Rust in water tanks

[dstrout]

I just opened one of my water tanks for the first time and saw that I have a bunch of rust around the seams.



I'm inclined to take an electric power washer to the inside and try to blast that rust off, along with anything else on the sides of the tanks while they are open.

That leads to two questions. First, would it be a bad idea to power wash the tanks & rust (using water only, no chemicals), and second, how do I keep the rust from coming back? There is also rust along the bottom seams on the outside, so I'd like to stop it before it rusts through.

Being half way through replacing a rusted out galvanized metal diesel tank, I'm now on a war against rust and leaking tankage.

Thanks,
Dave.

[Pete7]

I seem to remember something about not using galvanised steel for diesel tanks which is why you are probably swopping them out. I think platic is the dogs danglies for diesel but our mild steel tank isn't far behind having lasted 25 years in the cockpit locker.

Is the water tank mild steel, hence the rust?

Pete

[oceannavigator]

You aren't going to stop rust with a pressure washer.

In my last boat, I had rust in the corners/welds of my stainless steel water tanks as well.

There is no practical solution. Once that rust starts, it is going to continue inside a water tank. It seems to me that mine started as crevice corrosion. In the welds/seams. I suspect yours is the same?

On the bright side, rust isn't unhealthy if you are drinking water from these tanks. Also, you could stil get several years of service out of them.

[dstrout]

Originally Posted by oceannavigator

On the bright side, rust isn't unhealthy if you are drinking water from these tanks. Also, you could stil get several years of service out of them.

Well, they've given 29 yrs of service so far... I don't mind keeping them til they fail - 75 gal of water in the bilge is a much smaller deal than 75 gal of diesel.

If there's a way I can extend their life, I may as well. Didn't know if there was a coaing I could use on the inside after power washing (or sand blasting for that matter).

I'll probably wash them anyway, since they are currently bone-dry. It's a good time to open them up, inspect, and clean.

Not exactly sure what to clean them with other than high-pressure water? Doesn't seem like there is any real need for bleach. Maybe just a rub down and rinse with bleach wipes, just to start out with a lower bacteria & algae spore count? Or is that a waste of effort?

[Pete7]

Bottle of strong bleach is cheap enough, chuck it in, leave for a while, run the taps to flush the pipes then drain and flush again a few times.

I do it annually.

Pete