Chemical dosing for cooling tower water

[u/Trigathoras69]

Hello guys, junior engineer here. I was given the task to install a control panel to inject chemicals for cooling tower water and design the suitable piping pathway and where should the chemicals be injected into the cooling tower system. I was thinking of just directly inject the chemicals into the cooling tower basin, but since the cooled water in the basin is stagnant, im afraid the chemicals will not mix well inside the basin. My supervisor suggested do the piping to that the chemicals are injected into the header at recirculation pump discharge side. The constraint with this idea is that the header is made of stainless steel, and the chemical piping is PVC. I would like to ask for any ideas or comment from you guys, especially for those who are working with cooling tower. Is there any industry standard on how to inject the chemicals into the cooling tower system?

[u/gnatty_bumppo]

It's common to design a circulation loop on the cooling tower basin that has inline monitoring and injects treatment chemicals directly into the discharge back to the basin. Chemical metering is usually handled by peristaltic pumps. Circulation of the basin water is typically handled by a centrifugal pump. You can get away with a simple control scheme.

[u/zz_Z-Z_zz → u/gnatty_bumppo]

Exactly. And pvc piping can be ordered in the same schedule and threads as the stainless. Just need a check valve and make sure the process pump discharge is not higher pressure than the treatment pump discharge, assuming it is not a positive displacement pump. Really nylon tubing (or other tubing that’s compatible with the solution) would be fine too if the dosage flow is relatively low.