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Avoid ANY metal for sewage holding
Although you’ll see aluminum and stainless holding tanks, no metal of any kind should ever used to hold sewage. Urine is the most corrosive material it’s possible to put next to any metal. While the sheet metal walls of a metal holding tank may last up to a decade (rarely any longer once it’s actually put in use to hold sewage), metal tanks will typically begin to leak at a seam or a fitting in two to five years. You may be able to repair it, but the first leak is always just the first leak; the tank is gradually turning into a collander. Stainless will last a little longer than aluminum, but even the best 316 stainless holding tank rarely lasts more than 10 years. Rotationally molded seamless polyethylene with a minimum wall thickness of about 3/8” for the smallest tank is the only material that should be used for waste holding. If the wall thickness doesn’t continue to increase with size, the tank walls will be too weak to support the 8.333 pounds per gallon that sewage weighs (meaning a 40-gallon tank must support 333 pounds); it will bulge and, at the very least, distort and create leaks at the fittings--if it doesn’t actually crack. There are poly tanks being sold as holding tanks through most of the marine catalogs which have maximum 1/4” walls. People buy them because of price and out of ignorance. I strongly urge you to avoid them and spend the extra money to do it right the first time by installing a top quality tank that will last for decades. The above is an excerpt from my book (see link below) which also includes detailed instructions for installing a holding tank. Your best source for a top quality tank is Ronco Plastics...they make TOP quality thick-walled tanks for a very reasonable price and have more than 400 shapes and sizes, including over 100 non-rectangular...and they install fittings in the sizes and locations specified by the customer when they make the tank.
Although you’ll see aluminum and stainless holding tanks, no metal of any kind should ever used to hold sewage. Urine is the most corrosive material it’s possible to put next to any metal. While the sheet metal walls of a metal holding tank may last up to a decade (rarely any longer once it’s actually put in use to hold sewage), metal tanks will typically begin to leak at a seam or a fitting in two to five years. You may be able to repair it, but the first leak is always just the first leak; the tank is gradually turning into a collander. Stainless will last a little longer than aluminum, but even the best 316 stainless holding tank rarely lasts more than 10 years. Rotationally molded seamless polyethylene with a minimum wall thickness of about 3/8” for the smallest tank is the only material that should be used for waste holding. If the wall thickness doesn’t continue to increase with size, the tank walls will be too weak to support the 8.333 pounds per gallon that sewage weighs (meaning a 40-gallon tank must support 333 pounds); it will bulge and, at the very least, distort and create leaks at the fittings--if it doesn’t actually crack. There are poly tanks being sold as holding tanks through most of the marine catalogs which have maximum 1/4” walls. People buy them because of price and out of ignorance. I strongly urge you to avoid them and spend the extra money to do it right the first time by installing a top quality tank that will last for decades. The above is an excerpt from my book (see link below) which also includes detailed instructions for installing a holding tank. Your best source for a top quality tank is Ronco Plastics...they make TOP quality thick-walled tanks for a very reasonable price and have more than 400 shapes and sizes, including over 100 non-rectangular...and they install fittings in the sizes and locations specified by the customer when they make the tank.
part 2
Thanks, I've looked at Ronco and can't find tanks for the aplication. I'm working on an Endeavour 37CC and there is no room for the required holding tanks. I'm considering converting one of the water tanks in the saloon to the holding tank, that's why I asked. Pat
Thanks, I've looked at Ronco and can't find tanks for the aplication. I'm working on an Endeavour 37CC and there is no room for the required holding tanks. I'm considering converting one of the water tanks in the saloon to the holding tank, that's why I asked. Pat
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