Water Tower interior 1

[wojton]

I've got a client with a 500,000 gal. stand pipe. Coating systems on the exterior and interior have failed. The stand pipe is the base for three cell towers so the clint receives significant rental income. They want to drain it and take it out of service, but not demo it because of the income. The problem is that they only want to paint the outside of the tank. I'm concerned about the future corrosion of the interior surfaces. Should I worry?

 

[cub3bead]

It depends on the corrosivity of the water. If you have a slightly positive LSI then you may be ok. If it is negative then you will have problems.

I would re-coat the interior with with a NSF 61 approved or state approved system.

The water system clients might object to excessive rust if not coated and the tank will likely fail and there goes the rental income too.

One problem you have is the water level in the stand pipe flucuates causing a wet/dry cycle on the interior.

 

[bimr]

If the tank is structurally sound at the present time, then you should not have any problems. You will need to install a dehumidifier in the tower. If you keep the interior dry, that will minimize the interior corrosion. That would be a humidity reading of less than 40% or so.

Steel will last for a long time if kept dry. Witness the cars out in the dry desert. If you remove the moisture, then the standpipe will last for a long time too. Don't forget to do periodic inspections.

 

[RWF7437]

Really ? Dehumidifiers in Water Towers ?

 

[bimr]

RWF7437, reread the post. "They want to drain it and take it out of service, but not demo it because of the income."

Dehumidification is a proven technique to prevent rusting of equipment.

http://www.bry-air.com/applications/corrosion_prevention/about-corrosion-prevention.html

 

[RWF7437]

Thanks bimr. Other "proven" methods of corrosion prevention include coatings, paint, cathodic protection, and combinations of these. Some do not require a continuous supply of power. Other considerations might include the structural integrity of the standpipe,its stability when empty, aesthetics, and maintenance responsibility.

 

[bimr]

Here is a better link:

http://www.bry-air.com/files/app_updates/CorrosionPrevention.pdf

Many water and wastewater treatment facilities are adding dehumidification to prevent corrosion. Dehumidification doesn't require a continuous source of power. The power cost would be minimal if the tower is closed and would only be necessary part of the year depending on the climate. It is much less expensive than repainting.

 

[JStephen]

Note that the tank needs to remain vented even if not in service. Temperature fluctuations will cause air movement in and out, or damage it if sealed up.