Expert: Henry Boyter - 6/3/2004

Question
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Followup To
Question -
Hello Sir,
I would appreciate your expertise on this matter.
I have a 1500 gallon water holding tank that feeds
my centrifugal pump test stand.
The water in the tank is just recirculated when
testing pumps and just sits when not in use.
The tank is plastic but the pipe on the test
equipment is iron and the pumps are typically
iron.
Can you tell me what I should treat the water with
to control algae, rust, etc.?
Thank You,
Kris Bond
Answer -
The only way to know for sure is to have the water tested at a local lab.  Algae will be your biggest concern I think since you will get oil and other organics in the water from just the pump.  You also didn't mention the type of water.  If deionized or distilled it will be more corrosive to the iron pipe.  You have to also look at your end use.  Treatment will involve the introduction of chemicals.  Will that mess up how the water is being used?

It is currently straight tap water.
Unless the chemicals were to change the viscosity, there would be a
problem with adding chemicals.
Are you recommending that I have the water tested at monthly or annual
intervals and treat it accordingly?
Or should I add a chemical to control algae and rust from the start?
Thanks,
Kris

Answer
The viscosity will change little unless you have to add a "ton" of chemical.  If it is municipal water there may be enough chlorine to fight the algae for a while.  Unless you test it, you will not know which chemicals to add and they can be expensive.  Treat the tank like a swimming pool and just check it when first filled, for the first few months, and/or when you see visible changes.  If there are no changes after two or three months go to semi-annual and then annual.  I think you are going to see changes from you system itself.  Test kits can be gotten at swimming pool supply stores.