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Old 04-03-2021, 05:08 PM   #61
Montana Man
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Agree with all that. In the example of a fuel tank, they are engineered to a high level. But none the less they are made to hold together. A first year engineering student could have designed a way to make our tanks hold up. Or, they could have simply followed the tank manufacturers guidance. I don't want to harp on this subject but what they did frys me. They saved probably $50 and we are cutting out and replacing the nastiest parts of our $60k+ trailers.
 
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Old 04-03-2021, 06:28 PM   #62
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First I had to replace grey tank because flange around discharge port cracked. Then overdilled black tank, hears it burp, and separated from the lid. After I installed black tank, I added support straps. They are made from perforated plumbers strap covered by 4 layers of shrink tube. Strapping is bolted to basement floor with carriage bolts.

I solved the fill to rinse problem with water flow meter (under $20). I know exactly how much water I've put in.

https://www.amazon.com/Rainwave-RW-9...s%2C288&sr=8-3
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Old 04-04-2021, 08:56 AM   #63
azwiz
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Originally Posted by Montana Man View Post
Agree with all that. In the example of a fuel tank, they are engineered to a high level. But none the less they are made to hold together. A first year engineering student could have designed a way to make our tanks hold up. Or, they could have simply followed the tank manufacturers guidance. I don't want to harp on this subject but what they did frys me. They saved probably $50 and we are cutting out and replacing the nastiest parts of our $60k+ trailers.
I bet they didn't save that much, probably $20.00 if that. Rv co's will cheapen stuff up for penny's!! Just to put bonus $ in ceo's pocket!
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Old 04-04-2021, 09:40 AM   #64
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Roto Moulded Tank Link

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Originally Posted by Montana Man View Post
This tank appears not to be roto molded. The ones I've seen have a tall flange around the perimeter. Not thin where the top and bottom sections of the tank are glued/bonded together. As in where yours split apart.

A rotomolded tank may require modifying the hangars by which the tanks rest. You'll know when you see one and how your trailer is built. The original two piece tank can still be satisfactory if supported on the bottom as well. Some members have posted pics of their fine work.
This is where I will be going when my tank fails.

https://www.plasticwatertanks.com
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Old 04-04-2021, 11:36 AM   #65
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So you're saying they're made better now?

Brad
Are you kidding me, nothing is made as good as before, only cheaper to boost profits!
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Old 04-04-2021, 01:32 PM   #66
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I had trouble ciphering this comment

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Originally Posted by Hblick48 View Post
First I had to replace grey tank because flange around discharge port cracked. Then overdilled black tank, hears it burp, and separated from the lid. After I installed black tank, I added support straps. They are made from perforated plumbers strap covered by 4 layers of shrink tube. Strapping is bolted to basement floor with carriage bolts.

I solved the fill to rinse problem with water flow meter (under $20). I know exactly how much water I've put in.

https://www.amazon.com/Rainwave-RW-9...s%2C288&sr=8-3

Did you mean to say black tank instead of gray tank? The picture provided was of the black tank. The "overdrilled tank", was that supposed to read "overfilled tank"? "Hears it burp" I'm guessing this is describing a noise that occurred during the overfilling???? Like any autopsy, an accurate description of the events in their proper order are important clues as to what caused a failure. If we are to learn from these failures, an accurate description needs to be presented. The original poster to this thread, described a failure which occurred during the flush process of the black tank. It included a confession that he lost track of time until he heard a "pop" accompanied by fluid leaking from the underbelly. While there may have been contributing factors in the original poster's black tank failure, such as tank brittleness from age, older 2 piece design which the OP has (see his photo), tank support design, we should all at least agree that flushing the black tank unsupervised with the dump valve closed, is rife with undesired consequences. Just don't do it!
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Old 04-04-2021, 01:49 PM   #67
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Concerning one piece roto molded tanks- while they are a vast improvement compared to 2 piece tanks of yore, they can and will change shape more akin to a ball than a rectangle, IF you do the same thing the original poster did, i.e. leave the valve closed and forget to shut off the garden hose, what Diesenguy in post # 26 said will happen, the floor above will lift, and or the support straps will bust. Just sayin.
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Old 04-04-2021, 01:49 PM   #68
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Originally Posted by firestation12 View Post
Did you mean to say black tank instead of gray tank? The picture provided was of the black tank. The "overdrilled tank", was that supposed to read "overfilled tank"? "Hears it burp" I'm guessing this is describing a noise that occurred during the overfilling????
Yes, I meant overfilling. Virtual keyboards aren't my favorite.

Tank burped when I flushed it, and it was it. Picture posted was grey tank. I also reinforced black tank like grey. Montana actually installed black tank under support...angle iron welded side to side onto frame located right under drain flange.
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Old 04-04-2021, 02:22 PM   #69
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Originally Posted by firestation12 View Post
Concerning one piece roto molded tanks- while they are a vast improvement compared to 2 piece tanks of yore, they can and will change shape more akin to a ball than a rectangle, IF you do the same thing the original poster did, i.e. leave the valve closed and forget to shut off the garden hose, what Diesenguy in post # 26 said will happen, the floor above will lift, and or the support straps will bust. Just sayin.
A properly mounted rotomolded tank won't rupture be merely filling it via the tank rinser. Water will find the next path(s) of resistance and flow there.
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Old 04-04-2021, 02:38 PM   #70
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Are you kidding me, nothing is made as good as before, only cheaper to boost profits!
I'll buy that statement in most cases. However back in the day when I was a teenager / young adult if you could get a car to a hundred thousand miles you did good and it was pretty well worn out.
Forward from the last decade-plus into today cars are made much better last way longer then they did back in the day. It's almost a given that any car can hit 200000 miles today with proper maintenance which is way simpler than it used to be.
Hell you don't even have to change plugs belts hoses antifreeze for at least the first hundred thousand miles. Front end alignments are almost non-existent or necessary
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Old 04-04-2021, 04:11 PM   #71
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On our previous 5th wheels, I'd fill the tank till the water crept up to the toilet and the drain the tank..did that on this one and the tank busted..
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Old 04-04-2021, 04:45 PM   #72
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On our previous 5th wheels, I'd fill the tank till the water crept up to the toilet and the drain the tank..did that on this one and the tank busted..
Exactly what I'm saying they do not like to be overfilled. It makes the top separate from the bottom. Empty them when they're no more than 3/4 full and you're more than likely won't have an issue. Knock on wood mines a 2011 unit never had a tank replaced or repaired.
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Old 04-04-2021, 06:56 PM   #73
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A properly mounted rotomolded tank won't rupture be merely filling it via the tank rinser. Water will find the next path(s) of resistance and flow there.

It appears a further explanation is in order to my quoted statement. I have no knowledge any tank roto molded or 2 piece, having survived rupturing, being subjected to NON STOP filling via the on board flush system with the dump valve closed. I would also like to know if someone out there has had an overfilled black tank to the point that effluent exited the roof without a tank failure. What I do know is the physics involved for that to happen. Montana Man seems to think that the vent pipe in the top of the black tank will prevent any pressure buildup. This is provably false as there are many stories that describe a tank rupturing after accidentally leaving the flush line running and the dump drain valve closed. The amount of pressure to be present in a black tank such that liquid can be pushed upwards to the top of the vent opening, is relatively small. A scant 4.34 psi is all that is required to do the job. So how can 4.34 psi cause a tank to fail??? Here's where physics comes in. Let's discuss the terms pressure and force. One of Boyle's Laws states that force is equal to pressure times area or F=P x A. A 35 gallon tank for example having a top dimension of 20"x40"= 800 Sq. inches. Using Boyle's law we see that 4.34 psi X 800 sq in = 3,472 of force pushing upward on the tank's top. The tank's bottom also will also be subjected the same force plus the weight of water it supports. So even if you've got the Home Improvement Binford 9000 roto molded tank and it is able to push liquid out the roof vent, I can guarantee that the Binford 9000 roto molded tank, will not be shaped like a suitcase anymore but rather more like a beach ball. As for the Superman support struts and the bullet proof floor above the black tank, something is going end up bad. If you are using a wand inserted into the toilet to flush your tank, the above warning does not apply. I'll leave it to the reader to figure out what happens when a wand type flusher is left unattended in the toilet.
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Old 04-04-2021, 07:33 PM   #74
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Firestation12, a plastic tank filled will experience deformity to some degree. Proper bracing will reduce deformity and prevent malfunction. As a past hydraulic mechanic, I understand the rationale you use to make your point even though Boyle's law generally applies to gasses. Pascale's law speaks to fluids in a confined space. The problem is there isn't enough resistance to the incoming fluid to reach the pressures in your example. If the tank were not vented then yes, the laws of hydraulics physics would apply in a much different manner.

Why is it that many of us fill the FW tank until it overflows and not rupture the tank? Because those tanks are not of the same design and/or mounting of the grey and black tanks. The waste tanks are buckling under their own weight. Not due to being pressureized to thousands of pounds.
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Old 04-04-2021, 08:12 PM   #75
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Duh, senior moment made me write Boyle in lieu of Pascale. Thanks for the correction. Your fresh water tank typically has an 1 1/2” corrugated tube over flow tube, that has no rise to it like the black tank vent. It also is a very short length. Neither is conducive to creating the back pressure the black tank does. As for lack of resistance to create the pressure, that is non sequiter. Close the black tank valve, climb up on top of the camper and place a garden hose end inside the waste vent opening. Turn the water on slowly, then come back the next day. Let’s see what happens. When I request a rough-in plumbing inspection, the inspector checks the 10’ water filled vent pipe to determine if the trenched in plumbing has no leaks. The 10’ of elevation produces 4.34 lbs of pressure at its base without the need of a pressurized water source. Filling your camper’s black tank via the vent pipe till water backs up and overflows, will prove my point nicely.
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Old 04-04-2021, 08:28 PM   #76
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The lack of resistance to the incoming force of water makes all the difference. Without back pressure, all that is happening by filling the vent pipe is adding another 4+ lbs of weight to a tank already holding 400+ lbs of static weight.

BTW, I've had plumbing tested in the example you gave. It pressurizes drain lines to a low pressure to test for leaks in a drain system not designed to be pressurized at all. That's how 4 lbs of pressure is all that's needed.
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