plastic tank repair

nothing simple about a crack in one of the side walls of a poly tank

it flexes with water level and can flex under stress while in motion

while screws, bolts, well nuts, may stop the crack from enlarging, they don't stop the crack from leaking

its a crack not a pin hole

I'd go with some kind of screw. Might tap the holes and use nylon screws but there's nothing wrong with SS screws or well nuts as suggested. If you want to spend the money to buy and install an new tank I guess it's your money but that seems like a lot of expense for a pretty simple fix. Kind of like getting a new engine when you really only need spark plugs.

Tom/Barb wrote:

MrWizard wrote:
Poly tanks seldom get holes
What happens is they crack, usually in the side
One senario
Some body sticks the water hose in the fill spout and walks away
Comes back later water pourng out of fill spout
Tank gets over pressurized and cracks

Some people have sealed the crack with eternabond tape

And before someone says that won't work, they do advertise it for sealing fish ponds and pools

And yes those are usually done on the bottom of the pond/pool
So it's internal pressure helping to hold the tape in place

Klutz, drilled thru the outer bulkhead and drill 3, 1/4" holes near the bottom of the tank.
They now have plugs in them. I want a permanent repair. or it gets a new tank. but the pipe connections are glued in with something. What,,, is the question.

Why not use the Sending unit Well Nuts I mentioned??????? They work and seal good enough for millions of RV's over the past 40 years. Doug

Matt_Colie wrote:
Tom,

While MDPE is not difficult to weld, it can not be done with air. You have to have a welder that uses at least nitrogen or some other gas.

If you want to get technical and buy the tank, regulator, etc to use Nitrogen that is a recommended practice, but we are talking about a RV water tank and not a critical application such as something to be used in a factory or chemical plant. When you use air it slightly changes the MDPE's chemical or molecular composition, or so they say, but I've welded at least 8 cracked RV tanks over the past 10 years for people using air, as well as so many kayaks I've lost count, and never had a call back. I guess a bonus would be if you did buy the Nitrogen setup you could then use it in your RV tires.:D

Tom/Barb wrote:

MrWizard wrote:
Poly tanks seldom get holes
What happens is they crack, usually in the side
One senario
Some body sticks the water hose in the fill spout and walks away
Comes back later water pourng out of fill spout
Tank gets over pressurized and cracks

Some people have sealed the crack with eternabond tape

And before someone says that won't work, they do advertise it for sealing fish ponds and pools

And yes those are usually done on the bottom of the pond/pool
So it's internal pressure helping to hold the tape in place

Klutz, drilled thru the outer bulkhead and drill 3, 1/4" holes near the bottom of the tank.
They now have plugs in them. I want a permanent repair. or it gets a new tank. but the pipe connections are glued in with something. What,,, is the question.

Not glued in.........spin welded.

SPIN

Congats, you get to be the Guinea pig and see if this stuff really works. :B
Poly weld adhesive

You might get cancer, according to the warning, but they say it will fix your tank.

MrWizard wrote:
Poly tanks seldom get holes
What happens is they crack, usually in the side
One senario
Some body sticks the water hose in the fill spout and walks away
Comes back later water pourng out of fill spout
Tank gets over pressurized and cracks

Some people have sealed the crack with eternabond tape

And before someone says that won't work, they do advertise it for sealing fish ponds and pools

And yes those are usually done on the bottom of the pond/pool
So it's internal pressure helping to hold the tape in place

Klutz, drilled thru the outer bulkhead and drill 3, 1/4" holes near the bottom of the tank.
They now have plugs in them. I want a permanent repair. or it gets a new tank. but the pipe connections are glued in with something. What,,, is the question.

I had a leak in a camper's polyethylene water tank 20 or so years ago (pre-internet). Tried several products that seemed like they ought to work, but nothing seemed to stick to the tank. Finally, someone told me that welding was the only option.

It was a small crack near an embossed trademark, stamped in the side. I used a big soldering iron, and ran it along the crack, adding extra plastic shaved off a fitting on the side. It wasn't pretty but it sealed and lasted for several more years, before I sold the camper.

Poly tanks seldom get holes
What happens is they crack, usually in the side
One senario
Some body sticks the water hose in the fill spout and walks away
Comes back later water pourng out of fill spout
Tank gets over pressurized and cracks

Some people have sealed the crack with eternabond tape

And before someone says that won't work, they do advertise it for sealing fish ponds and pools

And yes those are usually done on the bottom of the pond/pool
So it's internal pressure helping to hold the tape in place

Tom,

While MDPE is not difficult to weld, it can not be done with air. You have to have a welder that uses at least nitrogen or some other gas. (I do not know is CO2 would work.)

Do not bother with any epoxies or adhesives as they will not work and may poison you while failing.

As they are drilled holes, a mechanical fix may be your best answer. Just be sure to use either 316 stainless (8-18 may not last as long) or titanium.

I did a lot of plastic tank work some years back and got to make a lot of first hand mistakes.

Matt