Tip # 36, from da Lone Ranger: On how to ruin your water tanks.......

Submitted: Wednesday, May 11, 2005 at 02:49
ThreadID: 121964 Views:3244 Replies:2 FollowUps:2
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You cannot pressure fill these light poly tanks. There have been suggestions about making up a tight fitting assembly to pressure fill your tanks faster…. This will ruin the tanks. The vent (on top of each tank) is smaller than the hose you can push down inside the filler neck, and if you seal it off to push in the water at a faster rate, the tank swells as the air cannot be expelled fast enough through the smaller vent on the top of the tank. This swelling eventually causes the tank to fail, even if you turn it off as soon as the first sign of water coming out the vent. It could work if the fill rate was slow enough, but at a high volume/rate, it stresses the tank. Air will compress a bit and blow out the smaller vent on top of each tank, if the rate is not too fast…. But water in this practical sense does not compress… As the tank fills up, and water starts to spurt out the top tank vent, the tank swelling will exponentially increase rapidly, as the vent on top is smaller than the filler hose.. This is also the case if you have too large and tight fitting hose jammed into the filler neck, and the water spurts violently back at you, same situation, and you are grossly shortening the life of your tanks… And getting wet…

We see them split at seams, fittings strip, all kinds of failures as a result of this. Now, the best way, is to use something like a piece of the grey hot water plastic flexible pipe that your HWS in plumbed in. It has an (I.D.) of about 3/8” and outside (O.D.) is still a little less than ½ inch. It is stiff enough to find the hole in the filler easily, and I just put snap fittings on it… But it also just slips up inside most hoses with a reasonably snug fit… And the most important thing is that when the tank is full and the vent on top of the tank is spilling water steady, it still will not spit the water back at you out of the filler. It just overflows and runs out gently onto the ground as there is plenty of clearance. This means you are not pressurising the tank, and so are not stressing it to failure on the first or tenth or hundredth time you fill the tanks… But trust me, it happens.

Better to have the vent on top of the tank overflowing onto the ground and the filler overflowing gently onto the ground when you are distracted by something and leave it running full… So, don’t use too large of a piece of hose to block off the small opening in the Filler! You want it to run out when full and you need to open another tank, not spurt out violently as that is too tight of a fit! As to one well meaning suggestion about putting a taper of tape on the hose to jamb it down the filler hole and seal it so you can pressure fill it at a high rate…. Three things: No, No, and furthermore No!…. It will blow the tank eventually… Maybe not the first or tenth time, but it will happen. We have a large stack of them out back from just that. I hate to throw away the carcasses so we save them for ……? Oil change pans, liners for …. Anyway, we have a stack of them from doing just that…

Cheers from the “Lone Ranger”, out on the Frontier…
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Reply By: Bushtracker - Wednesday, May 11, 2005 at 14:06

Wednesday, May 11, 2005 at 14:06
Post Script:
By the way, to all Bushtracker Friends, if you stop in for any other reason, I am happy to give you a piece of that stiff grey hose if you like....

We used to put it in the vans, sometimes forget, anyway......

If you stop by for any reason, just ask, I am all too happy to help..

Cheers from "da Ranger"....
AnswerID: 566321

Reply By: Richo - Wednesday, May 11, 2005 at 15:35

Wednesday, May 11, 2005 at 15:35
All of the the methods discussed here, now and in the past are all great and all have dangers and limitations, they do however address the fixing of the symptom not the problem.

The problem is as mentioned, is the breather on the tank. Mine is approx 6mm diameter. Put simply this limits the maximum flow rate of the water to that equal to using a 6mm hose to fill the tank, that is, without creating pressure in the tank and filling system.

The fix. Improve the the breather system to allow the use of the 12mm filler capacity.

Over to you Mr Bushtracker.


Peter Richardson
AnswerID: 566322

Follow Up By: Bushtracker - Wednesday, May 11, 2005 at 18:35

Wednesday, May 11, 2005 at 18:35
Great Idea Peter!!
And I mean that, good lateral thinking.... I really do appreciate outside ideas, as there are probably 500 "Contributing Engineers" over the last ten years.... So keep them coming.... But in this case, as is often the case, we who have been doing this in the thousands of times crossed this barrier many years ago. While in theory this is the answer: Just increase the exhaust! There were some serious problems we could not easily overcome….

1) We had trouble sealing a larger pipe into the tank. The existing one barely fits into the existing fitting depression where there are two tiny breather holes now. We could not get a larger hose in there, and still have the flexibility to route it while retaining the stiffness we need to keep it rigid for this application.... We cannot have any movement in it, or it sags in the heat and chafes with movement, as water lays in a loop in it.. It really is the best size, to fit in the existing threaded orifice that has a couple of holes drilled in it for the vent location…. If we put a plug in that vent recess, there is no other practical locations to hook up to….

2) There are no other tanks that are practical affordable that fit, without loss of volume or ten times the cost with custom tanks…

3) We cannot put in a fitting into that spot and run a larger line out because the tanks are taller than the full width of the chassis rails now, even going up 50mm further to the floor. The layout of the floor cross members even has to fit the tanks to get them up high enough now without an added fitting… And we need the cast in threads of that fitting for enough mechanical adhesion to seal the vent pipe. In this case larger is not better…

4) The purpose of the loop in the line is to keep out bulldust, with a water trap. As it is, the end of the line gets some of dust in it, that gets blown out each time it is filled. Larger lines seemed to plug up more, and added another dimension to the problem.. Actually smaller would be better for this application..

Anyways, keep the ideas coming!!! We are always trying to do it better, that is why we are where we are. But many times the obvious is obscured by some other complication buried inside. Sometimes one solution causes other problems bigger yet... But keep on thinking and coming up with suggestions OK?

Kind regards, stg at Bushtracker
FollowupID: 844554

Follow Up By: Bushtracker - Thursday, May 12, 2005 at 16:22

Thursday, May 12, 2005 at 16:22
Hello again Peter,
Just an after thought, there was one more problem we discovered when playing with the idea of custom tanks and such... Which I still toy with
as we could do some interesting shapes and volumes with the white seam welded rigid tanks.... But anyway, the larger vent meant a loss of water as we bounced around through rutted out tracks. The surging water actually squirted some fairly large spurts of water, resulting in a large loss of the top quarter or third of the tank of water in time...

I am still playing with the white heavy wall seam welded tank concept, even thinking about them for diesel... But that is another topic..

Regards, Bushtracker
FollowupID: 844555

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