Newbie with some general questions

[LPCPool]

Hello everyone. I've been reading for a while (thanks to all that contribute here!) and wanted to ask some specific questions that weren't clear to me after searching through some of the other posts.

First some details about my set up:
Bought a house with 26K gallon in-ground plaster salt water pool last year. The filtering system uses DE. Being that I was (am) new at this, I elected to have a service come by every two weeks during the first season to make sure that everything was kept up. At the same time, I made a commitment to take over more of the day to day aspect begining with the second season (this year). So, I elected to have the service do the opening and closing along with a monthly schedule and hand-holding along the way if things got out of hand in between. My ultimate goal is to be able to do it all on my own.

On to the questions:
I inherited a LaMotte ColorQ tablet based kit with the house. I didn't use it at all last year, but with getting more involved this year, I've started to use it a lot more. Problem is that, after reading about the different test kits on this board and getting the FAS/DPD kit as an alternate testing method, I'm getting some wildly different results from the LaMotte than I'm getting while using the FAS/DPD at times.

Here is an exanple from today:
FC - 1.32 (LM) 5.0 (FAS)
TC - 3.76 (LM) 5.0 (FAS)

What compounds my reliability of the LM kit is that the pool service also uses a ColorQ kit (drop based) and we've done a side by side with the same water sample about 3 weeks ago and gotten some very different results.

So, the question is, which do I rely on? Given the result from the LM, I should be concerned about the CC level...but the FAS test stays clear after adding the second reagent. The FAS test does introduce some level of user error - for example, how much does the actual scoop size come into play? I've read that adding the first reagent is kind of time sensitive...maybe I'm not doing it fast enough (or too slow)?


Next questions have to do with adding liquid stabilizer:

Currently (according to 2 different test methods) I'm at 50ppm CYA. Trying to get to the 60-80 range recommended both by this site and the SWG manufacturer. I'm using liquid stabilizer simply from a convenience standpoint. Problem is though that I added a gallon when I was at 42 and after a few days and testing again, I'm only at 50. Just wondering why it didn't go higher? I've noticed that if I add it directly to the skimmer, it tends to bump up the pressure on the DE filter. So, I'm wondering if I should be diluting it first? Should I just add it to the pool water directly and forego the skimmer?

 

[JasonLion]

The ColorQ usually does fairly well, but we have heard of occasional cases where a specific ColorQ get broken somehow and diverges from reality fairly seriously.

The amount of powder used in the FAS-DPD test is not usually an issue. It is easy to add enough when FC levels are reasonable (as yours are). The only time people usually have problems with not adding enough powder is when the FC level is really high (say 30 or more). There is no risk of adding too much (within reason).

Doing the FAS-DPD test too slowly is a risk, but again at low FC levels (like yours) no one ever tends to run into the time limit. With FC around 5 you should be able to do the test in under a minute, and that should be fine. If you are taking 5 minutes to do the FAS-DPD test, starting when you add the powder, there could be a problem.

The best way to add liquid conditioner (CYA) is to pour slowly in front of a return jet. Liquid conditioner should register on the test within an hour or two of being added. Keep in mind that the ColorQ is especially finicky about how you do the CYA measurement. Be sure to follow the instructions about timing and dissolving the tablet exactly. The ColorQ also has less precision doing the CYA test than you might expect, so the result can be valid (ie within the designed error range) and yet rather far off from reality (ie +-25 ish).

 

[LPCPool]

Thank you for the respones.

The house also came with a K-2005 kit. I really don't use it all all since color matching and I don't necessarily get along. Plus, I wasn't sure how old the reagents were (given that the ColorQ seemed to be their primary kit). However, the black dot test is easy for me to do. When I bought the FAS/DPD kit, I also ordered some fresh reagent for the CYA test and both the LM and the Taylor gave the same result for the CYA level.

When I do the CYA test with the LM, I usually do a full range of tests and prefill all the tubes I'll need. When I get to the CH test, I drop both the CH and CYA tablets in their respective tubes and, while I'm crushing and then getting the CH reading, it allows me to easily wait the recommended 2 minutes for the CYA solution to sit around before putting it in the photometer.

Given both the above, I'm fairly confident that I'm getting a "true" result. I'll go ahead and add the next gallon as you suggested and then retest from there.

Do you know if there's some sort of "recalibration" or other fix for the photometer? It seems to do well with some things (like TA and CYA) but is usually off (and sometimes way off) with FC/TC, PH and CH (comparing my tests to the testing done by the pool service and samples taken to 2 different pool stores). I really like the idea of using it vs. comparator based kits, but my only other choice is to look at more professional oriented (and priced) testing equipment.

 

[steve.haggh]

If you don't know how old your reagents are, replace them. I have noticed that DPD 1A and 1B have the shortest shelf life in my kit. Usually not more than 2 seasons and you need fresh, otherwise the colorQ measurements will be off. You can order replacements online. RecSupply.com carries them.