Polyquat or not ?

[ChuckD]

This may be a testament to how a Cl shock will kill your Poly: I closed last fall with a double dose (half gal. in 20K of water) and then a shock, and while I can see the bottom in the four foot end, the deep end is dense green. I also use only a mesh leaf net as a cover.

[chem geek]

Note this post where a chemist at Buckman Laboratories gives the recommended closing procedure which shocks with chlorine first, then lets the chlorine level drop before adding PolyQuat.

Richard

[CarlD]

OK, here's how I do it and EVERY season I open to clear water. I take into account that the PolyQuat in large amounts causes the FC level to collapse. But I don't do this until the water is AT MOST in the low 60's, colder is better.

1) shock the pool

2) Add 1 quart of polyquat.

3) Wait 24 hours for the chlorine to drop.

4) Shock it up again.

5) Close

Yes, it's really all it takes.

[haze_1956]

I found it interesting that the CYA was at 0

Wondering if the algae ate it last fall and then froze and dropped to the bottom.

[CarlD]

My CYA dropped from about 40 to 25 over the winter...but I had lot of dilution from rain and snowmelt

[chem geek]

Many people find their CYA level dropping to 0 over the winter. Though it is possible that algae eat it for food, what IS known is that there are anaerobic bacteria that normally live in soil that definitely consume CYA. It is very possible that at least for pools where the FC gets to 0 that these bacteria consume the CYA. If they do, then they produce ammonia as a by-product which would mean needing LOTS of chlorine to open a pool.

Some users report the CYA dropping over the winter even maintaining chlorine levels. This happened to me this winter going from 20 to 10 (approximately) and I had no dilution (I have an automated opaque pool cover), but in past winter's I hadn't seen this and I've maintained chlorine levels every winter.

Richard

[haze_1956]

Alk is down too. 120 to 70.

Lot of start up this year !! LOL

Hate it when an experiment turns around and bites me in the wallet.



I'll use poly this coming Fall and see what I find in Spring 2008.

[ChuckD]

Note this post where a chemist at Buckman Laboratories gives the recommended closing procedure which shocks with chlorine first, then lets the chlorine level drop before adding PolyQuat.

Richard

Right, Richard, very familiar with that post and knew about the nullifying effects at higher concentrations. Thanks for the info. My pool's not at my primary residence tho, so I didn't have time to wait for Cl levels to drop. Just the weekend.

But I have a follow-up to that referring to your comment about the 'heavy molecular weight' of the Polyquat and another, as yet unresolved controversy concerning it. Some here say that a DE filteration system will filter out the Polyquat, I remain unconvinced. Do you think, given its higher weight this is a concern? I don't have a bypass, or circulate-only mode on my Hayward EC-65, so it's a real concern for me.

[chem geek]

I've sent an E-mail to my contact at Buckman Laboratories that makes PolyQuat. I'll let you know what they say but I suspect that the PolyQuat polymer, though long-chain and viscous, is not 5 microns in size and that's about the smallest that a DE filter can capture (I believe -- 10 microns is what usually is quoted for "typical"). I'll let you know what I find out.

Richard

[chem geek]

Here's the response I got from Dr. McNeel (with some definition comments of mine in brackets):

The molecular weight of PolyQuat is in the low thousands (~3000-5000 daltons [each polymer unit has a molecular weight of 253.17 as seen in this post so the polymer has roughly 12-20 units and each unit is very roughly 0.01 microns in length], so an UNCHARGED filter is not going to remove it from solution, no matter how small its effective pore size may be. However, an anionic [negatively charged] surface (such as an cation exchange resin) will definitely remove PolyQuat from the water. In fact, PolyQuat will bind so tightly to a polystyrene-based strong-cation exchange resin that even concentrated hydrochloric acid will not displace it from the resin.

Diatomaceous earth and other silica-based structures will have a net cationic [positive] charge on the surface at neutral or acidic pH levels and hence will not tend to bind PolyQuat too much; however, if the pH is sufficiently high, the surface can become anionic [negative]. I don't think that the pH levels normally found in pools will be sufficiently high to be a problem for PolyQuat. Studies have been carried out in the past with sand filters (another silica-based filter medium), and PolyQuat loss on the filter medium was not found to be a problem.

It is interesting to note that if one were to use a water softener (cationic exchange resin) to try and reduce Calcium Hardness, one had better not have any residual PolyQuat in their water or else their water softener will essentially be ruined.

Richard