I thought I would post my recent success using HTH Metal Control to remove some iron staining in my pool but first a little background information...our pool install was completed last October, filled with water and started up to make sure there were no pluming leaks, all the equipment worked, etc. The following day I took water to Leslie's for initial testing with the following results:
FC - 0
TC - 0
pH - 7.8
TA - 110
CH - 190
CYA - 0
Cu, Fe, phosphates and salt were all zero.
All results were identical to my LaMotte kits with the exception of metals and salt which I did not test. Two 182oz jugs of bleach were added with about a half gallon added daily to keep some FC in the water. I wasn't testing regularly since we weren't swimming in the pool, I just wanted to keep it clear. I closed the pool in mid November when I finally got tired of cleaning leaves out of it
Fast forward to early April...I opened the pool and it was full to the rim with green water. Excess water was drained, 3 lbs of CYA were added and the shock process was started and completed in about a week. I took the water to Leslie's again and the pH, TA and CH and CYA remained the same as above. At this point nothing other than bleach and CYA had been added to the pool. Leslie's did try to sell me some Alkalinity increaser and pH decreaser but I told them I had some and left. Funny how they didn't try to sell me any CYA since their test results indicated zero.
The pool remained crystal clear up until the constant rains of last week. I didn't test much due to the rain which raised the pool volume by 2-3 inches and also considerably clouded the water. After a round of tests my FC and TC were zero and my pH still tested at 7.8 (upper limit of kit) so I started the shock process again. Friday's weekly TA test indicated that the TA had risen to 140! Now that the water was clear again I noticed an orange ring around the pool. The Vitamin C test indicated iron staining so I started to lower the TA and pH to try and control the staining. I was able to lower my TA to 110 and get my pH to 7.5 on Saturday with one round of MA treatment.
I found HTH Metal Control for $11 at Wal Mart while grocery shopping Monday morning. I figured it was worth a try since I was going to need a sequestrate anyway and this was an HEDP product which is recommended here. One quart per 10,000g is the recommended dosage for a newly opened pool and two quarts is recommended per 10,000g as a stain treatment. I purchased two quarts.
After reading about sprinkling Ascorbic Acid down the sides of the pool to eliminate staining I figured why not? I turned off the filtration, got in the pool (probably not the smartest thing to do), pressed the bottle against the wall and started slowly squeezing the HTH Metal Control around the perimeter of the pool. I could actually watch the acid moving down the wall as I applied it. The first quart made it about three quarters around the pool so I opened the second bottle and finished. By the time I got back to were I started I could see some of the stains had already disappeared where I first applied it! Some spots were clear and some were "streaky".
Since the directions say to leave the filtration running and brush the pool I restarted the filter and brushed. After about an hour I came back and the sides were still stained so I added the rest of the second bottle to the pool, left the filter on, brushed the sides again and went inside. A couple of hours later the sides were completely stain free and the slight staining on the steps and bench were also gone!!!
Out of curiosity I tested the water:
FC - 0
TC - 0
pH - 6.8 (or lower)
TA - 90
The HTH Metal Control seems to have used up a good deal of chlorine, reduced my TA around 20ppm and dropped the pH at least 0.7 and probably more. An afternoon of aeration and the pH appears to be steady at 7.5 with the TA at 90. Both the pH and TA are the same as of this morning's readings.
I'm unsure if my results were atypical since my pool is new, the stains were new, or if it was my application method (again, probably not the best idea to apply this while in the pool) but it seems to have worked wonders for me. I now wish I would have been more patient and allowed the metal control to work overnight to see if a smaller dosage would have worked but I'm still happy the stains are gone
If I am not mistaken, I will now need to try and lower my TA a bit more to get my pH in the 7.2 - 7.4 range to prevent the stains from returning in the event I need to shock the pool again.