RO and niter

Hello maple syrup making community

Our family has been making syrup for about four years now on PEI and we are learning alot as we go, tackling each challenge as it arrives. We tap about 150 trees and we are boiling in a small la Pierre waterloo evaporator with the flue pan at the back and the finishing pan at the front. Until this season we boiled down the sap and then bottled by hand and had no real problem with niter. We filter really well. This year we added a RO set up and also a urn with a thermostat for bottling. And have discovered a serious niter issue. Because we are new to the RO process we are not sure if the nitre is from that process and if so how to resolve it, or if its being caused by using an urn for bottling. We first figured it was the urn and we adjusted temp on a bottling test but still have niter in our bottles. I read that maybe the RO could be the source of the niter.

Our regular filtering process is as follows and maybe a little overkill . We strain the sap as it comes from the woods, now it goes through a filter and 4 membranes in the RO system, we filter with a pre filter and a felt cone filter and two additional pieces of felt filter as it comes off the evaporator. We finish on the stove and filter again with the prefilter , felt cone and two additional felt layers and as its going into the bottles use one piece of prefilter as its bottled. Im not sure how we still have niter after all the filtering. Does anyone have any suggestions? About what's happening and how to fix it?

Thanks in advance for your time and expertise

RO does not cause niter. It does however concentrate the minerals as well as the sugar, so it will form faster as concentration increases.