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Repairing leak in plastic rainwater tank

 
pollinator
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So, today I noticed a smallish leak in the vertical seam of my 1000 gallon rainwater tank. The hole isn't large, but it's about 6-9 inches from the bottom and the pressure is causes it to spray. I have emptied the tank and have looked online and am finding a lot of conflicting advice. Everything from remelting the seam, to drill a larger area and using a mastic. Has anyone made a repair like this or have any input or advice. These tanks are expensive and I don't want to have to replace it. Thanks in advance.
 
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Without have a great deal of specifics, I would go with epoxy.
 
pollinator
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I can't for the life of me remember the name of the stuff, but there is a type of tape that touts itself for use in just your situation.  I've seen commercials for it on my wife's facebook feed.  I imagine that as long as the surface was completely dry that Grace Ice and water shield tape or the tape that "zip" construction panels would work too.
 
pollinator
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Gosh, you may not be in the right place if you don't want conflicting advice!

I would try a patch of similar plastic secured with suitable epoxy, applied from the inside, substantially larger than the crack... but hopefully someone who has actually done this will come along!
 
pollinator
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Is it a split along the mould seam?

How old is it?

May well be covered by warranty.
 
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Make sure the epoxy is designed for boats, that is, it's flexible. Ordinary epoxy is hard and brittle, but the stuff for boats is designed to be underwater all the time.
http://www.totalboat.com/product/flexepox-flexible-epoxy-adhesive/
 
Stacy Witscher
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Thanks everyone for the replies. The tank was here when we bought the property, so I have no idea where or when it was purchased. It isn't possible to get inside the tank. I'm willing to try epoxy because it's less likely than some of the other ideas I've come across to further damage the tank and doesn't require special equipment. My father came across a couple of sites recommending using a tire plug in combination with the epoxy. That sounds promising. I haven't tried anything yet, as I'm not leaving the property currently. But I will keep everyone informed if I do something that works.
 
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I have repaired these tanks.
Can you send a photo please?
 
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There is a high likelihood that is high-density polyethylene and you cannot glue it... try putting a sticker on it if it doesn't stick real good glue isn't going to stick good including epoxy

HDPE can be welded though cut a piece of it near the top that you can afford to lose like a small welding rod and glue it in with a soldering iron after cleaning thoroughly with sandpaper to get off oxidation that will hinder the welding

Good luck enjoy
 
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Some years ago I helped a friend repair some bullet holes in his 500 gallon blue plastic water storage tank. We had to cut a round 24" hole in the top so that we could get inside. Once inside we smoothed the 1/4" bullet holes flat with a rasp and sandpaper. We then cut some 3/4" round pieces from a Tupperware bowl and taped them in place over the holes with Gorilla Tape. As far as I know they are still holding with no leaks. The hardest part was making a tight fitting cap to cover the 24" access hole.
 
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Try to find out what kind of plastic the tank is made of. You will probably need to just make a best guess, but do your best. The type of plastic matters because different materials do NOT respond to the same adhesives the same way.

Cutting access in the top and getting inside may be your choice of last resort - don't dismiss it out of hand.

Use a GOOD light and a magnifying glass (unless you have super-vision...) and try to determine for sure the extent of the leak. Bummer to make a repair and see it spray out 3" above that...  OR...   It _may_ be possible to pressurize the tank  - maximum of 5 PSI or _less_ (that's what is used for testing vehicle gas tanks, as I recall) - and use a "soap" (dish detergent) mix to find where all your problems are. Double check, read up on using air pressure to test this type of tank. Don't do it w/out getting 1st, 2nd, 3rd _knowledgeable_ input on what is safe. It may be as low as 1 or 2 PSI. The fact that water pressure at the bottom of the tank is greater does _not_ mean that you can use higher air pressure. But if you can find good info, it may turn out to be a way to actually test the damage and then your work before you spend time putting away your tools and filling the tank again.

John's offer to lend his knowledge is an extremely good one for you.


Regards,
Rufus
 
Stacy Witscher
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After looking up various types of tanks on the internet, I would agree that it's likely polyethylene. I tried taking a picture of it, but nothing shows up. Honestly, you can't really see it even in person until water is spurting out of it. The hole is small and on the vertical seam. Unfortunately, it's also on the side of the tank that faces a chain link fence, so I don't have good access.

I'm claustrophobic and would rather buy a new tank than climb inside. I don't have welding equipment or any welding experience, so if that's the best course of action, it would be something that I would hire someone to do.
 
Rufus Laggren
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> against ... a fence

Cutting the fence may be something you want to consider, stacked against the cost of replacement.

Nobody (well, relatively speaking) has plastic welding experience. Doesn't use the same equipment - "just" a super hair dryer that makes 600F. or so. You will need to search hard to find somebody plausible. If you go there, I would start with auto body shops - they deal with a lot of plastic these days and many have a guy who "welds" plastic. You will need at least 20amps of house power at the site and that may mean you need to get a pretty expensive power extension cord.

You _must_ get proper access to the exterior or it's all just a fun BS session. When you do, you can just try stuff that comes to hand. Gorilla tape (I'm betting a few days before failure), polyurethane adhesives from the box stores (the $10+ per cartridge kind). Getting weird, you could mound up a "hill" of polyurethane over the whole area, let it dry a week or so to get pretty solid, then lay a piece of 18ga sheet metal over that area and wrap a few lonnngggggg webbing straps around the whole tank (the type sold at the box stores to hold material on top of cars and trucks) and crank down on your patch to make a "positive attachment" as the code books say... <GG> You want good firm pressure over the whole area so the sheet metal, curved a bit around the tank, is important.

Best luck.


Rufus
 
John C Daley
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If the tank is empty you may be able to move it around for access to repair
 
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Stacy, what you could do is install a valve there.  Mark the spot first before you lower the water level.  If it's a 1" leak, get a 1 1/2" or 2" valve that screws into a tank fitting (like the black plastic one below, not a metal fitting)  that fits through the wall in a drilled hole the size of the male threaded part of the fitting that will go to the inside of the tank.  There's probably already a tank fitting on it where the valve is that you can see as an example.   Even if you can't get inside, you run a string or rope in through the new bottom opening in the tank, keeping a foot or so outside of the tank, either held by someone or taped to the exterior of the tank.   Catch the rope or string with a tool of some sort and pull it up through the top opening of the tank.  So you've now got a straight line from the top of the tank to the new opening.

Someone on a ladder puts the washer on the rope at the top, and put the male part of the fitting through the hole at the bottom, with the string sticking out the fitting (before you screw the valve into it.)   Let the washer slide down the tight rope to the male projecting piece that is inside the tank, and carefully make it land on the male threaded end and pull tight on the rope, taping the rope at the top with duct tape, to the top of the tank,  if there's only one person, while the person on the outside sticks their finger through the fitting and lines up the washer with the male threads, hold it with a finger while screwing it tightly from the outside.  That will seat the fitting to the tank wall through the new hole.  Then when that is nice and tight, screw in the valve, making sure it is closed, and refill the tank.  

A valve and a fitting might cost about $10 or so.

It might take a day or so for the new fitting to be wet and expand to a tight seal.  

Tank fitting:

TankFittin.jpg
[Thumbnail for TankFittin.jpg]
 
D Nikolls
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Cristo Balete wrote:Stacy, what you could do is install a valve there.  Mark the spot first before you lower the water level.  If it's a 1" leak, get a 1 1/2" or 2" valve that screws into a tank fitting (like the black plastic one below, not a metal fitting)  that fits through the wall in a drilled hole the size of the male threaded part of the fitting that will go to the inside of the tank.  There's probably already a tank fitting on it where the valve is that you can see as an example.   Even if you can't get inside, you run a string or rope in through the new bottom opening in the tank, keeping a foot or so outside of the tank, either held by someone or taped to the exterior of the tank.   Catch the rope or string with a tool of some sort and pull it up through the top opening of the tank.  So you've now got a straight line from the top of the tank to the new opening.

Someone on a ladder puts the washer on the rope at the top, and put the male part of the fitting through the hole at the bottom, with the string sticking out the fitting (before you screw the valve into it.)   Let the washer slide down the tight rope to the male projecting piece that is inside the tank, and carefully make it land on the male threaded end and pull tight on the rope, taping the rope at the top with duct tape, to the top of the tank,  if there's only one person, while the person on the outside sticks their finger through the fitting and lines up the washer with the male threads, hold it with a finger while screwing it tightly from the outside.  That will seat the fitting to the tank wall through the new hole.  Then when that is nice and tight, screw in the valve, making sure it is closed, and refill the tank.  

A valve and a fitting might cost about $10 or so.

It might take a day or so for the new fitting to be wet and expand to a tight seal.  

Tank fitting:



I can see this working really great on a puncture on a flat surface!

I am a bit sceptical of this approach on the side of a round tank.. have you used them on a curved surface?

I am *very* sceptical of this applied to a crack-type leak at a failed seam!

 
Cristo Balete
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Yes, I have four of these polyethene tanks, ranging from 300 gallons to 2400 gallons.  They all have that kind of "plastic" fitting (not sure what it's made of, but it's not metal), some of them have two of them.  The curve is not that extreme even on the 300-gallon tank.  They do say not to put a heavy valve and fitting there, and create some kind of support with an upright PVC post that holds up the line so there is as little weight as possible pulling down on the fitting.

If the seam really is failing, there's no point in saturating the soil underneath the tank in waiting for that to happen.  That could destablize the ground it's on, causing the tank to sink on one side and destablizing the weight load in it, causing a seam to fail.  Too much water in the soil can destabilize a hillside it's on, and that's a bad thing if it's uphill from a house or buildings and saturating the ground near or under the buildings.  

Stopping that leak will show if it was one spot that was weak or had even been hit by something.  If another part of the seam goes, then you have your answer, but it could be years before that happens, and using the tank until then at least keeps it out of a landfill.  If leak is high on the tank, then an overflow line can be installed just below the leak so the tank only fills to the point of the leak.  
 
pollinator
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yeah i was totally thinking you might use it as an opportunity to make a new line coming out, install a valve.

if it is super tiny i might try to seal it with fire. do this at your own risk though. well sometimes i melt nylon threads and ropes, so this is something i do. i have the hang of doing it with my craftwork, to finish off an end. you have to be very careful, obviously. its not that hot even if you touch it, but i can easily ruin something if i use too much flame with a lighter, or the wrong angle to seal the end (and also get any flyaway bits of string if the string frays).

i would seriously just see if i could remelt in that spot by putting a small torch/one of those really big lighters to it, carefully quickly...and then maybe more intensely if quickly didnt work to melt it together. i might even try to stick something small in there, like the nylon cord i sometimes work with .
 
Stacy Witscher
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As we are entering our dry period, I'm putting off dealing with this. Right now, I have a hose draining the tank directly into raised beds. I can move the hose after each rain storm, we are not getting much rain this year and nothing is saturated, so it's still helpful. The tank is below my house on the hillside, so no worries about that.
 
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you need flex tape!!!

it works!!!

https://www.youtube.com/watch?v=0xzN6FM5x_E


 
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