How to clean the contact tank / precipitate tank

[Hcw3]

I have a softener system with a chlorine injector, a 120gal fiberglass contact tank, a backwash carbon filter, and then the softener.
My question concerns the 120 gal contact tank.
The system has been in operation for 4-5 years now, the installer didn't provide much in the way of a cleanout (only a ½" drain line), and I've never cleaned the iron-precipitate out of the tank. I'm thinking that the sediment may have become caked in there by now, and I might have difficulty simply rinsing the tank out. Is it likely to need 'stronger measures', ie: a high-powered sprayer, or maybe a chemical solution, that will break it up?
Or should just draining the tank be enough?
Thanks for any insight.

 

[Mikey]

I have a 120gal galvanized tank, with the outlet fitting about 8" above the bottom of the tank; the bottom is concave - pushed up, so there's a ditch around the bottom that fills up with iron sludge. I use a pressure washer to get it out about once/year. If your drain is at the bottom of the tank, and the tank is convex - pushed out, you should be able to drain it weekly or so and get the sludge out as part of the draining process. But the 1/2" drain line is a little skimpy.

 

[Sponsor]

 

[Hcw3]

Thanks Mikey. I thought the ½" drain was kind of useless. The drain can support a 1" fitting, so I'm not sure why he did the small line. I'll be replacing it when I redo the rest of it around the system, moving it all over a few feet.

The pressure washer sounds like a good option, as long as it doesn't damage the fiberglass tank.

Wouldn't draining it once per week make it tough to keep the free chlorine balanced? Doesn't your free chlorine get all wacky for a time, after you do your annual draining?

I have a 120gal galvanized tank, with the outlet fitting about 8" above the bottom of the tank; the bottom is concave - pushed up, so there's a ditch around the bottom that fills up with iron sludge. I use a pressure washer to get it out about once/year. If your drain is at the bottom of the tank, and the tank is convex - pushed out, you should be able to drain it weekly or so and get the sludge out as part of the draining process. But the 1/2" drain line is a little skimpy.

 

[Mikey]

Wouldn't draining it once per week make it tough to keep the free chlorine balanced? Doesn't your free chlorine get all wacky for a time, after you do your annual draining?

Well, in truth, I don't bother checking it right away, but since the chlorine pump injects immediately prior to the contact tank, I'm getting the right initial concentration in the tank, so I don't think the free chlorine residual is too far off. As long as I don't draw a lot of water right away, the contact time is adequate. I will check it the next time I clean it, though.

In your case, I doubt you'd have to drain more than a few gallons or so to get all the sludge out, if you drain it before it gets a chance to solidify in the bottom hemisphere of the tank. Watch the outflow as it's draining, and as soon as it runs clear, shut it off.

 

[Hcw3]

Mikey, Good point about partial draining. Thanks.

I appreciate your input. I'll have to see how hard/caked the sediment has become. Hopefully it will wash out with no problem at all!
Thanks again.