Chrome plating shop has DI water compatibility issues

A. I did not think that RO water would get to 10 meg Ohm quality. It takes a good mixed bed DI system to do that. A two tank in series at that. Yes, at 10 Meg water, you will need to get all of the metal out of the system as it will attack the metal and the metal will go into your baths. Leach the PVC for several days with a slow trickle of good water going to drain. If you are serious about quality, You can not have Joe Sloppy do the glue work or you will have solvents in your water for days/weeks. Consider welding by a qualified PVC welder or go to schedule 80 PVC threaded joints with one wrap of teflon tape.

A. That was a good response, but I would recommend liquid teflon sealer rather than teflon tape. The tape is good for metal joints, but the liquid (paste) sealer is better on plastic. Follow the instructions, FILLING only the first two threads.

A. First, yes, you can get 10 meg-ohm water from an RO system - quite easily actually, with a correctly designed 2 pass RO. Why you would go this route, however, instead of a DI, or better yet, a recycling DI system (which can also get you the 10 meg-ohm you want when properly designed) is a question maybe you can answer. The capital equipment costs are about the same - perhaps a bit higher with the DI systems, but the difference is the 99.9% recycle of water vs the 70% recovery of water and 30% to drain as wasted water with some salt in it. I'd look at this before you buy!

Secondly, brass, copper, and bronze will all leach metals if you hit it with that quality water. They need to be changed. I'm puzzled that you have copper water lines to your points of use right now. You said that you had a chloride problem (chlorine?) with previous experience - but in my 24 years in the water business I have never heard of a chloride issue with good quality PVC pipe being an issue with water, with exception of some ultrahigh purity applications. Usually, its not subject to the chemical stripping effects of process baths that require tanks to be leached, etc. Water, at that purity, doesn't have that capacity to do that.

Lastly, why would you waste that quality of water to clean the de-misting pads in your MACT scrubbers? At $2-3/1000 gallons minimum for treatment to make that quality of water, its mighty expensive! Why don't you use the RO reject for that purpose if that is the way you want to go?

If you haven't purchased yet, look around Finishing.com for more information and letters regarding water recycling systems for these specific rinses. We are currently building one to process 40 GPM for less than $50K and will return at least 2-4 meg-ohm water back to the rinse tanks and sprays.

A. 10 Meg-Ohm-cm water must be a mistake. There is no need for water with a purity this high. It may be that the water quality needed is 10 µS (Micro-Siemens), which is 0.1 Meg-Ohm, not 10 Meg-Ohm. For either RO or DI water, it is best that all piping and fittings be either non-metallic, or stainless steel.