What do you all reckon to the spotless water things that are about? Just been reading the thread.
I've been in a similar situation to yourself....live in a rock hard water area, spent many brews using Tesco Ashbeck water as a water low in mineral content. I bought an RO system, used it for maybe 8 brews, got fed up with the time required to produce 30L or so of RO and was also never comfortable with the amount of "waste" (in quotes because I know its not truly waste and can be used for many things) water. Even after I'd got a water butt.....two brews and it was full and in winter there was no way I'd be using the waste "water" for much, so once the butt was full it wouldn't be long before the bypass product was going down the drain.
I've been using Spotless for about a year now. I can detect no issues with the beer brewed using Spotless water and I have no concerns about the water sitting in pipes in the Spotless system.....if you saw the number of window cleaners queuing up to fill their tanks it you would see that the throughput of the system almost rivals that of a pump at your local petrol station.
My "local" Spotless filling station is a 38 mile/ one hour round trip - now that might sound like a hefty trip but when you consider a trip to my local Tesco would be maybe a 15 mile/40 minute round trip, or that it might take 5 or 6 hours to produce the required amount of RO water....it puts it into a bit of perspective....and usually I can tie my trip in with something else that I need to be doing in the rough area where my Spotless station is.
I personally would never go back to a domestic RO system, having used Spotless. Its not difficult to check on the TDS of the Spotless stuff yourself with a simple meter, but the systems do have a readout which tells you what the current TDS is (assuming you are willing to trust it!).
One caveat (and this holds true for the domestic RO systems as well as Spotless)...A lot of folks in my brewing club have used Spotless/RO, or regularly tasted beers that exclusively used Spotless/RO water, and we all agree that there is something lacking in beers that are 100% RO...they are not as rich in flavour, being a bit one dimensional. We've concluded that it is best not to use neat RO water but to cut it with the domestic tap supply....there are minerals within your domestic water supply (over and above the half a dozen or so that us brewers tend to focus on) that are useful to yeast health (zinc for example) that we typically don't put back when we add the traditional brewing salts. Its useful to keep a little bit of the minerals in the domestic supply as part of your brewing water.
What this allows you to do is to blend RO water and your tap water in varying amounts, depending upon the beer being brewed, and if you are clever enough you can create blends that then naturally limit the salt additions that you need to make to the bare minimum.
Oh yeah...according to ASDA's website, 4x2L bottles of Natural Still mineral Water will cost you £1.25 or 15.6p/L....Spotless works out at 4.2p/Litre and you don't have to worry about taking all the empty plastic bottles down to the recycling centre when you've finished.