Discrepancies between BioGuard water test in store and TFTestKit

[rendx]

Hi All,

I've been taking my water to get tested monthly at the local reputable pool store. They use the BioGuard testing equipment for it. The problem I'm having is that the results for store vs the test kit are off in a few areas. Just wondering what I should be following. I really only take it to the store to ensure my equipment warranty stays intact (requirement from pool builder). I tested my water as soon as I got back from the pool store. The only real change is that I added stabilizer about a month ago and it's really made the FC climb fast in the pool.

TFTestKit vs BioGuard machine
FC - 5.3 vs 5.4 (close)
CC - 0
Ph - 8.0 vs 8.1 (close) -> because the chlorine climbed, I'm assuming the Ph went up along with it. I reduced it from 8 to 7.6 about a month ago when my FC was at 2
TA - 120 vs 76 (?)
CH - 130 vs 118
CYA - 90 vs 101

Also the salt reading (Aquarite vs store)
2738 instant / 2894 avg vs 2297 (does this seem really far off?)

Should I be worried about anything? I'm going to reduce the FC by reducing the SWG runtime and reduce the Ph. The pool store wanted me to increase the TA to between 80-125 and increase the total hardness from 118 to between 175-225..

First year with the pool, so not really sure who to trust!?

 

[IceShadow]

I believe many stores will adjust the TA based on the CYA.

Your CYA is a bit high. I would drop to 80 or 70. See this chart for recommended FC levels: Chlorine / CYA Chart - Trouble Free Pool Note, we recognize that CYA level lowers the available chlorine from your FC total that actually does work so we recommend higher than the industry does as it hasn't caught up to that relationship yet.

The store is used to people with pucks. If you raise your TA your pH will rise faster. You have no reason to raise hardness in a vinyl liner pool.

 

[mknauss]

Precision does not mean accurate. It is fine you are getting the store test for a warranty, but I would file them with that paperwork.

You have a vinyl pool, you do not need calcium.

Your TA is high. But as you keep your pH in the 7's, it will lower. And some of it is due to your high CYA. Lowering that some, as Dustin says, would be a good idea.

Your FC is fine, if not a bit low. For a CYA of 90 the minimum is 5, but target is 7. I would raise your FC to 7 ppm.

Salt, if you do not have a K1766 salinity test kit, who knows. The SWCG is within 500 ppm most of the time.

 

[RMcGirr83]

The bioguard test is always off from my tests. Im doing the same thing you're doing, taking water samples in for warrantee stuff. I then file the test results in a folder in my office.

 

[markayash]

Close enough, plus i have noticed on my taylor if I wait between drops on TA it changes and goes back green until I add another one

 

[Newdude]

Just food for thought : we have 2 testing devices at home (non pool related) that are only accurate to +/- 20%. One can read 80 and the other 120 and technically they are both correct. Does anybody know excatly how accurate all thrse tests are ?

 

[rendx]

Precision does not mean accurate. It is fine you are getting the store test for a warranty, but I would file them with that paperwork.

You have a vinyl pool, you do not need calcium.

Your TA is high. But as you keep your pH in the 7's, it will lower. And some of it is due to your high CYA. Lowering that some, as Dustin says, would be a good idea.

Your FC is fine, if not a bit low. For a CYA of 90 the minimum is 5, but target is 7. I would raise your FC to 7 ppm.

Salt, if you do not have a K1766 salinity test kit, who knows. The SWCG is within 500 ppm most of the time.

Thanks guys. At the beginning of the year, I had a CYA of 0. I had to put a bunch of stabilizer in to get it where it is. What's the easiest way to reduce the CYA down to 70/80?

 

[mknauss]

Drain some water. It is a direct relationship to reducing the CYA level.

 

[rendx]

Thanks. Guess I'll just backwash a little longer next time.

 

[mknauss]

You need to drain about 15-20% of the pool volume.