My friends just finished a shakedown cruise on theur refinished 1958 Tyler Newell sloop. The tanks were brand new and after two days sailing up Long Island Sound the brand new stainless steel holding tank exploded as the captain was pumping the head. The tank buckled up about 6" damaging a setee and a seam split wide open. No injuries. What might have caused a new vented system to build up so much pressure? BTW there is no discharge from the tank, just a pumpout. The tank exploded as the head was being pumped with much resistance. My friends are on a cruise and asked me to relay their plight in the hope of some insight into the cause. Thanks Michael
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fred miller
Exploded Tank
I suspect you mean the tank "burst" as opposed to a true "explosion". My guess is that the vent system is fouled or simply totally insufficient in size. Pumping can put a lot of pressure on the tank, hoses and fittings. Check the venting . . Recently I heard of a tank exploding from a build up of methane gases while the owner working on the system and was smoking. That must be a very unsual occurence though. Fred Miller S/V M Squared
I suspect you mean the tank "burst" as opposed to a true "explosion". My guess is that the vent system is fouled or simply totally insufficient in size. Pumping can put a lot of pressure on the tank, hoses and fittings. Check the venting . . Recently I heard of a tank exploding from a build up of methane gases while the owner working on the system and was smoking. That must be a very unsual occurence though. Fred Miller S/V M Squared
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Peggie Hall/Head Mistress
Definitely a blocked tank vent
which is more common in new installations than you might think. In fact, it's even possible that the tank was never vented...THAT happens more often than you might think, too. That it blew while the head was being pumped "with much resistance" is the clue. If he was feeling that much resistance, WHY did he keep pumping??? That HAD to tell him something wasn't right. They'd been aboard for two days, using the toilet...and I'll BET that after the first couple of uses, the toilet began to get harder and harder to pump, but they just ignored it...till finally something had to give. That it was the stainless steel tank that gave is amazing--and also says it was either very flimsy stainless, a shoddy job of welding, or both...'cuz that much pressure should have either blown off a hose or erupted back up the toilet discharge with enough force to turn the joker valve inside out and give him a bath in waste. Moral: When you feel backpressure, STOP PUMPING! Send 'em the articles in the HM forum reference library (link on the forum homepage) so they can learn how to properly use and maintain a toilet and holding tank. And since they have to replace the tank anyway, tell 'em to put a good plastic tank in this time. They never should have used metal for waste holding in the first place, 'cuz if it hadn't blown, urine would have eaten through a weld in a couple of years anyway. Fred, till I got to "pumped with great resistance," my first thought was, methane and static electricity. CG regs require all holding tanks to be vented to the outside of the boat because methane is flammable...explosions in unvented bladders and rigid tanks with blocked vents are more common than you might think.
which is more common in new installations than you might think. In fact, it's even possible that the tank was never vented...THAT happens more often than you might think, too. That it blew while the head was being pumped "with much resistance" is the clue. If he was feeling that much resistance, WHY did he keep pumping??? That HAD to tell him something wasn't right. They'd been aboard for two days, using the toilet...and I'll BET that after the first couple of uses, the toilet began to get harder and harder to pump, but they just ignored it...till finally something had to give. That it was the stainless steel tank that gave is amazing--and also says it was either very flimsy stainless, a shoddy job of welding, or both...'cuz that much pressure should have either blown off a hose or erupted back up the toilet discharge with enough force to turn the joker valve inside out and give him a bath in waste. Moral: When you feel backpressure, STOP PUMPING! Send 'em the articles in the HM forum reference library (link on the forum homepage) so they can learn how to properly use and maintain a toilet and holding tank. And since they have to replace the tank anyway, tell 'em to put a good plastic tank in this time. They never should have used metal for waste holding in the first place, 'cuz if it hadn't blown, urine would have eaten through a weld in a couple of years anyway. Fred, till I got to "pumped with great resistance," my first thought was, methane and static electricity. CG regs require all holding tanks to be vented to the outside of the boat because methane is flammable...explosions in unvented bladders and rigid tanks with blocked vents are more common than you might think.
J
John Visser
I'll bet...
he said "Holy sh*t" when that happened! Really - how on earth do you blow up a stainless steel holding tank with a manual head pump??? Think about it! As an engineer, I'd recommend the following process for any yacht system: 1. Functional Requirement Specification 2. Alternatives and Feasibility Study 2a. Alternative Selection 3. Functional Spec. 4. Design Spec. 5. Implementation 6. Design Verification Testing 7. Deployment Testing Each process step is followed by a review. Your friends were on step 7 during their cruise. If there was no vent designed-in, this would have shown up somewhere pretty early in the process. If the vent was in the design, but not installed, this would have shown up after step 6, before "DVT." The tank would have had a specification, hopefully, and an inspection prior to installation might have caught thin walls or bad welds. Source qualification would help here (i.e., reputable manufacturers). How to address while cruising? Here's my recommendation: Alternative A: 1. unclog vent or punch vent into tank; 2. "weld" tank with mettalized epoxy putty (I carry a couple of "sticks" of this - get it at a big plumbing supply store for about $6/4 oz., or pay douple at True Value) 3. "Weld" a nylon or brass hose nipple into vent hole punched into tank - use 1/2" male pipe to 5/8" hose barb. 4. Use garden hose lashed to stanchion or mast for vent hose. Alternative B: 1. "Weld" tank. 2. Remove pump-out cap prior to pumping head. Hey, where are they now? If thy're near Westport (Massachusetts on hte Eastern end of Rhode Island Sound, almost due North of Cuttyhunk), call F.L. Tripp at 508-636-4058 or hail them on Ch. 9 and ask if they can fix it for them. They are great, good in-house skils, including welding (they build the Tripp Angler boats here), and pretty good stock of parts, good prices. jv
he said "Holy sh*t" when that happened! Really - how on earth do you blow up a stainless steel holding tank with a manual head pump??? Think about it! As an engineer, I'd recommend the following process for any yacht system: 1. Functional Requirement Specification 2. Alternatives and Feasibility Study 2a. Alternative Selection 3. Functional Spec. 4. Design Spec. 5. Implementation 6. Design Verification Testing 7. Deployment Testing Each process step is followed by a review. Your friends were on step 7 during their cruise. If there was no vent designed-in, this would have shown up somewhere pretty early in the process. If the vent was in the design, but not installed, this would have shown up after step 6, before "DVT." The tank would have had a specification, hopefully, and an inspection prior to installation might have caught thin walls or bad welds. Source qualification would help here (i.e., reputable manufacturers). How to address while cruising? Here's my recommendation: Alternative A: 1. unclog vent or punch vent into tank; 2. "weld" tank with mettalized epoxy putty (I carry a couple of "sticks" of this - get it at a big plumbing supply store for about $6/4 oz., or pay douple at True Value) 3. "Weld" a nylon or brass hose nipple into vent hole punched into tank - use 1/2" male pipe to 5/8" hose barb. 4. Use garden hose lashed to stanchion or mast for vent hose. Alternative B: 1. "Weld" tank. 2. Remove pump-out cap prior to pumping head. Hey, where are they now? If thy're near Westport (Massachusetts on hte Eastern end of Rhode Island Sound, almost due North of Cuttyhunk), call F.L. Tripp at 508-636-4058 or hail them on Ch. 9 and ask if they can fix it for them. They are great, good in-house skils, including welding (they build the Tripp Angler boats here), and pretty good stock of parts, good prices. jv
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Peggie Hall/Head Mistress
All good points, John
The welds HAD to be exceptionally weak to split the tank before it could erupt through the toilet. If the tank had been sound, the path of least resistance in the system would have been back up the head discharge line, turning the toilet into a geyser when the pressure reached "critical mass." It's happened to more than one person. Mike, did your friend fabricate and install the tank himself?
The welds HAD to be exceptionally weak to split the tank before it could erupt through the toilet. If the tank had been sound, the path of least resistance in the system would have been back up the head discharge line, turning the toilet into a geyser when the pressure reached "critical mass." It's happened to more than one person. Mike, did your friend fabricate and install the tank himself?
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