Aeration set up

Rangeball

Well-known member
May 25, 2007
785
#1
As I've posted before, we have high TA fill water. I'm continually battling PH increase, and normal methods of aeration take days to move PH up much after reducing and good aerators like rain and lot's of screaming kids doing cannon balls are never around when you need them :)

I've been giving serious thought to using an air compressor rigged up to continually add air to the deep end of the pool, using a long hose and some type of end that would encourage formation of small bubbles. I'm hesitant because my air compressor tank is shot (Old one my grandpa gave to me and the tank is rusted through), new air compressors are expensive and I'd have to borrow my brother's long term, possibly. Plus, the compressor turning on and off throughout the night might disturb the peace :)

I've been wondering about using something like this-

http://www.harborfreight.com/cpi/ctaf/d ... mber=40057

Portable air tank. 10 gallon size with a max of 200 psi. I don't know how to calculate how many cubic feet of air it would hold, or how long it would last once set up and the valve opened. Anyone have any ideas?

Seems like I'm grilling all summer long on one tank of LP, which is a smaller tank size. I've got my fingers crossed that this 10 gallon air tank would trickle air for several hours, at least.

Anyone have any idea?
 

piku

LifeTime Supporter
Mar 12, 2008
259
Hatfield, PA
#2
Firstly, I would not recommend putting 200 psi into anything harbor freight sells :p But that aside, the equation is V2/V1 = (P1/P2)^0.71 for the adiabatic expansion of air. Your will not be able to use any air that is under the pressure required to deliver the air to the bottom of hte deep end (I found it is 18 psi at 8 ft). Also the equation calls for absolute pressure rather than gauge pressure so just add 14.7 for pressure at sea level.

V2/V1 = (P1/P2)^0.71
V2 = (P1/P2)^0.71 x V1
V2 = (214.7/32.7)^.71 x 1.33 cu.ft.
V2 = 3.8 cu ft.

I'm sure I'm missing something there like you might have to remove 1.33 cu ft from the equation since you can't take the air out and create a vacuum. But yeah, around 3 cu ft and I can't imagine that taking you that far unless you make VERY tiny bubbles slowly. The article I was reading suggests that you can only barely inflate 1 tire with it. I would look to adding air through the pool plumbing somehow.
 

sevver

Well-known member
Mar 27, 2007
477
Morris, IL
#3
It won't cut it. I ran a thirty gallon compressor on full bore running the compressor motor non stop for three days to lower mine. Never shutting off, it ran non stop. I would not borrow anyones compressor without understanding that it may get killed doing this. They are not designed to run like that. I just so happened to not care... I rigged it into the plumbing of the pool right before the return. I now use that port for a water jet, which honestly lowers the TA faster in my honest opinion. Can you post pics of your plumbing.
 

Rangeball

Well-known member
May 25, 2007
785
#4
So, of all the compressed air that tank will hold, only a bit over 3 cubic feet will be expelled into an 8' deep end, and the balance will remain in the tank due to a pressure equilibrium?

(don't ask me how many times I read your post to get this far... :) )

I was thinking deep end so that the bubbles would have more time to draw in the carbon dioxide. What if I put it in my 3' shallow end?

I could rig up a fitting in my my return from the filter that I could couple the air hose into and inject the air into my return line, which would give it about 37' of run before it hits the pool. Would that simulate a very deep end, yet since it's at essentially the same level as the tank I'd get the majority of the compressed air out?
 

Rangeball

Well-known member
May 25, 2007
785
#5
sevver said:
It won't cut it. I ran a thirty gallon compressor on full bore running the compressor motor non stop for three days to lower mine. Never shutting off, it ran non stop. I would not borrow anyones compressor without understanding that it may get killed doing this. They are not designed to run like that. I just so happened to not care... I rigged it into the plumbing of the pool right before the return. I now use that port for a water jet, which honestly lowers the TA faster in my honest opinion. Can you post pics of your plumbing.
I don't have one handy. But I have about 4' of 1.5" ID hose running from the filter to the fitting coming out of my pad, then 1.5" line running under the pad about 30' back to my 1 return.

What do you mean by a "water jet"?
 

mas985

TFP Expert
LifeTime Supporter
May 3, 2007
12,181
Pleasanton, CA
#7
I'm curious if aeration would be counter productive for high TA fill water. Aeration will raise PH but it will also increase evaporation which would then need to be replaced with high TA fill water so it could be a reduced benefit.

I struggle with the same problem but gave up on reducing TA because as soon as I lowered my TA to 70 or so, it was back up to 90 again after only a few weeks. With high TA fill water and high evaporation, it doesn't take long for TA to climb back up again.

My solution for keeping PH in check was to install an acid dispensor system as shown here. This has worked pretty well and keeps my TA in check as well.
 

Rangeball

Well-known member
May 25, 2007
785
#8
JasonLion said:
Check out the picture link in this post for a very effective aerator design.
Thanks Jason. I built something similar, but it doesn't churn the water near that hard. Basically I just used 1.5" PVC that I angled up from my return so the return flow flew up then down into the pool.

I need to re-study that pic and go back the the drawing board. I'd love for a water solution for aeration to work.
 

Rangeball

Well-known member
May 25, 2007
785
#9
mas985 said:
I'm curious if aeration would be counter productive for high TA fill water. Aeration will raise PH but it will also increase evaporation which would then need to be replaced with high TA fill water so it could be a reduced benefit.

I struggle with the same problem but gave up on reducing TA because as soon as I lowered my TA to 70 or so, it was back up to 90 again after only a few weeks. With high TA fill water and high evaporation, it doesn't take long for TA to climb back up again.

My solution for keeping PH in check was to install an acid dispensor system as shown here. This has worked pretty well and keeps my TA in check as well.
I don't have SWG, so my rise isn't as rapid as yours might be, but your points are well taken.

My main concern with a higher PH is that it reduces chlorine's effectiveness. I remember way back at PF Ben said if PH wanted to be high, don't fight it, and I think just run a higher bleach level. Perhaps the algae control the borates provide would make this all a moot point and I should just add them and knock PH down as needed?
 

mas985

TFP Expert
LifeTime Supporter
May 3, 2007
12,181
Pleasanton, CA
#10
Rangeball said:
Perhaps the algae control the borates provide would make this all a moot point and I should just add them and knock PH down as needed?
Given your fill water TA, that may be your best option but it is probably worth a try to see if you can keep the TA down. You might have less evaporation than I do so you might be able to keep down to a reasonable level but I suspect it will be hard to do.
 

chem geek

TFP Expert
LifeTime Supporter
Mar 28, 2007
12,082
San Rafael, CA USA
#11
Rangeball said:
My main concern with a higher PH is that it reduces chlorine's effectiveness. I remember way back at PF Ben said if PH wanted to be high, don't fight it, and I think just run a higher bleach level. Perhaps the algae control the borates provide would make this all a moot point and I should just add them and knock PH down as needed?
You do not need to be concerned that much about chlorine's reduced effectiveness at higher pH. As you can see from the graphs in this post, the traditional industry graph on the left showing a 50% reduction in chlorine effectiveness from a pH of 7.5 to 8.0 isn't what happens in the presence of Cyanuric Acid (CYA) shown in the graph on the right. The disinfecting and oxidizing chlorine (hypochlorous acid) concentration only drops by around 15% when CYA is present. This is because CYA is a hypochlorous acid buffer and resists changes to its concentration from changes in pH or other factors.

So if your pH gets to 8.0, you can just increase your FC level by 15% to get equivalent disinfection/oxidation. The main issue with higher pH would be scaling if your TA and CH were also high enough for that to occur.

Richard
 

Rangeball

Well-known member
May 25, 2007
785
#12
Mark, I got my TA down to 80ish last year, and it was back up to 120-30 by years end.

Richard, interesting, I had always understood chlorine was weaker at higher PH. Well, I guess technically it is, but not by as much as I thought.

I also just had an interesting observance that seemed to back up my previous understanding. When my PH was up around 7.8, I was losing 2 ppm FC at a CYA of 50 pm with no CC and crystal clear sparkling water. When I dropped my PH to 7.2, FC usage went down to 1 ppm. Could be a fluke, I'll monitor it and see.

I don't use a calcium source of chlorine, haven't for 3 years. With a vinyl liner IG pool, I don't even test calcium, and won't unless I start to notice foaming.
 

chem geek

TFP Expert
LifeTime Supporter
Mar 28, 2007
12,082
San Rafael, CA USA
#13
It is true that hypochlorite ion breaks down in sunlight at a rate over 6 times higher than that of hypochlorous acid. With your numbers and assuming an FC of 5 ppm, at a pH of 7.2 the hypochlorous acid is 0.050 while the hypochlorite ion is 0.027 but at a pH of 7.8 the hypochlorous acid is 0.039 while the hypochlorite ion 0.082 so having a higher FC loss at the higher pH makes sense. Though the rate of disinfection and oxidation only drops a relatively small amount, the rate of FC loss increases quite a lot.

Richard
 

Rangeball

Well-known member
May 25, 2007
785
#15
chem geek said:
It is true that hypochlorite ion breaks down in sunlight at a rate over 6 times higher than that of hypochlorous acid. With your numbers and assuming an FC of 5 ppm, at a pH of 7.2 the hypochlorous acid is 0.050 while the hypochlorite ion is 0.027 but at a pH of 7.8 the hypochlorous acid is 0.039 while the hypochlorite ion 0.082 so having a higher FC loss at the higher pH makes sense. Though the rate of disinfection and oxidation only drops a relatively small amount, the rate of FC loss increases quite a lot.

Richard
Learn something new every day... :)

Thanks.
 

Anemone

LifeTime Supporter
Jul 9, 2007
48
Northeastern Maryland
#18
This is what I use http://store.namcopoolstore.com/web31348.html on my inground pool. I picked it up at a local pool store and it screws right into a return. It is also very adjustable. It can be moved to many positions and the force of the spray is adjustable (from a few inches to having it shoot all the way across the pool).

I think I paid $20 and it was really easy to set up. It is not real pretty but it the falling water does sound nice. :mrgreen:

If anyone would like pics of it in action, just ask.
 

Rangeball

Well-known member
May 25, 2007
785
#19
Anemone said:
This is what I use http://store.namcopoolstore.com/web31348.html on my inground pool. I picked it up at a local pool store and it screws right into a return. It is also very adjustable. It can be moved to many positions and the force of the spray is adjustable (from a few inches to having it shoot all the way across the pool).

I think I paid $20 and it was really easy to set up. It is not real pretty but it the falling water does sound nice. :mrgreen:

If anyone would like pics of it in action, just ask.
I'd love to see a pic of it in action, pointed down at the water. Thanks :)