rick83864
Sandpoint, ID
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danr1707 wrote:So the black tank has a vent? Maybe is was clogged with leaves? I've overflowed my gray tank and that just backed up into the shower. It didn't "explode".
All 3 of my RV's had a plumbing vent just like your house. They have all had a extended cap to prevent leaves and such clogging them. They even sell the wind driven devices at CW to help vent the odor. I think over filling the black tank with the santi-flush would only over flow the tank resulting in the liquid coming up to the toilet then maybe putting enough pressure to pop the tank. I would think a full tank of sewage would weigh more than H2O.
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RCMAN46
NorthWest
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laknox wrote:Jim&Peg wrote:Possibly they were backflushing the tank to rinse it. If you overfill the tank with a flusher it is possible to burst the tank. These large flat tanks will not withstand any pressure. The tank often bursts before the water rises to the top of the vent. There is at least one or two posts of that happening every year. Sometimes it even bulges and ruins the floor above the tank.
I'm still trying to get my head around a tank bursting with a 2" column of liquid less than 10' high providing pressure on it. A water-column barometer holds what, about 35' at 1 atmosphere pressure (i.e. 30" of mercury)? Is there a back-flow valve in the vent that prevents liquid from rising in the vent pipe but allows gas outflow? I just don't understand how this could "explode" from pressure in the tank unless it's a closed system and you're getting 40-60 psi from the hose. Makes much more sense if a seam weakened and let loose while the tank was near-full. 
Lyle
At 10 ft the pressure would be about 4 1/4 psi. PapPappy has indicated these tanks are only good for about 3 psi. May be enough to cause a problem. Plus a 5/8 hose at 40-50 psi may be able to input water faster than a 2 inch vent could expel without additional pressure build up.
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sheldons65
Fort Worth, TX
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I believe instead of lime it would be better to get some of the septic system bugs you can buy, mix with warm water and pour or spray over the area. You want something to digest and break down that material.
One of the of the drain build up removers would work as well....same basic stuff....bacteria. Not all bugs are bad.
Lime is an immediate solution to smell but not long term.
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laknox
Arizona
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danr1707 wrote:So the black tank has a vent? Maybe is was clogged with leaves? I've overflowed my gray tank and that just backed up into the shower. It didn't "explode".
Has to have a vent or it wouldn't drain without the commode being open. Were the vent clogged when the tank was drained, it would =implode= from the vacuum produced. Ask any farmer that irrigates and uses gravity-dispensed water-run chemicals what happens to the nurse tank if the vent is plugged. If you left your rinse hose on and the black tank filled you'd have a) a backflow in the commode (unlikely since it's supposed to seal pretty tightly), or b) (much more likely) a black fountain off the roof.
Lyle
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laknox
Arizona
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Here's a Redneck experimental solution... First, find an old fiver or TT with a black tank and commode that are still tight and relatively clean, and tow it into a convenient field next to a willing neighbor's house. Next, get a few buddies over, each with a cooler of beer and crank up some Merle. Drink a beer. Get a ping pong ball, or something that will float in the vent tube and about 15 feet of stiff but light wire. JB Weld the wire to the ping pong ball and drop it down the vent. Drink a beer, or two. Attach the garden hose to the tank flush valve and drink more beer while lounging in your folding chair while the tank fills. Change the CD to Hank, Jr. You can have the AA guy on the roof measuring the wire. See if it fills up or blows up. Drink the rest of the beer. Call the DW's to come pick you up...if you dare. :-) Please be sure to post pics...or mug shots; either is fine.
Lyle
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ryoung
Indiana
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If as previously stated, that black tanks are rated around 3 psi, why then would a vent system be designed that could cause the tank to rupture by liquid filling the vent pipe?
Vent pipes not only allow gases and air to escape, but also allow any liquid overfill to escape, preventing the tank from rupturing.
The thought that liquid filling up to the top of the vent pipe will cause the tank to rupture is hogwash. I think the tanks are designed for more than 3 psi.
ryoung
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racinghoss
Maryland, but missing AK
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So you guys have backflush valves built on to your drain pipes? I dont. I use an aftermarket elbow joint (got it at WalMart) to backflush. I have to leave the drain valve open, or the water does not get up the tube into the tank.
I will start with the elbow pointing at the ground and backflush until the water is clear (the elbow joint is clear), then I will change the elbow to point right and repeat, then point up and repeat, then left and repeat. It is the only way I can get all the junk out. There is no danger of pressure building up this way.
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mr. ed
Madison, SD (currently traveling the US)
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Deleted post...not relevant.
Mr. Ed (fulltiming since 1987)
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smkettner
Southern California
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ryoung wrote:If as previously stated, that black tanks are rated around 3 psi, why then would a vent system be designed that could cause the tank to rupture by liquid filling the vent pipe?
Vent pipes not only allow gases and air to escape, but also allow any liquid overfill to escape, preventing the tank from rupturing.
The thought that liquid filling up to the top of the vent pipe will cause the tank to rupture is hogwash. I think the tanks are designed for more than 3 psi.
ryoung
It is a gas vent to prevent gas pressure from building up. If you just use the can for your business, you will need dump before anything liquid goes up out the top. The design is solid. Then people use these pressure washers (myself included) that the original design does not allow for and it can bust. My turbo flush says to only operate with the drain valve open.
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john b
anywhere USA!
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laknox wrote:Jim&Peg wrote:Possibly they were backflushing the tank to rinse it. If you overfill the tank with a flusher it is possible to burst the tank. These large flat tanks will not withstand any pressure. The tank often bursts before the water rises to the top of the vent. There is at least one or two posts of that happening every year. Sometimes it even bulges and ruins the floor above the tank.
I'm still trying to get my head around a tank bursting with a 2" column of liquid less than 10' high providing pressure on it. A water-column barometer holds what, about 35' at 1 atmosphere pressure (i.e. 30" of mercury)? Is there a back-flow valve in the vent that prevents liquid from rising in the vent pipe but allows gas outflow? I just don't understand how this could "explode" from pressure in the tank unless it's a closed system and you're getting 40-60 psi from the hose. Makes much more sense if a seam weakened and let loose while the tank was near-full.
I totally agree with Lyle when you have a 2 in vent & a max 3/4 in feed line of water it makes no sense that it should cause a tank to blow up! I know of another Montana that had a tank open up and it was warranted because of manufacturing shortfall! I run both of my tank rinsers at once and stay to watch but never a problem 6 years later.MUO jb
Lyle
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