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craigc51

Leaking sensor on freshwater tank

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 I have a small leak on one of the sensors on my freshwater tank and looking for a solution to stop the leak is there any sealant epoxy or any other fix without taking the tank out and replacing it . My understanding is that the sensors are spun in which heat up and bond to the tank 

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With a few assumptions since I don't know what the specifics are yet...

Where is the leak specifically? Is it on the spin-on fitting or is it in what connects to the fitting?

If the leak is in the tank or the spin-on fitting, it will be difficult to find a sealant or epoxy which will stick to it for more than a few minutes. Really hard to bond to poly, which is why they use the spin-on fittings. If you just gubber it up with silicone or sealant of some type, you'll make it really difficult to do a proper seal on it later on.

For pin-hole leaks, I have had some success using a clean soldering iron to carefully melt the plastic around the leak and create a seal. If you want to try this, there are lots of YouTube videos. Make sure that the plastic is bone dry and as clean as you can get it. It's possible to make the situation worse quickly with this method, so proceed with caution if you are uncertain.

If the leak is in the sensor or where the sensor connects to the spin-on fitting, then the solution would probably be easier but depend on how the sensor is connected to the fitting.

Perhaps you can post a photo of the sensor/leak? Also, a few more details like the make/model of your RV and the specifics on the sensor would help us help you.

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That's what happens, when you don't have a boat anymore!  J-B, best there is for small areas.

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1 hour ago, manholt said:

Yes,  it's called Plastic Bonder!

From the JB Weld site:

Q:Is there anything that J-B Weld WON’T bond to?

J-B Weld will not adhere or bond well to: Any flexible rubber surface, Leather,  Vinyl,  Canvas!  Polypropylene plastic,  Polyethylene plastic

 

Nothing will stick well to poly tanks. That's why they use heat welding or spin welding.

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Craig,

Might I suggest that after you get your leak stopped with the product that Carl suggested, that you consider changing a sensor that mounts on the outside of your tanks. the sensor that are mounted on the inside of tanks are notorious to malfunctioning. Sea Level is the unit I installed and they work very well. and all are mounted on the outside of the tank.

There is another product I am getting ready to use called Flex Shot. It is by the company Flex Shield. I will give it a try and post the results here.

Herman

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35 minutes ago, richard5933 said:

J-B Weld will not adhere or bond well to: Any flexible rubber surface, Leather,  Vinyl,  Canvas!  Polypropylene plastic,  Polyethylene plastic

The Waterweld (link above) calls out Potable water tanks, no mention of not bonding to polyethylene. The plastic Weld does state it will not bond to polyethylene.

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1 hour ago, jleamont said:

The Waterweld (link above) calls out Potable water tanks, no mention of not bonding to polyethylene. The plastic Weld does state it will not bond to polyethylene.

Haven't used Water Weld - might work based on some online reports.

First stop would be a to determine what the tank is made of and then to use the appropriate product. Depending on where the actual leak is, it might just be a mechanical issue (loose sensor fitting, etc).

Heat welding would be a good solution for someone able to do it, but if an adhesive or sealant is available which is safe for drinking water that will bond with the tank that might work as well.

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Most factory tanks are ABS, not poly. To test which it is, PVC glue, is a solvent which actually chemically welds PVC pipe together, so place a small piece of PVC pipe on the side of the tank using PVC glue, hold in place 10 seconds, if the pipe stays then your tank is poly. ABS is heat weldable and a similar test using ABS pipe and ABS glue.  Of course you must clean either thoroughly for adequate results. If it is ABS then the heat process will work well, if poly, then the pvc glue will probably be enough to seal and hold for a long while.

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2 hours ago, kaypsmith said:

Most factory tanks are ABS, not poly. To test which it is, PVC glue, is a solvent which actually chemically welds PVC pipe together, so place a small piece of PVC pipe on the side of the tank using PVC glue, hold in place 10 seconds, if the pipe stays then your tank is poly. ABS is heat weldable and a similar test using ABS pipe and ABS glue.  Of course you must clean either thoroughly for adequate results. If it is ABS then the heat process will work well, if poly, then the pvc glue will probably be enough to seal and hold for a long while.

Do you have that right? I thought that poly was heat weldable and ABS was able to be solvent glued. There are special solvent glues made just for ABS. If the tank is ABS then it's a much easier fix. If it's the tank itself that's leaking. PVC is a totally different type of plastic and has specific solvent glues.

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Where after checking everything online to what I can use I went to Harbor freight and bought a plastic welder and weld around the outside of the sensor which is also  polyethylene  with the metal sensor in  the center . I figured if I did  any damage on it I could take it up to Coburg Oregon . there’s a shop  that spin welds fittings and sensors onto a new tank  he also told me that welding it is the fastest and easiest way  . So far so good on the welding no leaks at least I have an option if it does leak I can replace the tank .

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3 hours ago, richard5933 said:

I thought that poly was heat weldable and ABS was able to be solvent glued.

Actually spin welding seems to be most recommended on both ABS and Polyethylene. Here is youtube video. Great job craigc51, hope it lasts as long as you want it to.

 

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Great job on the repair. What type of plastic welding did you end up with? I've got one which is a very narrow/concentrated heat gun with a metal foot for feeding the 'welding rod' into the seam. Curious to see photos is you've got any of the repair. It's nice to see how others do this since I'm sure I'll have more repairs in the future.

48 minutes ago, kaypsmith said:

Actually spin welding seems to be most recommended

Correct - and spin welding is basically another form of heat welding. In the video the Dremel is used to spin the welding rod fast enough that friction heats it up enough to melt it into the substrate. When fittings are installed with spin welding it's the same thing - spin them fast enough so that they melt into the tank surface.

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Hopefully it holds up. I’d hate to see you have to replace the tank, I can only imagine the cost.

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Heat welding works well and is often a permanent repair. Bill is correct - getting things cleaned first is key, otherwise you'll just incorporate the dirt in the repair and a leak-free repair will be almost impossible.

My tanks were custom built in 1974 from 3/8" thick polyethylene sheets. The pieces were heat welded together. Except for one 6" stretch of an upper seam which looks like it was missed at the factory, the tank is still leak free and going strong (knock on wood). I repaired the 6" piece of the seam and it has held tight since. Hopefully the repair in this thread will last a long time and you'll be able to avoid buying a new tank.

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 Richard 

 I bought a harbor freight hot air plastic welder . I had enough material on the sensor that was spun weld into the tank to move some of the plastic around where it was leaking . If it leaks again I already ordered some more plastic rod  which I didn’t have to start with . The soldering iron one which is 80 W is probably the best to start with you can smooth out any rough spots  and holds the welding plastic rod  I now feel confident that any repairs on freshwater tanks are holding tanks that I can repair now knowing that these tools  can do the job  One important  thing On buying a hot air welder from Harbor freight read the instructions if not you’ll burn it up.  When done  turn the heat down to zero and let the blower run for three or four minutes . There are a lot more welders out there for sale the skies the limit on price but for what I have to do and hopefully only needed maybe once it was a good buy. Thanks to all who respond this is one of the reasons why I joined 

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