Should I Just Start Over?

[GaTub]

We are two-week new owners of a Sundance Hartford (rated at 470 gal) with Clear-ray UV, no ozonator. I posted the comedy of errors I've gone through with the water chemistry up to now in the main Hot Tubs & Spas section. Figure I'll continue on here. Summary to date:

• New tub was filled by the tech, then he added a 32 oz bottle of Brilliance pH true (dipotassium phosphate / monosodium phosphate) and maybe about 2 tbs of dichlor. He put a N2 cartridge in the filter housing.
  
• His instructions were to add about 1 tbs of MPS before using the tub and 1-1/2 tbs of dichlor once per week. Unfortunately he did not say that the MPS and N2 cartridge work together to keep the water clean, and that addition of the MPS is very important.
  
• I read the instructions that came with the tub and it said to maintain at least 1 ppm FC if equipped with UV. My wife and I soaked in the tub that evening and once each day for the first several days. The test strip kept on reading 0 FC in the morning so I added 1-1/2 tbs dichlor (in addition to the MPS before soaking.) Everything seemed OK but the 0 FC readings bothered me.
  
• Then the really good part- I got called away on business for most of last week. Just before I left we found our golden lab in the tub taking a swim, but I didn't realize how big an issue it was. Also my wife and friend soaked in the tub several times while I was gone and no chemicals were added. When I returned the water was hazy and greenish. Thats when I first posted looking for advice, and began studying up. Nobody (including the dog!) has used the tub since.
  
• I added dichlor, then MPS over the weekend and the water stayed hazy. FC readings using the strips kept on dropping to 0 overnight, so for the past three days I hit it pretty hard with the dichlor and it gradually cleared. I also added some pH-Up (soda ash) a couple of days ago because the ph readings using the strips began dropping quickly.
  
• The K-2006 kit that I ordered arrived last night and I just finished testing.
  

FC: 6 ppm (reads maybe around 3 ppm using the strip)

CC: around 1 ppm (may be residual MPS?)

pH: 7.0 (bottom of the scale, the strip reading also shows low pH)

base demand: 35 drops (off the chart!)

TA: 120 ppm

Ca Hardness: <40

CYA: approx 100 (did this twice, got 95 the first time, and well over 100 the second time diluted with tap water per the kit instructions)

Now for the questions-

• I still do not understand why the FC kept on dropping to 0 overnight the first few days after the tub was filled. We used it but not very heavily. Of course I was relying on the strips, and maybe 0 wasn't really 0. Any thoughts?
  
• Adding all the dichlor looks like a rookie mistake. I totaled it up and we've put in maybe 18 tbs, figure 9 oz by volume. According to the pool calculator this would be 85 ppm total which is way over twice the amount recommended in the Spa Guru dichlor/bleach method startup. Would this be enough to take the CYA up as high as my reading?
  
• Why is the pH dropping? The dealer seemed to know this would happen because he included pH-up in my starter chemicals and no pH-down. The pH drop became noticable on the strips when I stopped adding MPS and hit it hard with the dichlor. But the base demand reading seems pretty crazy. If the table is right it would take a lot of soda ash to get it back in the center of the range again.
  
• Are there any issues with the phosphate-based buffer other than my pH drop?
  

Is there any quick fix or should I just dump the water and start over again? The tub itself looks great- the walls are perfectly clean even at the waterline, there is nothing floating on top, and no particulates in the water that I can see. So it wouldn't be hard to do. The guys at the dealer seem to know what to do but they don't explain things in real "chemistry" terms like the experts here. So they haven't been that helpful since things got way out.

By the way, I've learned a ton here over the past few days!!!

[chem geek]

New spas are usually wet-tested and if the pipes are not thoroughly dried then biofilms can form. They can also have grease. So one really needs to decontaminate a new spa, preferably with Spa System Flush (you can do that on your next drain/refill if you want). So having a high chlorine demand on a first fill is not at all uncommon if you don't do this. Of course, test strips can bleach out at high chlorine levels so that is another possibility.

For every 10 ppm Free Chlorine (FC) added by Dichlor, it also increases Cyanuric Acid (CYA) by 9 ppm so your adding 85 ppm FC would increase CYA by 77 ppm. Perhaps you added somewhat more Dichlor than you thought, but in any event continued use of Dichlor will increase your CYA level making the chlorine less effective.

Dichlor is net acidic when accounting for chlorine usage/consumption. MPS is also acidic. So it is not surprising that you are needing to add pH Up. Your higher Total Alkalinity (TA) level is helping to keep the pH from dropping even more -- if you were to use aeration jets the pH would not drop as much. However, rather than using a phosphate buffer, why don't you use bleach which is close to pH neutral when accounting for chlorine usage/consumption. If you do that, you'll need to lower your TA level with acid and aeration first and should then add 50 ppm Borates (a pH buffer like phosphate buffers, but doesn't promote algae or bacterial growth).

[GaTub]

The correct answer is/was YES.

I went by the dealer with a water sample and he confirmed all my test results. Then we got in a bit of a debate. I told him the high CYA was undoubtedly due to all the dichlor I added. He disagreed, saying that the dichlor that he gave me was not stabilized, it will not increase CYA, and that the buffer was probably affecting the test. Anyway I decided to go ahead and change the water. Nothing fancy- I just drained, cleaned the filters, and refilled using the same phosphate-based buffer and the N2 cartridge. It only took a few hours. I primed with 3 tbs of dichlor and let it sit overnight.

I just checked the chemistry- what a difference!

fc - 13 ppm

cc - .5 ppm

pH - 7.6

TA - 160

Hardness <20

CYA <30

When the tub was first filled brand new the fc dropped to almost 0 by the next morning, so this is a big change in itself. This time, after 16 hours it has barely dropped at all. There must have been something in the tub to start with that affected the balance. Everything else is right in range and the CYA is lower than the K-2006 kit can test for.

Lessons learned:

Don't blindly trust the local dealer for chemistry advice.

If the balance goes way out after the first day then plan on draining and refilling to remove any deposits that may be in there from the factory.

Don't let the dog go swimming!

Be careful with dichlor additions. I now have a bottle of chlorox sitting alongside my other chemicals.

I am going to try using my version of the N2 system because I think it will be easier for my wife to manage while I am out of town (I travel very frequently). But now I know what to watch for, and if it doesn't work out I will try the posted dichlor/bleach method next.

[Fatlip]

If I were you, I would use the dichlor/bleach method and be done with it. Also use the borcic acid and you numbers will not change much, if at all. This method is very cheap to use and easy for the wife to do. My spa only uses 3oz a day bleach with just me using 1 time a day, but is only 235 gal, Hotsprings Jetsetter.

Hope this helps,

Rick

[waterbear]

If I were you I would change dealers since dichlor is a chemical made from chlorine and CYA and for every 10 ppm FC added it also adds 9 ppm CYA that stays in the water and builds up as the chlorine is neutralized. Dichlor is by definition a stabilized chlorine or a chlorinated isocyanurate. Perhaps you might want to print this post and show it to the dealer to whom I suggest learn a bit more about the chemicals he is selling since he obviously does not know much at all!

If he gave you a non stabilized granular chlorine it was either calcuim hypochlorite which raises calcium hardness (and to the best of my knowledge is only sold by Arch chemical under the HTH and possibly a few other of their numerous brands) or lithium hypochlorite, which is extremely expensive!

If he gave you dichlor it is stabilized chlorine and causes CYA to rise. PERIOD!

AS far as what to use, you have to decide if you are going to do dichlor/bleach, continue with the silver/MPS (and if you do follow the instructions), or give three step bromine a go (good choice for a tub hat does not get constant use and the most 'forgiving; of the three methods if you ignore the tub for a few days to a week).

[GaTub]

I have the chemistry down now and agree 100% on the the dichlor and CYA. But I wasn't going to convince him no matter what- think I may have hurt his pride by pushing it as far as I did.

On the other hand the showroom is literally only 2 miles away, and they are the only spa dealer for at least 100 miles in any direction. I have no problems with the deal on the spa or the work that he did to install it. And all-in-all he really is a nice guy. So no use making an enemy over what amounts to a bit of ignorance especially since I don't need his chemistry "expertise".

Like I said I am going to give the N2 system a shot, and if it doesn't work out I'll try the dichlor/bleach method next. If I go this way I will probably have to order boric acid off the net since the supply of spa chemicals is a bit limited at the local dealer. But no problem doing that.

My fc hasn't dropped at all today- still stuck at 13 ppm. Now thats a different sort of problem to have, but a welcome one.

[chem geek]

Since you said you are using a phosphate buffer, I'm curious if that initially clouded the water since it would normally lower the Calcium Hardness (CH) level forming calcium phosphate, though if your fill water is very low in CH then you may not have had any cloudiness. Also, let us know if you have any problems with foaming since the CH will be low.

[GaTub]

The water is perfectly sparkly clear and absolutely no foaming so far even with all the air jets wide open. But we haven't used it yet since the refill. I'll let you know how it goes as things settle in.

[GaTub]

The fill capacity of the tub is 390 gallons. Not sure where I got the 470 from (too many numbers running around in my head!) But that accounts for the higher than expected fc when I added the 2 tbs dichlor. It is dropping very slowly, but eventually should get in range, right?

I just made up a little notebook with all of the assorted conversions, and suggested add amounts based on my 390 gallons. And I will log in usage, chem adds and test readings for a while until I get a good feel for what I need to do to keep the water healthy.

My plan is to follow the N2 instructions, and shock fc to 10 ppm or so once each week for a while regardless of whether it looks "needed". I am hoping/thinking that the fc depletion rate after the shock should give me an indication of the health of the tub. And then I will adjust MPS adds if needed based on how we are actually using it- but never go below the recommended adds in the N2 instructions.

The N2 instrutions don't say anything about it, but is there any reason not to use Chlorox for fc shocks instead of dichlor once I get to the 30 CYA level? I don't want to get CYA out of control again! And this should also reduce the tendency for pH to drop. According to the pool calculator it will take about a cup (8 oz) to bring cc from 0 to 10 ppm in my 390 gal spa. Does this sound about right? Getting tired of making mistakes so a double check would be appreciated.

[waterbear]

Once it is in your water chlorine is chlorine. It all becomes hypochlorous acid and sodium hypochlorite.

[GaTub]

We are back to using the tub, with a couple of people soaking at least an hour or so each day. I am following the N2 system to the letter and the water is sparkly clear, and there is no foaming. According to the strips the fc is fully depleted and we are now relying on the MPS and the cartridge, along with the UV.

When I tested fc last night using the K-2006 kit a light pink color developed in about 10 seconds or so. I could knock it out by adding about 14 drops R-0871 but then it came back again after a few seconds. I assume that this is due to the MPS, and since everything looks good I will use this as my baseline. I know my test chemicals and method are fine because I tested my city tap water and the response was normal with a sharp titration endpoint, showing a trace of fc (<1 ppm) which is exactly what I would expect.

Testing the water has actually gotten to be fun- reminds me of my college organic chem labs years ago!

[chem geek]

MPS will react with FAS-DPD drops so if you see any pink at all during the FC test (which can be from chlorine or perhaps a small amount of MPS bleed-through), then you could use a lot of R-0871 drops. Basically, when there is MPS, the FC portion of the K-2006 test is pretty useless. After adding the DPD powder, just add the R-0003 potassium iodide which will turn the sample pink/red if chlorine or bromine or MPS is present and then the FAS-DPD drops will be measuring the sum of chlorine, bromine and MPS together. There is an MPS interference remover you can get in the Taylor K-2042 test kit, but with your MPS test strips that isn't necessary.

[GaTub]

Almost a month since the water change and everything is good- nice clear water, no deposits, slime, or foam, and TA and pH are stable.

A followup question for the chem experts- how much residual MPS is needed in order for the N2 system to be effective at disinfecting? I am adding some whenever the level gets to "low" on the N2 test strip and that seems to be working. But if it gets to 0 will the cartridge continue to work for some time- hours, days? I know that fc should never go to 0 when relying on chlorine alone, but the N2 instructions do not really say anything about maintaining residual MPS.

I am hitting it with some chlorox once per week and also added some the few times that the tub has been very heavily used. That also seems to be working good.