Howdy all!

As you can see from this picture, the water fill tube leading to my water tank is not effectively connected.

For those that don't see the picture inline, the link is here: http://i.imgur.com/u5Cuayt.jpg

If you can't tell from the image, a PO took a standard PVC elbow and used a mess of silicone caulk to hold it in place. You can see the remains of what appears to be duct tape that was used to hold the fill tube to the water tank.

I would like to fix this in such a way that the fill tube is mechanically connected to the tank. Unfortunately, there isn't a large access hole on the top so I am unable to reach the inside of the tank. Has anyone solved this issue? If so, how?

Thanks,

Bob

thorndike wrote on Fri, 08 August 2014 22:43

Howdy all!

As you can see from this picture, the water fill tube leading to my water tank is not effectively connected.

For those that don't see the picture inline, the link is here: http://i.imgur.com/u5Cuayt.jpg

If you can't tell from the image, a PO took a standard PVC elbow and used a mess of silicone caulk to hold it in place. You can see the remains of what appears to be duct tape that was used to hold the fill tube to the water tank.

I would like to fix this in such a way that the fill tube is mechanically connected to the tank. Unfortunately, there isn't a large access hole on the top so I am unable to reach the inside of the tank. Has anyone solved this issue? If so, how?

Thanks,

Bob

Bob,

You have lots of problems there. (News Flash - Huh?)
By the color, I would guess that the tank was polyethylene. Nothing will stick to it without preparation.
The deck plate JR suggested might work without help, but only if it is mounted to a solid substrate. The tank goes not qualify. It may still weep if the tank is pressed up.
3M5200 will stick to the tank with "flame treatment" I will explain below, but it cannot be counted on for a long term leak-tight seal. It is also not listed as drinking water safe.
There are rubber tank grommets used in waste tanks, but I do not believe that any are drinking water safe. They are also planned only for the top of waste tanks.

For your consideration: (Thinking is the most cost effective thing to do.)
All are best if you can remove the tank and work on it in clear space.

First suggestion - Try to locate a local plastic fabricator to weld in a threaded bushing.

Second suggestion - See if you can get a large enough pipe tap and possibly thread the tank wall. You may be able to borrow a tap that size if you have a plumber-friend. Put air in the tank while tapping to blow the chips out. Use only teflon based thread paste and screw the new fitting in only hand tight.

Third suggestion - Yes, deckplates may leak, but notice this is the last suggestion. Get a deckplate. Drill it to accommodate 3 times as many screws as it was made to accept. Use only stainless (8-18) screws. Cut the tank top and Flame Treat the tank where the flange will sit. Find a drinking water safe sealant - 3m5200 is not one of those. Stick the flange in and then go find a rubber sealed bulkhead fitting for the tank wall.

About Flame Treating - This is what you do to paint or stick (non-structural) things to PE and PP things.
Mark the area that needs to be stuck to with something other than a grease pencil. This doesn't need to last long, but you need to see it to start. Take a propane torch and play it over the required area enough so you can see a change in surface texture and/or color. Let it cool. To test, drip water both inside and outside the treated area. There should be significant difference in the wetting properties. If you can not see this, do it again.

What you have just done is slightly burn the surface. So, now the surface that was poly-whatisit is no longer that material, but that surface is still part of the original material. Kind of like making it into primer.

Were I you, I would try real hard to stop at number one.

Matt

Bob,

The first suggestion is the best one.

18-8 stainless fasteners are junk and are only intended to be used during interior marine construction or such that they will not be exposed to the elements. Stick with 316 stainless as I mentioned above.

Matt is also correct that 3M 5200 is not recommended for use on a potable water system, the views on this can vary from person to person as I believe there is no harm in using it as a gasket material just so long as there isn't globs of it sitting on the bottom of my water tank.

Contrary to what some believe 3M5200 WILL in fact stick to PE provided it is used as a gasket and is secured. My only prep was to clean with Acetone.

And lastly, regardless of what sealant is used we never DRINK the water out of our potable water system, and I have a stainless water tank. Yuck!! We shower with it and do dishes and that is pretty much it, otherwise it is bottled water.

Jared

Don't do it, not with that type of deck plate. They are certainly not water tight regardless of what the listing says.

We use the exact plate at work and at best they are "water resistant". P.S. I do open hull assembly for Ranger Tugs.

If you fill your tank to the top, it will leak I guarantee it.
Jared

lotsofspareparts wrote on Fri, 08 August 2014 21:37

Don't do it, not with that type of deck plate. They are certainly not water tight regardless of what the listing says.

We use the exact plate at work and at best they are "water resistant". P.S. I do open hull assembly for Ranger Tugs.

If you fill your tank to the top, it will leak I guarantee it.
Jared

Jared - My aluminum landing craft has a self bailing deck and is designed to run completely awash. Meaning I often have 2" to 8" of water on deck. It has a sealed 3 chambered hull, each chamber has one of those deck plates. I've never had any water get in. I do checked them after each use, and clean and lube the o-rings with Dow 111 Silicone Grease. I realize that you are talking about water getting out while I am talking about water getting in, but I wouldn't think that would matter.