Pool Balancing -- After acid bath (first dose of dichlor gives green tint to water)

[maxjar10]

Hi All,

My new pool got an acid bath to expose the aggregate quartz (Pool was filled just over 1 week ago). I was able to neutralize the acid using a combination of soda ash and baking soda. Unfortunately I overshot the TA by a little bit but not by much. My current numbers are:

PH: 7.6
TA: 110
FC: 3
CC: 0
CYA: 0
CH: 325

The acid bath was completed and brought back to neutral 3 days ago. It took some time to clear up the water from all the plaster dust that came off during the acid bath. I cleaned my pool filter which was very dirty. Now, I had not added chlorine to the water as the CH was high after the acid bath and I wanted the TA/PH adjusted a little better.

Last night I had added my first dose of 4oz of dichlor at around midnight. When I woke up this morning the water had a greenish tint to it (but very clear). I have 0 CYA in the pool and so this morning when I checked my FC it was basically 1 and so I added another 4 oz of dichlor. After waiting about an hour and checking the water it is FC: 3 but CYA still doesn't register. My thought was that I would still continue adding the dichlor in 4oz doses as necessary to maintain the PH and the CYA would eventually begin to register.

From reading other posts it seems likely that there is metal in the water (iron/copper). The other reason I highly suspect this is related to the dichlor is that the dichlor was added to the pool and was not being circulated into the spa. The spa is still clear and has no greenish tint. A sequestrant was added before the acid bath was started.

Will this green tint go away on its own? Should I cease using the dichlor and go get a chlorine stabilizer and use bleach instead? Add more sequestrant? Go get the water tested?

THANKS!

 

[Texas Splash]

If you do have metals in your source water, the water will react when the chlorine (FC) grows higher. A lot depends on the amount of metal in the water. I would also note that as your pH rises (common with new plaster) it will enhance that reaction as well. I am still however concerned about algae, even though you highlighted the difference between the pool & spa. For your water to have no CYA and very low FC for 3 days in this summer heat, it's just a matter of time before an algae bloom explodes.

If you have been turned-loose from your builder/plaster contractor and have total control of your pool chemistry, there might be a couple things you could try:
- Switch to regular bleach for now to maintain an FC of about 3 ppm. In the meantime, increase CYA with granular stabilizer to about 40 ppm. Once the stabilizer is all dissolved in the water, slowly increase FC to about 5-6. See if the water condition changes.
- Keep pH on the lower end for a few days during all of this - about 7.2-7.4.
- Consider taking a source water sample to the pool store for free testing. Only be concerned with the iron/copper numbers as you leave with the free printout. Don't get roped into any magical potions over there.
- Might be good to post a pic of your water for us to see.

Ideally algae would be the better of the two, even though we don't like to "SLAM" a new plastered pool. Metals is just more work and expense for you with chemical management and sequestrants. But I think until we get more info it may be premature to assume one way or the other yet. We'll definitely get many sets of eyes on your thread and do all we can to help you.

To increase CYA via granular stabilizer, place the required amount as calculated by the Poolmath calculator into a white sock and place in the poolside skimmer basket. For those concerned about suction flow to the pump, suspending the sock near a return jet or from a floating device will also suffice. Best never to allow undissolved granules to rest directly against the pool surface. Squeeze the sock periodically to help it dissipate. Once dissolved, consider your CYA adjusted to that programmed (target) level. CYA test readings should show a rise in 24-48 hours, however some pools may experience a longer delay to fully register. Best to confirm final CYA in about 5-7 days before adding any more stabilizer/conditioner.

 

[maxjar10]

Hi Tex,

Thanks for the advice. I went to the pool store and had them run tests. There was no iron or copper in the water. The results were:

FC: 0
PH: 7.6
CH: 275
CYA: 40
TA: 100
Iron: 0
Copper: 0
Phosphates: 100

The strangest part was the CYA supposedly being 40ppm. The only way 40ppm CYA would have built up is from the 8oz total of dichlor that had been added and I tested these at 0 (I tested again once I went home). So, I think their CYA test went wrong (no other way I can think that CYA would have been in the water). I also have a CH: of 350 and not 275 as they recorded.

In any event, this evening at around 6PM I put 27oz of CYA in and 35oz of 8.25% bleach. This should yield:
FC: 3
CYA: 30 (I know that some CYA was in because of the dichlor so I started it at 5).

The CYA is in a sock in the skimmer and I will squeeze it again before sleep. I'll test in the morning but I know that the CYA likely won't record fully yet. I'll add more FC and acid as necessary.

Thanks again for the help!