Hi Tim and hello friends,
the SSWS was extensively tried and tested before the start of the Shuttle program. It was constantly monitored by sensors and it is not just painted after each launch, any damage is of course repaired. 
Therefore here are some interesting information for better understanding.
At the beginning of the Shuttle program, the SSWS consisted only of these 6 Rainbirds, here during a test with the Enterprise (1979).
The same system was used during the first launch of STS-1 (1981).
The sound pressure during liftoff was greater than anticipated. In addition to the partial damage on the MLP deck,
a thorough inspection revealed that around 1% of the Columbia’s heat shield tiles had been damaged during the launch. 
That is why the SSWS was modified and improved before the second mission STS-2, 
both by the Water bags suspended in the Blast chambers,
and by the system of the Ring lines with the outlets surrounding them, what looked after liftoff like this.
For anyone interested, here is an impressive video of a SSWS test. 
And then I came across this impressive video,
in which the effect of the SSWS is demonstrated in a model test. You will be amazed. 
