The salt concentration will be highest during periods of low flow, i.e. during start-up. Since most systems will have a recirculating system on their condenser to keep evactors cool most of the water will be recirculated back to the condenser possibly increasing the salt concentration even more. Once a hotwell level has been established and hotwell pumps are placed in service any detection equipment should be in service. You want to be able to dump any contaminated water overboard as soon as it is detected to prevent it getting to the boiler.