RO Dilution question

[Inhiding]

1.5 barrel brewer here, and the plan is to use 50% RO to get the Mg level from 40 to 20 and see if that improves the flavor, or rather gets rid of the harsh bitterness that Mg might be contributing. With our current setup our water comes in through a tankless water heater, so we have no extra HLTs available. My question is this, getting 35 gallons of RO water is no problem. Can I use the 35 gallons of RO water for the mash (use the direct fire burners to bring it up to temp, add grain and mash as usual), treated with Gypsum and Chloride, and then use the tap water through the tankless for the sparge? would this result in the same water build as if I were to combine all the water in a tank and treat?

any thoughts? if this works well I will install a RO unit and capture the water in a tank and use a booster pump to run through the tankless.

 

[Bensiff]

If I am reading you correctly, you want to mash with RO and sparge with tap? As long as you treat the RO with some salts first I don't see why it would be an issue...but, wouldn't mash with pure RO.

 

[Inhiding]

If I am reading you correctly, you want to mash with RO and sparge with tap? As long as you treat the RO with some salts first I don't see why it would be an issue...but, wouldn't mash with pure RO.

A more succinct way of phrasing my post! but yes, mash with the RO and sparge with the tap. In my mind i think it would work the same but wanted to be clear.

 

[mabrungard]

The decision to dilute the mash water with RO is dependent only on what the alkalinity of the tap water and the net effect on the mash pH. So that will determine what dilution should be applied. If the alkalinity of the tap water is greater than about 25 ppm as CaCO3, then you need to be acidifying the sparging water to reduce the alkalinity to acceptable limits and avoid leaching tannins and raising the overall pH of the final wort.

So it might be OK to use the tap water for sparging when properly acidified, but it may be more wise to use the RO water (or a large percentage) so that the sparge water is naturally low in alkalinity. RO water has very low alkalinity.

The decision to dilute the overall quantity of tap water by half to reduce the Mg concentration is sound. How that quantity of RO is distributed in the mash and sparge is dependent upon the grist and the tap water alkalinity. Figuring this out is the work of Bru'n Water.