve odor problems--I've yet to see a good quality, thick walled poly tank that has permeated. But I've seen a LOT of metal tanks that have literally turned into collanders. The welds are the weakest link, because they begin to oxidize immediately...but the first leak in aluminum tank is always just that--the FIRST leak. Sooner or later another one will develop...it just takes longer for the sheet metal to rust through. Pits start to develop within a year...how long it takes 'em to become holes depends on the thickness of the metal. Aluminum will fall apart a lot sooner than stainless, but I've never seen ANY metal tank last more than about 10 years...whereas good quality poly tanks last 20 years or longer. Although white vinegar does a great job of dissolving urine crystals and sea water calcium carbonates in the hoses and on the walls of the tank, it doesn't neutralize the corrosive properties in urine. Even if it did, "treating" the tank with it after only every 6-8 pumpouts accomplishes nothing. You'd have to completely flush ALL the waste out of the tank--rinse it thoroughly with clean water (salt or fresh, doesn't matter)--every time you pump out, and never allow any waste to sit in the tank longer than the boat is out, for it to do any good at all. Waste contains animal fats, which clog sending units and build up on the sides of the tank. They're what turns the tank brown inside...it's stain, not permeation. Vinegar won't do a thing for that, but a periodic dose of low suds detergent--because detergent emulfies oils and fats--left to sit in a tank full of water after pumpout helps keep the walls of the tank cleaner. Never use bleach, though...it's almost as corrosive as urine, damaging to hoses, rubber and neoprene, and environmentally UNfriendly. At least a nominal rinse with only clean water after EVERY pumpout not only reduces sludge, but also helps to keep any tank cleaner. I have no axe to grind whatever by recommending one tank material over another, or a particular manufacturer...I no longer sell anything, nor have any kind of relationship with any supplier. Nor is my advice and recommendations based solely on my own anecdotal experience with a few boats I've owned. It's based on solid research from knowledgable professionals--more of 'em outside the marine industry than in it--and more than 15 years of experience with literally hundreds of yards, boat owners, surveyors and boat builders. A good quality THICK-walled poly tank is the only material to use for waste holding.
You're right that cheap thin-walled tanks made from low grade low density poly will permeate...although they usually fail before that happens. The walls aren't strong enough support the weight of the contents, they bulge, flex and ultimately crack...usually in a few years. But often what is believed to be a permeated tank is actually leaking at fitting...just not quite enough to allow any liquid to escape, only gasses. 'Cuz when a tank bulges, the walls stretch pulling female fitting ports out of round. Bulging and stretching also thins the tank material, and the thinner the material, the faster it permeates. Good quality thick-walled tanks will also permeate--eventually. However, it takes decades, not just years, for permeation to make it all the way through the tank. Better quality poly, medium density instead of low, better curing and quality control are partly the reason, but also because the walls are strong enough to support the weight of the contents, there is no bulging or stretching...no weakening of the tank. In the more than 15 years that I sold tanks--and the 3 years since I sold my company, but still am asked to locate and solve odor problems--I've yet to see a good quality, thick walled poly tank that has permeated. But I've seen a LOT of metal tanks that have literally turned into collanders. The welds are the weakest link, because they begin to oxidize immediately...but the first leak in aluminum tank is always just that--the FIRST leak. Sooner or later another one will develop...it just takes longer for the sheet metal to rust through. Pits start to develop within a year...how long it takes 'em to become holes depends on the thickness of the metal. Aluminum will fall apart a lot sooner than stainless, but I've never seen ANY metal tank last more than about 10 years...whereas good quality poly tanks last 20 years or longer. Although white vinegar does a great job of dissolving urine crystals and sea water calcium carbonates in the hoses and on the walls of the tank, it doesn't neutralize the corrosive properties in urine. Even if it did, "treating" the tank with it after only every 6-8 pumpouts accomplishes nothing. You'd have to completely flush ALL the waste out of the tank--rinse it thoroughly with clean water (salt or fresh, doesn't matter)--every time you pump out, and never allow any waste to sit in the tank longer than the boat is out, for it to do any good at all. Waste contains animal fats, which clog sending units and build up on the sides of the tank. They're what turns the tank brown inside...it's stain, not permeation. Vinegar won't do a thing for that, but a periodic dose of low suds detergent--because detergent emulfies oils and fats--left to sit in a tank full of water after pumpout helps keep the walls of the tank cleaner. Never use bleach, though...it's almost as corrosive as urine, damaging to hoses, rubber and neoprene, and environmentally UNfriendly. At least a nominal rinse with only clean water after EVERY pumpout not only reduces sludge, but also helps to keep any tank cleaner. I have no axe to grind whatever by recommending one tank material over another, or a particular manufacturer...I no longer sell anything, nor have any kind of relationship with any supplier. Nor is my advice and recommendations based solely on my own anecdotal experience with a few boats I've owned. It's based on solid research from knowledgable professionals--more of 'em outside the marine industry than in it--and more than 15 years of experience with literally hundreds of yards, boat owners, surveyors and boat builders. A good quality THICK-walled poly tank is the only material to use for waste holding.
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Randy S.
Thx, and conclusions
Thx Peggy. I've decided to go with poly. I located a local manufacturer that makes custom tanks - I need custom to maximize the volume in the place it is going. He makes them out of 7/16 high density poly (UHMW I believe) and like you, assures me that for all practical purposes, it will NEVER leak or smell. They build all the holding tanks for the several yacht and super yacht builders in town. This installation will be immediately followed with the installation of a vacu-flush system for the primary head. That will certainly ease the volume issues with the slightly smaller sized tank I'll be going with. Regarding aeration, similar problem. The vent line is going to have to be approx 8-10' long. I will likely go 1", but a question: I'm considering using 2 vent lines, with a small (1-2") computer muffin fan permanently plumbed and wired in to exhaust from one of the lines. With the lines being routed from each end of the tank, this would assure constant air flow, and as per your writings, prevent the anaerobic environment that creates odour. In addition, I plan regular treatment with aerobic bacteria additive. Is this major overkill? I don't mind minor overkill, erring on the side of caution is greatly preferrable to stinkage. Thx....Randy
Thx Peggy. I've decided to go with poly. I located a local manufacturer that makes custom tanks - I need custom to maximize the volume in the place it is going. He makes them out of 7/16 high density poly (UHMW I believe) and like you, assures me that for all practical purposes, it will NEVER leak or smell. They build all the holding tanks for the several yacht and super yacht builders in town. This installation will be immediately followed with the installation of a vacu-flush system for the primary head. That will certainly ease the volume issues with the slightly smaller sized tank I'll be going with. Regarding aeration, similar problem. The vent line is going to have to be approx 8-10' long. I will likely go 1", but a question: I'm considering using 2 vent lines, with a small (1-2") computer muffin fan permanently plumbed and wired in to exhaust from one of the lines. With the lines being routed from each end of the tank, this would assure constant air flow, and as per your writings, prevent the anaerobic environment that creates odour. In addition, I plan regular treatment with aerobic bacteria additive. Is this major overkill? I don't mind minor overkill, erring on the side of caution is greatly preferrable to stinkage. Thx....Randy
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Peggie Hall/Head Mistress
Whether you need 2 vents and a fan depends
on how long the vent line(s) are, how straight, and how much vertical rise is required. If a single 1" line can be short--3' or less, straight and relatively horizontal, that should be enough. We still have the issue of a 20' run from your head to to the tank...If you're trying to connect two toilets at opposite ends of the boat to the same tank, it'll give you nothing but problems...and neither hard pipe nor a VacuFlush toilet will solve the problems that creates. The MAX distance between the V/Flush bowl and the vacuum pump is 15'--and that's only if the run is a straight shot. Every turn and corner impede the flow and reduces that distance considerably. When waste sits in the discharge hose/pipe, permeation isn't the only problem...the potential for a clog increases. The pump can push it another 6'--but again, that's the max for an absolutely straight shot, so any elbows or bends reduce that....and the V/Flush does NOT macerate. Nor does it offer ANY advantages--neither flush water consumption nor power consumption--over fresh water flush model macerating toilets...it just costs 3x as much. (And btw, I'm intimately acquainted with VacuFlush...not only were we a dealer for nearly 10 years, but I had one on my last two boats.) Looking at your location, I'd give serious to thought to putting a Lectra/San (CG Certified Type I treatment device) on the primary toilet and a holding tank only on the other one, to use only when you're in a "no discharge" harbor. For about half the price of a custom tank and VacuFlush, you can have the best macerating electric toilet on the planet--the Raritan Atlantes, which has a one piece houshold size china bowl and pedestal, fresh water flush that offers 4 touch pad flush options, but only needs a max of couple of quarts and can even do a "dry" flush, and uses only about half AH the V/Flush uses--AND the Lectra/San. The only other thing that makes sense is to find another location for the tank that's closer to the toilet. If you ARE trying to connect two heads the same tank, you should be able to go with smaller tanks on both, actually increasing your total capacity. Btw...if you'd like to send me an e-mail, I'll send you a couple of files you may find interesting. My e-mail address is in the owner directory
on how long the vent line(s) are, how straight, and how much vertical rise is required. If a single 1" line can be short--3' or less, straight and relatively horizontal, that should be enough. We still have the issue of a 20' run from your head to to the tank...If you're trying to connect two toilets at opposite ends of the boat to the same tank, it'll give you nothing but problems...and neither hard pipe nor a VacuFlush toilet will solve the problems that creates. The MAX distance between the V/Flush bowl and the vacuum pump is 15'--and that's only if the run is a straight shot. Every turn and corner impede the flow and reduces that distance considerably. When waste sits in the discharge hose/pipe, permeation isn't the only problem...the potential for a clog increases. The pump can push it another 6'--but again, that's the max for an absolutely straight shot, so any elbows or bends reduce that....and the V/Flush does NOT macerate. Nor does it offer ANY advantages--neither flush water consumption nor power consumption--over fresh water flush model macerating toilets...it just costs 3x as much. (And btw, I'm intimately acquainted with VacuFlush...not only were we a dealer for nearly 10 years, but I had one on my last two boats.) Looking at your location, I'd give serious to thought to putting a Lectra/San (CG Certified Type I treatment device) on the primary toilet and a holding tank only on the other one, to use only when you're in a "no discharge" harbor. For about half the price of a custom tank and VacuFlush, you can have the best macerating electric toilet on the planet--the Raritan Atlantes, which has a one piece houshold size china bowl and pedestal, fresh water flush that offers 4 touch pad flush options, but only needs a max of couple of quarts and can even do a "dry" flush, and uses only about half AH the V/Flush uses--AND the Lectra/San. The only other thing that makes sense is to find another location for the tank that's closer to the toilet. If you ARE trying to connect two heads the same tank, you should be able to go with smaller tanks on both, actually increasing your total capacity. Btw...if you'd like to send me an e-mail, I'll send you a couple of files you may find interesting. My e-mail address is in the owner directory
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Randy S.
More info
Thx again Peggy. As I said, the vent line(s) will be 8-10 ft. long, so I think I'll plan on pumping air (no big deal. The actual head line would measure out at 17 ft. There will be both heads connected, but that is not the design point, just a pleasant by-product. The issue is there no acceptable place closer to the aft head for a holding tank. Of the few possible locations, none are viable for several reasons: size, accessibility etc. All things in a boat are a compromise, right? I queried SeaLand re distance and turns, and was assured that 20' with the 2 turns I require would be no problem. Do you have some other info that suggests that 15' is the max? We already have a LectraSan - it will be replaced in this project. A great product, and your suggestion would be good for a cruising boat, but this is for a liveaboard situation. The VacuFlush claims 1 pint per flush. This sounds a little like some optimistic marketing claim, but even if I double that (to a quart per flush), it's still 1/3 that of the 3 quart rated flush of the Atlantis (which I don't have room for anyway). Fresh water consumption is critical. Also, with an electric or other head, you need to flush long enough to clear the discharge line, which at 1.5" and 17' is 1.56 US gallons (yeah yeah I know, that wouldn't be such a problem if the line wasn't 17' long). It is my understanding that one of the major benefits of the VacuFlush is the clearing of the line through the use of vacuum. As far as masceration, it is again my understanding that the velocity of the intial flush (the "burst" of vacuum) provides *some* breakup action. I wouldn't imagine as good as the ol' grinder, but still acceptable. Again, you sound as if you have some information that is contrary to my underdstanding. I do realize that the 'brochures' don't tell the whole story, and you have a fair bit of actual experience with the product, so I'd appreciate hearing the "hands-on" story. The one bright spot is the vac gen to holding tank distance - under 2'. One last question: for the tank discharge, take it off the bottom, or from the top with a dip tube? Pros and cons again: in the first case, minimal chance of blockage problems, but then you have residual goop in the discharge line as the tank fills. The second case minimizes the exposure to effluent sitting in the tank discharge pipe, but you can't empty the tank as completely, plus the risk of blockage around the bottom of the dip tube. Thx again....Randy
Thx again Peggy. As I said, the vent line(s) will be 8-10 ft. long, so I think I'll plan on pumping air (no big deal. The actual head line would measure out at 17 ft. There will be both heads connected, but that is not the design point, just a pleasant by-product. The issue is there no acceptable place closer to the aft head for a holding tank. Of the few possible locations, none are viable for several reasons: size, accessibility etc. All things in a boat are a compromise, right? I queried SeaLand re distance and turns, and was assured that 20' with the 2 turns I require would be no problem. Do you have some other info that suggests that 15' is the max? We already have a LectraSan - it will be replaced in this project. A great product, and your suggestion would be good for a cruising boat, but this is for a liveaboard situation. The VacuFlush claims 1 pint per flush. This sounds a little like some optimistic marketing claim, but even if I double that (to a quart per flush), it's still 1/3 that of the 3 quart rated flush of the Atlantis (which I don't have room for anyway). Fresh water consumption is critical. Also, with an electric or other head, you need to flush long enough to clear the discharge line, which at 1.5" and 17' is 1.56 US gallons (yeah yeah I know, that wouldn't be such a problem if the line wasn't 17' long). It is my understanding that one of the major benefits of the VacuFlush is the clearing of the line through the use of vacuum. As far as masceration, it is again my understanding that the velocity of the intial flush (the "burst" of vacuum) provides *some* breakup action. I wouldn't imagine as good as the ol' grinder, but still acceptable. Again, you sound as if you have some information that is contrary to my underdstanding. I do realize that the 'brochures' don't tell the whole story, and you have a fair bit of actual experience with the product, so I'd appreciate hearing the "hands-on" story. The one bright spot is the vac gen to holding tank distance - under 2'. One last question: for the tank discharge, take it off the bottom, or from the top with a dip tube? Pros and cons again: in the first case, minimal chance of blockage problems, but then you have residual goop in the discharge line as the tank fills. The second case minimizes the exposure to effluent sitting in the tank discharge pipe, but you can't empty the tank as completely, plus the risk of blockage around the bottom of the dip tube. Thx again....Randy
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