I was finding with my GHL KHD that my dKH numbers would bounce around. It would remain steady for several readings, then I would get numbers that were sometimes 0.5 to 0.7dKh higher than the steady state numbers. I was finding that the numbers were mostly over not under the steady state readings. So, I went off to investigate why this could be happening. I do have a mini CALRx on this tank so my ALK readings have been steady.
I decided I should go back and recheck everything with the KHD. First thing I did was remeasure my water sample line to make sure I didn’t make a mistake in the length. If you look at my picture of where my KHD is sitting in relation to my tank/sump, I have over 8’ of tubing. The number was the same as the first time, so I left the number the same. Yes, I did include the 7ml for the water filter.
Next, I went and recalibrated the pH probe and recalibrated the 3 pumps needed for the KHD. For the pumps I did 3 calibrations on each pump and averaged the numbers and entered that as the calibration setting. I did find that all 3 pumps were very consistent on each of their respective calibration tests. The new calibration numbers were pretty much spot on with the numbers I had entered previously.
I only take 2 readings per day at the default 10am and 10pm settings. So, I decided to run a set of measurements and watch how the measurement process was working to see if I could identify a possible reason why the numbers were sometimes higher. I do have the flexpvc tubing on the reagent line running from the reagent bottle all the way to the KHD reagent input.
What I did notice is that my water sample line on some of the tests would appear to have more air bubbles and at other times there were less to no air bubbles. These were bubbles in the tubing not at the fittings. I did have some bubbles at times at the fittings, but these bubbles would stay in place at the fittings and not migrate up the tubing. The air bubbles were throughout the sample line from the sump to the KHD. I checked the connections where the water filter is connected to the tubing and I also checked the fittings going into the pump head to make sure I wasn’t getting air into the line and I wasn’t. I was noticing that the water filter would sometimes fill with water and sometimes it wouldn’t and I would get more air bubbles trapped in the filter that would then release later in the process as the water was being brought in for testing. So, I put a new filter on and I was still seeing the inconsistencies in my readings and when I would get the off readings there was more air in the line.
As I stated earlier my KHD water sample line was over 8’ in length. I have an external overflow on my tank and I decided to move the water sample line to pull water from the overflow which would shorten my water sample line significantly. I recalculated the water sample line and entered the new number, including the filter. I also recalibrated pump 1 which is the water sample pump since the tubing is now shorter. I left the KHD this way and let it run it’s 2x/day measurements. I was still seeing the inconsistencies over time.
I kept coming back to the water filter and the air bubbles in the water sample line. I didn’t want to run the KHD without a filter. So, I decided to run a set of tests without the filter in the line but the SW would be filtered prior to running the test. I put a plastic container right below the KHD and shortened the water sample line. I entered the new length of the line this time leaving off the extra 7ml’s since there isn’t a filter in the line. I recalibrated pump 1 once again with the shortened tubing.
So, now I did a number of manual measurements with the KHD pulling the filtered SW from the container. For each test I also dumped the water from the container from the previous test since the KHD drains the water sample line back into the container. I didn’t know if there would be some residue of the reagent in the line. I figured go fresh with each test.
My observations were that the water sample line each time was free of air bubbles in the tubing length. There were times when there were small bubbles trapped at the fitting to the pump head, but these bubbles stayed in place. I came up with a solution for this, but that I will describe in a later post.
My dKH readings were very consistent from test to test. The most I saw was a 0.1dKH difference in the readings. I was impressed. I wanted to figure out a way to continue to use the setup using the container right below the KHD to hold the water for each sample.
So, here was my plan. I had a spare GHL Maxi Doser. I set it up where on the left pump I ran a line down to my sump and I put a filter on that line. The left pump would supply the filtered tank water to the container. The right pump would empty the container and I decided that the water would just go right back into my sump. I thought about the “freshness” if you want to call it that of the container water for when the time came for the KHD to run its measurements. I decided that I would partially fill and flush the container 2x and then I would fill it a 3rd time. The 3rd fill would be the water the KHD would use for its measurement testing. Since I run the KHD 2x/day, I could just create a set of timers to perform these functions and I would do this right before the 10am and 10pm measurement cycle. After the KHD was finished, the right pump would drain the container. I found that running the fill or left pump for 2 minutes would add around 500 ml’s of water which was plenty of water for testing. The KHD needs 80ml’s plus whatever it uses to initially flush the unit. When I was collecting the waste water it averaged out to around 100ml’s per test.
End result is that my KHD measurements are now very consistent and I am not getting the spike readings as I would call them like I was previously. I’ve been watching the container to make sure I don’t see a buildup of salt residue or anything nasty growing in it. I’m surprised at how dry the container is after the right pump drains it. I also run the right pump for a longer period of time vs the left or fill pump to suck all the water out. I also live in AZ and since it is very dry here the container seems to dry out between tests. It is also very easy to take the container once a week, clean it and rinse it with RO/DI water and put it back in place.
I decided I should go back and recheck everything with the KHD. First thing I did was remeasure my water sample line to make sure I didn’t make a mistake in the length. If you look at my picture of where my KHD is sitting in relation to my tank/sump, I have over 8’ of tubing. The number was the same as the first time, so I left the number the same. Yes, I did include the 7ml for the water filter.
Next, I went and recalibrated the pH probe and recalibrated the 3 pumps needed for the KHD. For the pumps I did 3 calibrations on each pump and averaged the numbers and entered that as the calibration setting. I did find that all 3 pumps were very consistent on each of their respective calibration tests. The new calibration numbers were pretty much spot on with the numbers I had entered previously.
I only take 2 readings per day at the default 10am and 10pm settings. So, I decided to run a set of measurements and watch how the measurement process was working to see if I could identify a possible reason why the numbers were sometimes higher. I do have the flexpvc tubing on the reagent line running from the reagent bottle all the way to the KHD reagent input.
What I did notice is that my water sample line on some of the tests would appear to have more air bubbles and at other times there were less to no air bubbles. These were bubbles in the tubing not at the fittings. I did have some bubbles at times at the fittings, but these bubbles would stay in place at the fittings and not migrate up the tubing. The air bubbles were throughout the sample line from the sump to the KHD. I checked the connections where the water filter is connected to the tubing and I also checked the fittings going into the pump head to make sure I wasn’t getting air into the line and I wasn’t. I was noticing that the water filter would sometimes fill with water and sometimes it wouldn’t and I would get more air bubbles trapped in the filter that would then release later in the process as the water was being brought in for testing. So, I put a new filter on and I was still seeing the inconsistencies in my readings and when I would get the off readings there was more air in the line.
As I stated earlier my KHD water sample line was over 8’ in length. I have an external overflow on my tank and I decided to move the water sample line to pull water from the overflow which would shorten my water sample line significantly. I recalculated the water sample line and entered the new number, including the filter. I also recalibrated pump 1 which is the water sample pump since the tubing is now shorter. I left the KHD this way and let it run it’s 2x/day measurements. I was still seeing the inconsistencies over time.
I kept coming back to the water filter and the air bubbles in the water sample line. I didn’t want to run the KHD without a filter. So, I decided to run a set of tests without the filter in the line but the SW would be filtered prior to running the test. I put a plastic container right below the KHD and shortened the water sample line. I entered the new length of the line this time leaving off the extra 7ml’s since there isn’t a filter in the line. I recalibrated pump 1 once again with the shortened tubing.
So, now I did a number of manual measurements with the KHD pulling the filtered SW from the container. For each test I also dumped the water from the container from the previous test since the KHD drains the water sample line back into the container. I didn’t know if there would be some residue of the reagent in the line. I figured go fresh with each test.
My observations were that the water sample line each time was free of air bubbles in the tubing length. There were times when there were small bubbles trapped at the fitting to the pump head, but these bubbles stayed in place. I came up with a solution for this, but that I will describe in a later post.
My dKH readings were very consistent from test to test. The most I saw was a 0.1dKH difference in the readings. I was impressed. I wanted to figure out a way to continue to use the setup using the container right below the KHD to hold the water for each sample.
So, here was my plan. I had a spare GHL Maxi Doser. I set it up where on the left pump I ran a line down to my sump and I put a filter on that line. The left pump would supply the filtered tank water to the container. The right pump would empty the container and I decided that the water would just go right back into my sump. I thought about the “freshness” if you want to call it that of the container water for when the time came for the KHD to run its measurements. I decided that I would partially fill and flush the container 2x and then I would fill it a 3rd time. The 3rd fill would be the water the KHD would use for its measurement testing. Since I run the KHD 2x/day, I could just create a set of timers to perform these functions and I would do this right before the 10am and 10pm measurement cycle. After the KHD was finished, the right pump would drain the container. I found that running the fill or left pump for 2 minutes would add around 500 ml’s of water which was plenty of water for testing. The KHD needs 80ml’s plus whatever it uses to initially flush the unit. When I was collecting the waste water it averaged out to around 100ml’s per test.
End result is that my KHD measurements are now very consistent and I am not getting the spike readings as I would call them like I was previously. I’ve been watching the container to make sure I don’t see a buildup of salt residue or anything nasty growing in it. I’m surprised at how dry the container is after the right pump drains it. I also run the right pump for a longer period of time vs the left or fill pump to suck all the water out. I also live in AZ and since it is very dry here the container seems to dry out between tests. It is also very easy to take the container once a week, clean it and rinse it with RO/DI water and put it back in place.
