Fresh water Tank Repair

[Agent4573]

The threads on the drain of my white water tank were destroyed before I bought the RV. I would like to have a new fitting "spin welded" into the tank. I've called about 6 different rv repair shops around orlando today and not a single one knew what I was talking about. They all said they could rig something up with epoxy and tape, but thats just asking for it to fail at the worst time. Does anyone know where I can go in florida that can properly fix a white water tank? Would I be better off just spending the 250 dollars to buy a router and drive adapter and doing it myself? If I can't find anyone to fix it, is there a site that sells a 1998 dodge pleasure way white water tank?

[GeorgeRa]

I would research manufacturers of chemical tanks for chemical processes in Florida, you could have better luck than with RV folks not understanding your point.

If you decide to do it yourself a 2HP router should for example this one - https://www.harborfreight.com/2-hp-f...ter-68341.html , should be good enough for the job, but, trying a few prototypes before the final weld would help you.

Spin welding is good but you can also weld a fitting in with a simple plastic welder, also from Harbor Freight like this one - https://www.harborfreight.com/plasti...ure-96464.html Learning curve could be less steep.

[CaDreamin]

Just an offhand thought but I wonder if a machine shop could help you. Drill out a larger hole and then cut threads for a larger fitting.

Also if you remove the tank and install a deck plate on the top surface then you would be able to put your hand in there and install a through fitting. That would hold indefinitely.

I wouldn’t hold out much hope for glue. Almost nothing sticks to that type of plastic.

It’s fairly easy to weld though. Shops that do repairs on plastic kayaks are often very adept at plastic welding.

[Mexray]

Ditto on any glue sticking to poly tanks... tried a special kit just for that from Tap Plastics didn’t work either...

I then went to West Marine & got a ‘thru-hull’ fitting & an access cover... I installed the cover in the top of the tank so it was then easy to get access & drill out the cracked outlet & install the threaded thru-hull fitting... West Marine also has Siliflex Marine sealant that will insure no more leaks at these connections-also good stuff for roof sealant...

[JPMcG]

Spin welding might work and not leak. If your not successful here is a good last resort.

West Marine type thru-hull fitting. Mount that fitting in a 6" dia. plastic or aluminum disk.
Hole saw the plastic tank about 2"dia. (stick a bung in the hole to start your hole saw drill) Mount the 6" disc with Dow 5200 and a few ss self taping screws.
Good luck.

[<<B-Guy>>]

Originally Posted by GeorgeRa

I would research manufacturers of chemical tanks for chemical processes in Florida, you could have better luck than with RV folks not understanding your point.

If you decide to do it yourself a 2HP router should for example this one - https://www.harborfreight.com/2-hp-f...ter-68341.html , should be good enough for the job, but, trying a few prototypes before the final weld would help you.

Spin welding is good but you can also weld a fitting in with a simple plastic welder, also from Harbor Freight like this one - https://www.harborfreight.com/plasti...ure-96464.html Learning curve could be less steep.

George,

Just curious - have you ever tried the Harbor Freight plastic welder? Reason I ask is that I bought one some years ago and try as I might never had much luck in
making a decent weld with it!

I did play around with the temp control and air volume quite a bit but never did really get the hang of it - it is still in irs box out in the garage - nobody would take it off my hands at our last garage sale even at knock down price!

I do have a stick welder and mig welder that I can use reasonably well so thought I should have no trouble with this unit - didn't turn out that way. Luckily I didn't buy it for any serious job I had to do so all I did was practice on scraps of plastic!

Probably just my lack of skill, maybe if I had stuck with it! I've had better luck welding broken plastic items with a soldering iron!

Brian.

[D&J Phillips]

Originally Posted by Wingeezer

George,

Probably just my lack of skill, maybe if I had stuck with it! I've had better luck welding broken plastic items with a soldering iron!

Brian.

About 35 years ago a shop I was working in needed to weld various plastics and we quickly found it depended greatly on the type/grade of plastic material.

HDPE (polyethylene) is easy to weld, just using air, melt and add filler like you might when oxy welding steel. We had pretty good results.

PVC on the other hand was quite difficult. We found air was not best and we used Nitrogen to reduce oxidation at the weld. Beyond that, it took lots of practice because there is a fine line between melting enough to weld and burning the base material - we got lots of fairly nice looking welds that had no real strength. We found it very difficult to achieve penetration without burning the material so you had to "V" the weld area and make several filler passes to slowly fill the V. I'd guess average penetration in the thousandths rather than tenths of an inch

Again, this was about 35 years ago and things should have evolved some by now, but I ended up having very little faith in hot air plastic welding.

Dave

[<<B-Guy>>]

Originally Posted by D&J Phillips

About 35 years ago a shop I was working in needed to weld various plastics and we quickly found it depended greatly on the type/grade of plastic material.

HDPE (polyethylene) is easy to weld, just using air, melt and add filler like you might when oxy welding steel. We had pretty good results.

PVC on the other hand was quite difficult. We found air was not best and we used Nitrogen to reduce oxidation at the weld. Beyond that, it took lots of practice because there is a fine line between melting enough to weld and burning the base material - we got lots of fairly nice looking welds that had no real strength. We found it very difficult to achieve penetration without burning the material so you had to "V" the weld area and make several filler passes to slowly fill the V. I'd guess average penetration in the thousandths rather than tenths of an inch

Again, this was about 35 years ago and things should have evolved some by now, but I ended up having very little faith in hot air plastic welding.

Dave

Dave,

Perhaps I might have had more luck if I spent more time with different compositions of plastic. Most of my experiments were with an old garden plastic garbage can that was cracked pretty much beyond any hope of repair. I just cut it up with tin snips and cut myself some strips of filler material to see what I could do - mostly, f I could bring things to a melting point I just woudn up blowing holes in it an messing with heat settings and air volumes didn't improve my results!

Brian.

[avanti]

Originally Posted by D&J Phillips

PVC on the other hand was quite difficult.

Wouldn't one chemically weld PVC?

[D&J Phillips]

Originally Posted by avanti

Wouldn't one chemically weld PVC?

Normally, yes, if pipe or other lap joints.

We were in the pre-insulated piping system business and in most cases customers would spec their desired materials - for some of our jobs there was a spec for PVC outer jacketing so when we had fittings like wyes or tees they had to be insulated with stub-outs of the inner pipe extending beyond the insulation and outer jacket so they could be assembled in the field and a standard 'joint kit' could be installed over the pipe connection.

So, in order to make up the fittings, we would weld short lengths of pipe onto the fitting to extend beyond where the insulation would end and then we assembled the outer jacket and welded the jacket and then we filled the void with urethane foam insulation. Since we had to miter cut PVC pipe for the outer jacket that left us with a butt weld because there was no good way to overlap for 'cement'. Once the urethane foam was applied the fitting became a very stable, solid piece, but the outer jacked had to be watertight, and if you had urethane leaking out when you foamed it, you knew you weren't water tight.....
Miserable job

[GeorgeRa]

Originally Posted by Wingeezer

George,

Just curious - have you ever tried the Harbor Freight plastic welder? Reason I ask is that I bought one some years ago and try as I might never had much luck in
making a decent weld with it!

I did play around with the temp control and air volume quite a bit but never did really get the hang of it - it is still in irs box out in the garage - nobody would take it off my hands at our last garage sale even at knock down price!

I do have a stick welder and mig welder that I can use reasonably well so thought I should have no trouble with this unit - didn't turn out that way. Luckily I didn't buy it for any serious job I had to do so all I did was practice on scraps of plastic!

Probably just my lack of skill, maybe if I had stuck with it! I've had better luck welding broken plastic items with a soldering iron!

Brian.

I did a few small jobs on ¼” HDPE sheets I used in my conversion, results were OK, key was constant speed and material match. My expertise is not at the level of professional know how. But I have seen some beautiful double fillet welds on very large tanks, leaks were rare or none existent.

[JohnnyFry]

JPMcG: I believe that 5200 is a 3M product, not DOW. I agree that it is a very tenacious adhesive which will stick to neatly anything. I have not tried it on Polyethylene however.

[<<B-Guy>>]

This product has a specific claim to work well with polyethylene - I have never tried it though and so am still a little skeptical, but Loctite is a well known and respected company so could be worth an experiment!

https://www.homedepot.com/p/Loctite-...1925/100371829

Brian