Scale

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jimwt

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May 3, 2009
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West Texas
First time poster: I have a scale problem in my spa(what's the difference between a hot tub and a spa?). The scale which is dirty looking is probably CaCO3 with embedded sand.

Water Chem: pH-8.2, FC-2.5, CC-<0.5, TA-180, CH-250-300, CYA-0

A review of posts in this forum suggests that the best practical solution to scale removal is to drain and acid treat over the no-drain Jack Magic treatment. Correct?
Would it be worthwhile to lower pH and brush vigorusly?

I know the pH is high coupled with the Ca has probably led to the scale formation. Our water is very hard. The spa has been drained 2X and refilled, and the pH will bump up from 7.9 to 8.2 or more on its own. If I acid treat, do I need to keep the pH lower with acid on refilling? Also, the CSI is about +1.0. The water is very clear.

I'd like to hear from the experts on this.

Thanks and I've learned a lot from this site.
JImwt
 
Jim,

I don't have a spa/hot tub (I don't know the difference, either) so I'm not much help on treatment.

Once you get it fixed, you must keep your pH in the low to mid 7's to prevent reoccurence. Others will be along soon to offer advice on fixing the issue.

Welcome to the forum.
 
I'm no expert (but I play one on the Internet...)
jimwt said:
(what's the difference between a hot tub and a spa?)
Click to expand...
Pretentiousness. :-D When you turn your place into a B&B you get to charge more for a spa than a hot tub. :mrgreen:

Actually I think the difference is a spa has jets. I did stay in a fairly "rustic" place once that had a hot tub with no jets. But most people use the terms interchangeably.

Sorry I can't help with treatment either. Long term like duraleigh says, keep the pH under control, and lowering your TA will help.

On an unrelated topic, I see CYA 0... keeping 20-30ppm is helpful even in a covered spa, I've found Nitro's Approach to Water Maintenance works very well.
--paulr
 
If you had a water source that was not high in TA and CH, then you could use that along with lower pH (say, 7.0) to help dissolve the scale buildup. However, since you don't have that kind of water source, you'll have to lower the TA quite a bit via the Lower Your Alkalinity procedure. It should go fairly fast since aeration in a spa is easy to achieve. Get your TA down to 60 ppm and keep the pH at 7.0 and lightly brush the areas that have scale. If you can somewhat lower the water temp down to 80F or so, that will also help (i.e. don't heat the spa as much). Though the saturation index will be negative during this time, it won't be for so long as to cause problems and the pH won't get too low (i.e. you will avoid any metal corrosion).

Let us know how this works. If it doesn't, then a mild acid solution can be used to remove the scale, but the above procedure is better as it is less drastic and will help clear areas you can't get to (i.e. pipes, heat exchanger, etc.). There are also scale removal products that can be used, but try the above procedure first. Also, you'll want to get your TA lowered anyway so the above procedure makes that happen.

After you have successfully removed the scale, you can follow Nitro's guide that Paul linked to.

Richard
 
The best way to remove the scale is to drain the spa and do a manual acid wash. There is some skill involved in removing the scale and not damaging the plaster. If you don't feel completely confident you might be better of having the acid wash done by a professional.

The scale is being caused by your high TA level. In a spa, high TA quickly results in high PH. The combination of high PH and high TA and practically any CH in the water, will almost invariably cause scaling. You need to lower the TA, and will probably need to do that again after each refill. You can read about how to lower TA in a spa here.
 
Just FYI. The reason for the seemingly different advice is that I was presuming that your scale problem most recently occurred. When that happens, lowering the saturation index can often redissolve newly formed scale fairly easily, especially on non-plaster surfaces (i.e. in most spas). However, if the scale has been there for a while, then what Jason proposes in terms of a manual acid wash is better, indeed required, since the scale won't dissolve so readily if it's had more time to adhere and thicken to surfaces.
 
Thanks for all your inputs. At least now I have a plan which is try the aeration technique to lower TA and acid for pH. Most of the scale is new but some has been present for nearly a year. If aeration with lower pH doesn't work, I'll proceed to the acid wash method(hate to think about it).

Thanks again and I'll post results. By the way water temp. is 83 deg. F. To lower any more would require ice. It's hot here in W. Tex.

Jimwt
 
Well, I lowered the TA to 50-60 using the aeration method with acid over the weekend. Worked well. pH would drop to the 6.8 and bounce back to 7.2-7.6 in a few minutes with aeration. Took more acid than calculated to get the TA down. With just the main spa pump running, pH kept rising after acid dump. Getting too much aeration, I suppose. Last evening pH was 7.2, this a.m., 7.7. Put in 2 oz. HCl, pH down to 6.8. Turned off pump. Have been brushing all along since Sat., no apparent help with scale. Still brushing with pump off and low pH. Question-How long should I keep brushing?

Should I try some no drain product? If so, can someone recommend something.

OR, should I proceed to an acid wash now?

Thanks,
Jimwt
 
If it doesn't redissolve quickly, within a day or two, then it's probably not going to (probably because it's too old so built up too much and too strongly) or will take a lot longer (weeks). The mild acid wash that Jason recommended would definitely dissolve the scale so would be the next thing to do. There are scale removal products, but that's extra cost for something that mild acid will take care of.
 

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jimwt said:
what's the difference between a hot tub and a spa?
Click to expand...
Since your scale issues have pretty much been addresed I thought I would answer this. Traditionally a hot tub is a wooden tub (often ceder) held together like a barrel with metal rings and without jets but often with some type of filtration and circulation system and often heated with a wood burning heater or an electric immersion heater while a spa is a vessel that is not wooden and has jets and pluming similar to a small pool . However, the distinction has become blurred since there are very few REAL hot tub manufacturers around these days so the terms are pretty much used interchangeably.
 
Update: I had my tub acid washed last Mon. It looks great. Been working on water since then: pH-7.8, TA-75, FC-8.5(after shock to 10+), CC-1.5, TC-10, CYA-0, Temp-82 deg F. Should I be concerned about the CC?

Plan to add some CYA, shooting for 30.

Thanks again,
Jim wt
 
Update: As noted earlier, the acid wash worked well as did lowering the TA with acid and using aeration to raise pH while keeping the TA low.
Current analysis: pH-7.4-8.2*, TA-100, FC-4, CC-Tr, CH-400-500, CYA-28, Temp-83
*Problem with keeping pH in range. Can add acid and lower it to 7.4, but it will increase to 8.2 within 24 hrs. I wonder if I'm getting too much aeration from the one return jet causing the pH increase. The jet breaks the surface with a fair amount of force. Should I adjust it to emit the return stream below the surface?
The pump runs 24/7.

Also, don't understand why the spa water has a CH of 400-500, and the pool is 300. Both have the same water source which is city water. I check the city water at 260-300 CH. The city water is hard with a Ca/Mg hardness level of 547 ppm according to to their official report. Perhaps it's my test techniques. I do have problems dicerning when exactly does the sample turn blue.
Jimwt
 
I would suggest bringing down TA another 20-30 points, to try to reduce the rate of pH rise. Less surface agitation would also help.

The slow pace of the CH test can make it hard to tell when a color change is taking place, but I wouldn't expect it to make a difference of over 100ppm. Are the spa and pool plumbed separately, or do they run off the same filter and pump? If they mix, you'd think the CH readings would line up; if they (mostly) don't then I could see the spa's CH being different from the pool's.
--paulr
 
jimwt said:
Update: As noted earlier, the acid wash worked well as did lowering the TA with acid and using aeration to raise pH while keeping the TA low.
Current analysis: pH-7.4-8.2*, TA-100, FC-4, CC-Tr, CH-400-500, CYA-28, Temp-83
*Problem with keeping pH in range. Can add acid and lower it to 7.4, but it will increase to 8.2 within 24 hrs. I wonder if I'm getting too much aeration from the one return jet causing the pH increase. The jet breaks the surface with a fair amount of force. Should I adjust it to emit the return stream below the surface?
The pump runs 24/7.

Also, don't understand why the spa water has a CH of 400-500, and the pool is 300. Both have the same water source which is city water. I check the city water at 260-300 CH. The city water is hard with a Ca/Mg hardness level of 547 ppm according to to their official report. Perhaps it's my test techniques. I do have problems dicerning when exactly does the sample turn blue.
Jimwt
Click to expand...

Does your spa share the filtering system/water with the pool? If so, there is probably no point in lowering just the spa TA/PH as when in spillover mode, the spa water will just be replaced with pool water. Although from your CH statement it sounds as though they may be separate.

Also, be aware that PH will usually rise in a spa when the jets are going. This is especially true with high TA but happens even in my spa when TA is 80 ppm. One thing I will do after a long spa run is to replace the water with pool water in spillover mode to avoid scaling. Also, I have measured my PH rise and from 7.6, it can hit 8.0 in less than an hour with 6 jets running. So it is nearly impossible to keep the PH low but it can be managed by either spillover or treatment after usage.
 
The pool and spa plumbing is totally separate and are not in the same location.
I will redirect the return jet to reduce agitation after lowering the TA with acid; then see if the pH stays under better control.

Thanks for the inputs.

Jimwt
 
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