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Old 05-01-2022, 10:44 AM   #1
Phil Eyler
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All tanks leak

i don't think I've ever seen this problem before. I have a 2014 3402RL and all my tanks , black and gray, are two piece tanks. the top is actually like a lid that is glued on. All of my tanks leak where the top is glued on. i have to make sure that i empty my tanks before they get full or yuk. The gray tanks don't bother me that much. If they overflow it's just gray water, but I really need to watch the black tank because that can be very unpleasant. I've tried repairing the seam where the leak is but to no avail. i can either live with this or I could have the black tank replaced. That can be pretty expensive if I could even find someone to do it. Has anyone else had this problem? my feelings are that the person who glued the tops on the tanks did a poor job the day they made my unit. Other than that we really love our Montana.
 
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Old 05-01-2022, 12:05 PM   #2
Carl n Susan
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Montana has used two piece tanks for many, many years. They just recently moved to single piece Roto-Mold tanks but that won't help you.

The two piece tanks with the glued top are notorious for breaking the seal due to overfilling the tank or even driving down the road with a full, or almost full, tank. There was an excellent discussion here about the effect of hydraulic pressure from the contents and how little it takes to bust the top loose. A Search may find it.

As you have found, repairing the loose top is problematical. The best solution is to replace the tank. And apparently, tanks have been affected by the current shortages (I have no idea why) and they take about 9 weeks to get one (according to my friend who is awaiting his).
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Old 05-02-2022, 07:25 AM   #3
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Also, if you replace the tanks it really helps to have supports added underneath the tanks. If anyone has the skills to change the tank they could easily fabricate a support.
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Old 05-02-2022, 08:55 AM   #4
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I had a black tank that was leaking....J B Weld fixed it. They have several versions, get the one of the ones for PVC/plastic/fiberglass, called "J B Weld, PlasticWeld." Be sure the area to be patched is clean and dry.
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Old 05-02-2022, 08:14 PM   #5
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We have had both gray and black tanks spring a leak and the dealer has tried to repair them. They even sent them out to a company that plastic welds and they repaired the tanks to no avail. Once that two-piece tank comes apart, you can reseal it but EVENTUALLY the thing will do the same thing. I had a gray tank replaced last fall before heading for our snowbird landing and while returning home and sitting for a week at a location we heard a loud back the had water coming out of the belly. The new gray tank had blown and the problem was that there was only two showers of water in the tank. You see even the NEW tanks will blow their top even with two showers in them. Oh, by the way the tanks are well supported now since each tank has been replaced over the 9 years of use. We keep track of showers taken for the gray tank and empty the shower gray every four showers to be on the safe side. Apparently, even that is not a safe thing to do anymore.
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Old 05-03-2022, 04:01 AM   #6
Mikendebbie
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What year did they change from the two-piece tanks to the molded tanks?
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Old 05-03-2022, 07:12 AM   #7
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Originally Posted by Mikendebbie View Post
What year did they change from the two-piece tanks to the molded tanks?
I don't know but ours is a 2016 built in 2015 and has rotomolded tanks. I know of a 2015 that has two piece tanks.
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Old 05-03-2022, 07:47 AM   #8
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2015 was the changeover year around March. We had rotomolded tanks in our 2015 3160 delivered in April.
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Old 05-08-2022, 02:26 PM   #9
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Originally Posted by Rondo View Post
We have had both gray and black tanks spring a leak and the dealer has tried to repair them. They even sent them out to a company that plastic welds and they repaired the tanks to no avail. Once that two-piece tank comes apart, you can reseal it but EVENTUALLY the thing will do the same thing. I had a gray tank replaced last fall before heading for our snowbird landing and while returning home and sitting for a week at a location we heard a loud back the had water coming out of the belly. The new gray tank had blown and the problem was that there was only two showers of water in the tank. You see even the NEW tanks will blow their top even with two showers in them. Oh, by the way the tanks are well supported now since each tank has been replaced over the 9 years of use. We keep track of showers taken for the gray tank and empty the shower gray every four showers to be on the safe side. Apparently, even that is not a safe thing to do anymore.
You have something else going on, no amount of showers should blow a tank, First thing is why is it closed, it's grey not black. Second is no pressure can build up if the venting is working. Try taking a hose to the roof and start filling the vent. Observe the clear elbow for flow out the appropriate grey drain. If water comes out of the vent on the roof, then the vent is blocked. WARNING the guy who installed the new tank may not have installed a vent, the tank is sealed so water doen the vent will come out somewhere in the belly, you may want to put water in really slowly and drop the coroplast ro observe.
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Old 05-08-2022, 04:33 PM   #10
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<snip>......Second is no pressure can build up if the venting is working.....</snip>
Not Exactly. Member Firestation12 posted, over two years ago, the following explanation of how there is pressure applied to the top of the tank when it is overfilled.

"A hydraulic law every aspiring fire truck driver is taught: One pound of pressure will push a column of water (in a pipe) 2.3 feet high or to put it conversely, a column of water 2.3 feet high, exerts a pressure of 1 psi at it's base. With this knowledge, let's look at the problem posted i.e. the tank ruptured. Assuming a height of the tank's vent pipe opening being 10', the following applies: 10' divided by 2.3 equates to 4.348 psi at the top of the tank when the water exits the vent opening. Using a tank dimension of 24" X 48", the total square inches of the tank top is 1,152. Then if the 4.348 psi is multiplied times the square inches of the tank's top, we see that the total force applied is 5,008.896 pounds. At the point the tanks becomes full and the water is just at the point of entering the vent pipe, the tank pressure climbs from zero to 5,008 in just the short time it takes to fill the interior of the 1 1/2" vent pipe (maybe 5 seconds?). Lesson to be learned here is stay far, far away from over filling the tank. Another post by DQDICK suggested the possibility of a blocked vent pipe. Imagine if this scenario were to occur: the tank psi would be whatever the pressure of the source water supply. Thus 40 psi house pressure times the 1,152 square inches would equal 46,080 pounds of force on the tank top. "
Source: https://www.montanaowners.com/forums...ad.php?t=80123 Post #12
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Old 05-08-2022, 04:40 PM   #11
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Originally Posted by Carl n Susan View Post
Not Exactly. Member Firestation12 posted, over two years ago, the following explanation of how there is pressure applied to the top of the tank when it is overfilled.

"A hydraulic law every aspiring fire truck driver is taught: One pound of pressure will push a column of water (in a pipe) 2.3 feet high or to put it conversely, a column of water 2.3 feet high, exerts a pressure of 1 psi at it's base. With this knowledge, let's look at the problem posted i.e. the tank ruptured. Assuming a height of the tank's vent pipe opening being 10', the following applies: 10' divided by 2.3 equates to 4.348 psi at the top of the tank when the water exits the vent opening. Using a tank dimension of 24" X 48", the total square inches of the tank top is 1,152. Then if the 4.348 psi is multiplied times the square inches of the tank's top, we see that the total force applied is 5,008.896 pounds. At the point the tanks becomes full and the water is just at the point of entering the vent pipe, the tank pressure climbs from zero to 5,008 in just the short time it takes to fill the interior of the 1 1/2" vent pipe (maybe 5 seconds?). Lesson to be learned here is stay far, far away from over filling the tank. Another post by DQDICK suggested the possibility of a blocked vent pipe. Imagine if this scenario were to occur: the tank psi would be whatever the pressure of the source water supply. Thus 40 psi house pressure times the 1,152 square inches would equal 46,080 pounds of force on the tank top. "
Source: https://www.montanaowners.com/forums...ad.php?t=80123 Post #12
Different scenario. I am suggesting the vent is not connected to the tank at all, they didn't drill the hole for it so the tank is sealed, but if it is and they overfill it then your scenario might also account for a blown tank. Either way it's a big problem.
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Old 05-08-2022, 04:58 PM   #12
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Ron from up North-- I have been leaving my gray tank closed from the beginning when we started camping in our first Montana over 18 years ago. It will explode and I can guarantee you that! I've had two do it and there is nothing wrong with the venting of the tanks. I've checked them all and no problems. It was my fault on the first gray tank rupture because I let it get too full and the tank blew its top. This tank was a NEW tank but it came to the dealer with a thin spot on the curve of the upper lip and before they installed it they filled it to make sure there were no leaks. Well guess what, the tank got full and the thin spot blew out. The dealer sent it to a plastic welding shop and supposedly fixed it but it was not even full when it blew out this time. I didn't take the coroplast down but it did blow and I felt it while in the shower and the wife heard it all the way down in the living room. The company that made the two piece tanks for Keystone is not doing it anymore so they have to find someone to replace them and the company that is doing it is not doing a good job, period. The dealer got three identical tanks in and all three had that same thin spot or hole. It's to bad that we can't find someone to figure out how to mold a one piece tank for those of us that have the older model Montana's. If found, that company would make a fortune making replacement tanks for us.
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Old 05-08-2022, 05:09 PM   #13
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I hear what Carl is saying and it makes sense to a point. But, when our grey tank gets full it will back up in the shower before going all the way up the vent pipe since water seeks it's own level. Same with the galley tank. And for that matter it would stand to reason the if the black tank is full, before it goes all the way up the vent it seems it would not flush down the toilet.

Or is there something here I'm not seeing? In all the tanks there is actually two points of pressure relief, the vent and the drains leading into the tanks.
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Old 05-08-2022, 09:44 PM   #14
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Originally Posted by DebNJim B View Post
I hear what Carl is saying and it makes sense to a point. But, when our grey tank gets full it will back up in the shower before going all the way up the vent pipe since water seeks it's own level. Same with the galley tank. And for that matter it would stand to reason the if the black tank is full, before it goes all the way up the vent it seems it would not flush down the toilet.

Or is there something here I'm not seeing? In all the tanks there is actually two points of pressure relief, the vent and the drains leading into the tanks.
That's right. These tanks are not exploding from thousands of pounds of pressure. There is a big difference between adding pressure in a closed system vs. adding 7 pounds in an open system. The two piece tanks usually deform under the weight of water to the point of failure. I've watched it happen. If the rails that the tank hangs from don't hug the tank closely, the weakening is compounded. Two piece tanks should have support from below to make them reliable.

Keystone installed two piece tanks against the recommendation of the tank manufacturer. I got that from the manufacturer of the tank.
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Old 05-09-2022, 04:04 AM   #15
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Exploding tank

Actually, that calculation is incorrect. You don't multiply to get 5000 #'s pressure. You should divide and get less total pressure.
Think of a snowshoe. A man weighs say 160 lbs. and his shoe has a sole of say 24 sq-in. He steps out in a foot of snow and sinks to the ground. Now he puts on snowshoes and has a sole of around 240 sq-in and now only sinks in about and inch. His total weight is spread out over a larger area. If we got 5000# of pressure at the top of a tank, they would all be exploding whether they were one piece or two.
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Old 05-09-2022, 10:08 AM   #16
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I had to replace both the black and gray tank in my '04 because of cracks where the lid was glued on. The dealer I ordered the tanks from told me never to travel with a substantial amount of liquid in those tanks. Those tank edges cannot take the pressure bouncing down the highway.

When I replaced them, I did put a strap under each tank to help support the weight until I can dump them.

I always travel with about 4 gallons of water in the black tank, added after I dump for obvious reasons.
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