Heat effect on diluting concentrated NaOH solution I am an engineer in water treatment and have a chemistry question. In water treatment we dose $32\%$ sodium hydroxide solution for $\mathrm{pH}$ adjustment and there is a concern that our dosin lines must be $100\%$ dry before introducing the $\ce{NaOH}$ solution. This is the problem as they have been pressure tested with water and there is water residue in them.
Will $32\%$ sodium hydroxide solution react violently with cold water? It is my understanding that the reaction only occurs when solid sodium hydroxide (lye) is dissolved in water and since my $\ce{NaOH}$ is already in solution then this reaction will not take place. Is this correct?
The solution gets warmer by diluting with extra water, but no violent reaction. I suggest to do a test, if the temperature raise is concerning you, e.g. because of the tubing temperature resistance.
What  can also be done is applying solution with graduating concentration, so warming would be spreaded in sevceral steps. But as hydroxide is already quite diluted, I expect temperature change rather few than many degrees.
Another concern is initial dosage would be affected by water, decreasing concentration of the applied volume.