Each Spring Opening I Have Rough Pitted Marcite in ONLY the Spa

[mmcwhorter]

I have noticed over the last three years that our "raised overflow waterfall spa" surface on both seats and vertical walls is very pitted when we pull the cover off in Spring. The rest of the pool is smooth. When closing in late Fall I take good care to balance the pool & spa.....and then shock. The water is very clear in the Spring. When spa water was tested at the opening I saw the pH was off the charts, deep purple....the FC was 0 of course, and the TA was about 40, CYA around 20. Calcium was at 400. Before use, I have added acid and CL, and have it around 7.2 to start and 3.0 FC ppm now. When we went in the Spa for the first time in early Spring...it was worse than sitting on 20 grid sandpaper. Mama wasn't too happy. This is at least the third year of this situation...so I thought I'd reach out to the Forum. Last two years I used a Lava stone to flatten out the rough peaks. I wonder if wet sanding with a fine grid 220+ will work, as the Lava Stone is ground up quickly.

So, I am asking: is there something I should do before closing each year? During the winter? I certainly carefully balance the pool and spa per TFP recommendations before closing, and just for the heck of it usually take the FC up to about 20 ppm using 73% Cal-Hypo the day the cover goes on, before shutting off the pump, letting it run a few hours, and later doing all the closing steps required. Would it be a good idea to drain the spa and perform an acid wash? That would be easy....but It would worry me to do that each and every year. If yes, should I use 25% liquid acid/water, or perhaps 50% liquid acid/water (using the 31 BAUM muriatic acid)? Should I periodically add "heavily diluted" acid into the spa during the winter to keep the pH from being super high?

Ready to break out the wet sander block!

Puzzled. Thanks!

 

[RDspaguy]

Are your pool readings the same? I am no chemical expert, but it sounds to me like scale, not pitted marcite, resulting from high ph and calcium.
@Jimrahbe , @ajw22 , your thoughts?

 

[mmcwhorter]

When I close around Haloween pH is around 7.2 and Calcium is admittedly on the higher side the last year or two, ranging around 375-400... that may be the problem. When I open in mid-March pH is off the charts purple (who knows???) ....and Calcium about the same. I was thinking the same as you suggest and might try next winter to set up a low dose acid added, maybe using a funnel and a tube running int he spa under the cover....every week or so put in a few ounces of diluted Muriatic, say 4 oz in one quart. Thank you for the reply.

 

[mmcwhorter]

Another idea, if it is the calcuim...maybe before closing/covering...drain and re-fill the spa with water from another source with lower calcium and adjust to get the Calcium at the LOW end (like 200 ppm) of the suggested range for the winter. ,.

 

[RDspaguy]

Go too low on calcium and you will pit the marcite.

 

[mmcwhorter]

Yes, and thinking about rainwater through a mesh cover may take it below 200. Good catch. So, maybe I set it to 300 before covering.....And another idea that came to me...I wonder if it makes any sense to completely drain the spa for the winter? Hmmmmm? Anyway, I used Pumice Stone on the seats so it's tolerable. I'm going to try lightly sanding with super fine wet sanding paper to knock off all the **** and bumps from the walls. Come Fall: I'll take note of the condition before I close...and see what happens.

 

[mmcwhorter]

And yes, the pool and spa are the same when I close becuase I usually drain the spa into the pool and refill.

 

[Brett S]

might try next winter to set up a low dose acid added, maybe using a funnel and a tube running int he spa under the cover....every week or so put in a few ounces of diluted Muriatic, say 4 oz in one quart.

I’d be pretty nervous about just blindly adding acid, especially with no water circulation. If you add too much you could make the water acidic, which could also damage the spa and with no circulation the acid, which is more dense than water, will just pool and sit on the bottom of the spa and will likely damage it.

 

[mmcwhorter]

I agree, which is why I said "low dose", diluted is what I really meant instead. Something like 2-4 oz in one gallon. Pour diluted through a pre-positioned hose that goes under the cover into the spa...use a funnel. As I agree with you, my reticence to do this led me to think about simply draining the spa almost all the way down before putting the cover on. Since I have seen neighbors in FL drain pools for 3-4 months at a time, I assume there is no serious problem to drain the spa during the winter. I also assume that would stop the problem of pitted and bumpy uncomfortable walls and seats in the Spring.

 

[Brett S]

I’d still be a little nervous about just blindly adding acid, because again you may go too far and make the water acidic, which will also cause problems.

It might be hard to do with the cover on, but if you can come up with some way to get a water sample out of the spa you might be able to test the water once a month or so, then you could figure out how much acid to add to keep the pH in a good range. Maybe even leave a little utility pump in the bottom of the spa that you could turn on for a little while to circulate the water after you add some acid.

I can’t really speak to draining the spa, so I’ll let someone with more knowledge answer that question.

 

[mmcwhorter]

Actually, I was thinking about using the same hose with a primer bulb or small electrical pumping device to measure the spa water as you suggest...All Great Minds.......the hose can operate in both directions....or truth be told the way the cover is designed it is simple enough to remove two of the spring hooks with the little "baseball bat rod tool"...and flip a corner over to expose some water. I have two of those rods. I felt it was important to be able to get the cover off in any event required, as opposed to ceding that ability to others. By the way, that is the ONLY routine maintenance task I hire out for "pool service"...placing or removing the cover in the Fall and Spring. That's a two-man job and I want no part of it.