There’s no-reading” syndrome? Nitrates in your pool water can cause a high sanitizer demand even with a pool that is crystal clear. Nitrates can be added thru many sources including but not limited to make-up water, rainwater, lightening storms, yard and farm sprays and you. After testing for and confirming the presence of nitrates, the process to eliminate them is simple-just keep adding sanitizer. Unless more nitrates are added to your pool, the chlorine will eventually burn up the nitrates and you will be able to maintain a chlorine level.