Pool Staining from Granular Trichlor

[NLITP]

Hello. I moved to a home having a newly resurfaced (pebble) pool and knew absolutely zero about pools and pool maintenance a few months ago.

A pool service shocked the pool using granular trichlor, which sat on the pool service for a few days (even though I was told initially it would dissolve in a few hours). I'm sure some staining took place where the granular trichlor sat on the pool surface, but being a newbie pool owner, I didn't really notice it at the time. A month later, on a weekly service visit, I am informed I have no chlorine in the pool, so it must be shocked again - granular trichlor once more. This time, it was obvious to me where the trichlor laid on the pool surface, it was leaving behind stains. Someone from the pool service has since verified the granular trichlor was indeed staining the pool. The color of the stain is difficult to determine because of the pebble, but I'd guess brown-ish(?).

I've since found this forum and have learned a lot. I have a Taylor 2006 test kit and have been testing for about the last 2 weeks while keeping the pool service going. Here are my current numbers (though I don't have any numbers for the time in which the stain occurred, unfortunately):

FC - 2.5
CC or TC - < 0.5
pH - 8 (possibly a tad more, but Taylor only goes to 8.0)
TA - 90
CH - 230
CYA - 68

I realize my PH is high and chlorine is low (based on my CYA of 68). My saturation index is about a 0.4.

Q1: Should granular trichlor be staining my pool's surface? The pool service says it is how they service all of their pools and that after an acid wash, the same treatment should not stain my pool (they believe the pool was never acid washed). The last thing I want is to acid wash the pool and then it get stained again by throwing granular trichlor at it.

Q2: Can anyone advise me on what I can try to remove the stains other than a complete acid wash?

Thanks!

 

[Patrick_B]

Welcome to the forum!

Unfortunately I can't say if an acid wash will even work, and would not be surprised if it didn't. If the stains were from TriChlor lying on the surface, the pigment in the base finish and or colored pebbles is likely bleached out. How Acid wash would repair that is beyond me, but I would not count on on it. Terrible, terrible Idea to ever let granules rest on the bottom like that in any pool. Just for the record, having a prior acid wash done to a finish will not prevent it from being damaged by granules lying on the surface. If there is color left, then there is color to be bleached out. If they are saying it bleached out because you never had an acid wash treatment, they are lying, incompetent or both. Nonsense!

So right now, you need to get the pH down, and the Free Chlorine up, or you are about to have a green swampy mess. If you don't have a Salt generator, I would suggest reducing the Cya to 50, but at least get the FC up to proper range for 70. You can't see 68 on the Cya test, and anything significantly over what you think is 65 should be viewed as 70, and without salt, that is too high. You can only reduce the Cya by removing and replacing water, but it won't be much if those numbers are close. Ditch the pool service, and let's get this under your control.

 

[cowboycasey]

we can help you take control of you pool if you want You already have a good test kit so your well on your way

Here is the CYA FC chart that Patrick was talking about Pool School - Chlorine / CYA Chart

read up on pool school Pool School - Pool School

keep that FC above 8 at all times using bleach/liquid chlorine/pool shock... You do not want to use tri/di chlor any more as that will raise your CYA... Tell the pool company or they will continue to add..

 

[NLITP]

Thanks so much for the helpful feedback. I went to the "big store" today and had my water tested to see if it was a close match to the numbers I posted yesterday. It confirmed my PH is 8.0 and total alkalinity is 90. However, it says my CYA is at 40 (not close to 70 as I had read). I just retested the CYA and maybe it looks closer to 50 or 60(?)... it is the hardest test for me to interpret with the Taylor-2006 kit, unfortunately. Not sure whether to go with the "big store" number or my own in this case... maybe call it 50(?).

So, here is my plan to get my numbers right based on your feedback... please correct me where I mess up:

1. Add muriatic acid and retest 4 hours later, etc. until I can get the PH down to around 7.5.
2. Based on a CYA of 50, add enough liquid chlorine to reach 6 ppm of FC.

After my numbers are looking better, does anyone have anything for me to try in regards to removing the stain? Should I bring the chlorine up to shock level before bringing it back down to 6 (would it help in regards to the stain at all??).

Really appreciate the feedback and learning lots from this forum.

 

[NLITP]

For those boys and girls following along at home, here is the latest...

I added MA on 7/17 and kept doing so until I reached a PH of 7.6 and my FC is up to 4.5 with zero CCs. Yesterday I inspected the pool stain and it appears to be lighter than before though hard to say with 100% confidence. Does this sound possible given the only changes have been lowering pH and raising FC?

While the stain is easy to see while standing on the deck looking down (8 ft deep pool), when you are down at the bottom, the stain appears faint. I tried taking a vitamin C tablet and holding it to the stain, but since the stain appears faint while under water, I can't tell if there is any difference. I don't appear to have any stains that are not at the deep end, unfortunately.

I plan to bring the pH down to about 7.4 today followed by rechecking my TA and pushing it up to about 100 (last I checked it was decent at 90) while continuing to monitor the stain for the next few days to see if it is indeed lightening. Please comment if there is anything else someone feels may be helpful. Thanks.