Plastic Repair

[Wingnut]

Yesterday was a good day all around ... not only did I toast the pressure washer, but I also got stopped halfway through spraying cleanser on the house first. I have a sprayer unit from Black & Decker that has a 3 gal plastic tank (on a rolling frame) and a Versa battery unit to pressurize it.
Anyway, halfway through ... just as I'd dumped another gallon of cleaner in the tank and was repressuring, I noticed that I'd sprung a leak. Don't know it it was stress or a manufacturing defect, but there's a crack on the bottom. Since I've had it 2 years (although only used it several hours at most) it's long out of warranty and I'd always rather fix than replace.
Anyone tried "plastic welding" yet? If so, is it strong enough to withstand pressure? Is there a better way to attempt a repair? (I was thinking maybe epoxy from inside?)
Hope I don't have too many more days like that .... $400 pressure washer and $100 sprayer becoming toast in one afternoon ....

 

[Ozarker]

I have never tried to mend a place where there is pressure but I use that two part glue called Plastic Welder from Devcon and it is fantastic stuff. I have used it to repair my grandsons toys and if he breaks it a second time, it is never where I used that Plastic Welder.

When I repair someplace that will have stress, I cut a small splint out of an aluminum drink can and embed that in the repair.

 

[Gary_in_Indiana]

Have you considered some type of bladder/liner for it?

 

[chim]

The AgriFab 15 gallon tow-behind sprayer developed a leak after I stressed the plastic by jacknifing it behind the tractor last year. The tank has what appear to be nuts embedded in the plastic to accept mounting screws that go through the tube frame. I was doing a little "chemical mowing" and managed to kill a 2" wide by several hundred foot strip of grass before noticing the leak. Oops.

The fix was smearing gobs of Goop - real name - on the inside of the tank. Fortunately the tank has a big screw-on cap near the center that allows reaching the whole inside if necessary.

This stuff is seen in hardware stores, supply houses and the 'Marts. I've seen different versions of Household Goop, Plumber's Goop, etc. I think I used Plumber's Goop. I reassembled the tank and frame, and used it a couple of times on its own wheels. This Spring I had the guys in one of our fab shops whip up a small 3PH platform to strap it onto. This is a much better setup since it doesn't trail on wheels - handy for backing in places and maneuvering.............chim

 

[Bird]

Wingnut, I have no experience with plastic welding; haven't even seen it done, but when my brother was running the tool truck, he sold a plastic welding machine of some kind to a body shop and told me the guy that bought it could do miraculous things with it. You might try calling body shops in your area to see if have such equipment.

 

[Wingnut]

Thanks guys,

Gary, not sure about a bladder ... but I'll try that if nothing else works ... that's one idea I hadn't considered.

Ozarker and Chim, my first thought had been some sort of patching material ... first I thought of epoxy but I remember using goop one time ... the problem will be getting it down there ... kind of hated the "pour it down to the bottom and twist the container to spread" method that would be required since the opening isn't large enough for my hand (and arm).

Bird, that welding was what I was thinking about ... just wondering whether our "brain trust" had tried it on stressed or pressurized tanks yet. Back when I was Alberta, the Grain News weekly that I subscribed to had a series of articles by a guy who did all kinds of plastic welding .... Harbour Freight even sells a cheap kit now for about $35. I just didn't want to try something that would make it worse instead of better.

I guess try # 1 will be whatever Goop promises it's chemically resistant.

 

[Ozarker]

You couldn't pour that Plastic Welder stuff in and spread it by twisting the tank around. It isn't fluid enough. You would have to remove the tank and repair from the outside.

 

[Kodiak]

You might try the rubberizes roof coating paint that they sell for motor home and travel trailer roofs. Sno Seal is one brand that comes to mind.

 

[Chuck52]

Does the tank have a screw top? I wonder if it might be a standard container. Nalgene makes various sized plastic carboys. They sell mainly to labs and lab supply companies. Might not be too expensive to simply replace the tank.

Chuck

 

[centex]

I have used an old wood burning pen as well as soldering irons and scrap plastic to weld plastic in the past with good results. I have used things like Bic ball point pens as filler but for a clear plastic tank I would try to find something similar to use a filler. I am not sure this type of plastic will take the heat without burning though. It is always best to practice on similar scrap material - maybe an old piece of tupperware.

 

[Wingnut]

Unfortunately, Chuck .... this is a formed plastic container with lots of nifty tabs for connecting the wheel/holder frame. I think I'll take tomorrow off and try the goop on this and the wrench on the motor ....

 

[Scott_in_WVA]

I buy this at the hardware store,I do not know if it would be of help...but it is good stuff.<A target="_blank" HREF=http://www.jbweld.co.uk/>http://www.jbweld.co.uk/</A>
would you be better served to get a new plastic tank maybe?
There is an outfit near me that is a distributor of plastic tanks and plastic valves/fittings etc...they are pretty big and that is all they deal in.

 

[BOOMERANG]

Wingnut,
As a follow on to Scott's comments, I use JBWELD to fix just about everything from plastic to metal. I was skeptical at first when I saw a neighbor fix a cracked head on his boat motor with it. I thought it would never hold but it did. I even filled in a dime sized hole in the oil pan of my El Camino and it hasn't leaked since! You should try it !

 

[Wil]

I've used JB Weld on automobile radiators ( not sure what pressure they develop) and plastic parts both, it has never failed me.

 

[Scott_in_WVA]

It is definately tough stuff and very handy to have around the home.

 

[bellweather]

Don't know what your tank looks like, but repairs to any plastic container that gets pressurized are difficult, especially if you dont have access to the inside. You might try contacting the manufacturer directly and see if they will sell you a replacement part...assuming it is possible to disassemble the unit.

 

[Wingnut]

OK ... OK .... I'll try it ... I'll try it!
/w3tcompact/icons/smile.gif
I have used JB Weld on gas tanks and it has performed flawlessly .... I'll try it first and, if that doesn't work, we'll go with the Goop. If THAT doesn't work ... I will finally try my hand at plastic welding (since I'll have nothing to lose, right?) .... and then final resort is to contact good ole Black and Decker and see whether they still sell this sprayer (it's 2 years old and has 2-3 hours of use on it). Knowing what their spares cost ... that'll be the last choice.
I don't think I can get my big hands into the tank to spread JB Weld or Goop .... but my wife's petite hands should fit handily ... make her feel useful too. I really don't want to try and pour anything down there as it'll get into the intake and clog it ... and then it is replacement time.
This was one of those "hey, neat" purchases .... when B&D was going nuts with their Versa stuff. But it does work real well. All it really does is the same as the pump-type sprayers ... except that it "pumps itself".
There's been so much interest oin this thread (I was hoping I'd get one or two responses .... you guys got WAY too much time on your hands /w3tcompact/icons/grin.gif), I'll post a pic when I have a few free minutes (at home, instead of here at work).
Thanks again, all!

 

[Ozarker]

You may not be able to get your hand in there but I'll bet you can get a stick in there. Maybe a tomato stake with the end cut to a knife edge like a narrow putty knife?

 

[patrickg]

Wingnut, some plastics can be welded and some just don't work too good, breaking down from even the lowest heat required to weld. I have had some amazing successes welding plastic and some dismal failures too.

I didn't get a clear idea of the shape of the damaged area but am assuming there is no missing material just a small crack or puncture. I have had success pulling a little vacuum on a plastic container and getting repair material to be sucked up through the crack. You don't have to reach inside with your hand or a tool. You can even enlarge the crack with a gently applied wedge or drilled hole(s) to permit sucking in thicker materials.

Sometimes it is good to drill a "crack stopper" hole at each end of a crack to reduce the stress concentrating effect of the sharp radius of curvature of the sharp "end" of the crack. These holes will be filled with repair material anyway and help the situtation not weaken it.

You can suck in enough repair material to cover the entire area around the leak (plus a little extra) then put, (dare I say it?), duct tape over the repair area on the outside, then while positioning the vessel such that the leak is the lowest point, relieve the vacuum and add enough pressure to force some of the repair material back out through the leak forming a slight buldge under the duct tape. If you use a two part (catalyzed) repair material just put down the tank with the patch at lowest point and wait for a good cure. If you use something like GE Silicone Seal leave the lid off the tank to admit atmospheric moisture (required for curring RTV-Silicone Seal that emits acedic acid (smells like vinegar) when curring. If you have real low relative humidity, wet a paper towl and place in the tank to provide a higher relative humidity (in this case you can put the lid on the tank).

The vacuum idea works pretty good but don't get too carried away and collapse the container. Brake bleeder vacuum pumps are one source of vacuum. A vacuum hose from a car intake manifold or carb is another. There are gizmos that are powered by a garden hose that are used to suck up water (venturi effect, see Bernoulli's principle) a flat piece of wood with a hole for a piece of tubing can be your temporary "lid" for doing the vacuum trick.

Best of luck to you,

Patrick

 

[Wingnut]

Excellent tips, Patrick ... which reinforce what I have planned to do .... the crack looks like it is either a manufacturing flaw (weak point) or an impact crack .... might have got kicked / hit when the wifie was moving it around on one of her cleaning expeditions. Anyway, I was planning on a small hole at each end of the crack to stop it from spreading and then using pressure from inside to force the bonding material (jb weld first try) out. Vacuum will work as well (or better ... that way I can leave it open to work on it). The duct tape was also in my plans .... having ridden a motorcycle for 20 years and various ATV's even longer ... I don't leave home without it. Duct Tape and mechanics wire have replaced baling wire and chewing gum as the fix du jour!