polyethylene tanks repair

[foster]

I found this that could be useful : in DIY boat owner:</

b>
Easy Repair for Leaking Poly Tanks 1/53/03 Print E-mail or Username
By Jan Mundy

We thought it was impossible to repair a leaking polyethylene water tank until a DIY reader asked for help and our research lead us to Kracor, a manufacturer of such tanks. The company provided the following procedures to repair small cracks and holes in poly tanks.

You'll need a heat gun or propane torch, drill and 1.5mm (1/16") bit, strips of a polyethylene container or polyethylene welding rod and small metal putty knife or similar tool. It sounds easy, so if you give it a try let us know the outcome.

Another product that has successfully "welded" poly tanks is 3M Scotch-Weld Structural Plastic Adhesive DP-8005, a two-part adhesive that bonds StarBoard, as tested in DIY 2000-#4 issue. Cost for a glue applicator and cartridges is about US$150, which is a bargain considering the cost (and work involved) of a new tank. For specs, ontact the 3M Helpline at 1-800-3M-Helps. Follow these steps to repair poly tanks with polyethene strips or rods.

Step 1: Thoroughly clean the surface of the tank in the area to be welded. Be sure the area is completely free of grease, oil and any silicone-based lubricants.

Step 2: For small cracks, use a 1.5mm (1/16") drill bit and drill one hole all the way through on each side of the crack in order to prevent the crack from radiating.

Step 3: Preheat a wide area around the area to be welded. A heat gun is best used for this process as it heats a wider area and provides good control over heat application. If using a propane torch, be careful not to overheat and adjust the flame to a very low setting to prevent carbon deposits that can contaminate the weld area.

Step 4: After preheating, place the rod or strip of polyethylene perpendicular to the surface and, where it contacts the tank surface, continue to heat the area. As the fill material starts to soften, apply a light pressure forcing it to roll forward until the entire crack area is covered. Let the filler material cool, then trim off any excess.

Step 5: For holes, push the heated rod through the hole being patched to form a plug. Add additional welding rod to the outside of the plug to form a head that is then melted to the outside of the repair area.

Step 6: Upon completion of the weld, flatten the weld area with a slightly preheated putty knife. The knife must not be so hot that it melts the plastic but hot enough to avoid a cold shock to the weld. This flattening action firmly presses the melted surfaces together while aiding in slow cooling.