"i've Never Seen This Before"

[movingchicane]

Hello everyone,

I've got the mother of all problems with my pool and the experts are all telling me, "I've never seen this before".

Details: Inground pool, salt system, white plaster sides, only 3 years old, calcium at 900-1000 ppm. We use a roof mounted solar system to warm the water 5-8 hours per day and hardly ever use the heater.

I drained it just last year because of the same problem. The water here is hard to begin with and can be anywhere from 600-800 ppm out of the hose.

Two different pool service companies have tried to lower the calcium levels with chemicals balancing etc. They can't get it done.

The cell was cleaned just 2 months ago and now it's completely caked with calcium and needs to be cleaned again. The water is beautiful and crystal clear. But the surface is rough to the touch and hard on the feet. We've been using descalers to combat that, but now small brown marks are showing up on the plaster. They almost look like bird droppings and are hard to remove.

The interesting thing is that I believe this to be water temperature dependent as well because we have an attached spa with a spillover into the pool. The spa is naturally always warmer than the pool and the brown spots showed up there first and not in the pool. Now the spots are starting to show up on the most shallow areas of the pool, so it appears the warmer the area of the pool/spa, the more the brown calcium deposits.

My pool guy says some guy by the name of Dr. Laury (sp?) recommended tsp. I've done a search and understand this might raise algae levels, but that is not ever a concern with my pool as I mentioned earlier, it's super clear water.

I'm at wits end and don't know what to do other than try this tsp but need to know how much in a 23,000 gallon pool/spa?

TIA

[movingchicane]

Just a quick note, the pool and spa is not used very much. My pool guy swears, we wait until after he leaves and then throw a pool party with 15 people 6 days a week, but that's just not the case. My kids and I use the pool maybe 1 day a week during the summer to fall and never in the Oct. to May period.

[chem geek]

There are some metal sequestrants on the market that work more with calcium, but that's only a partial solution and would need to be added frequently since they break down over time.

You could try and manage the high CH in several ways:

1) Use a pool cover to cut down on evaporation. When the water evaporates and then gets refilled with fill water, whatever is in the fill water gets added to the pool. So with fill water high in CH, the CH in your pool will rise from evaporation/refill.

2) Try and dilute your pool water using rains. If you get enough rain to overflow or to partial drain, then that will help since rain does not have CH.

3) Lower your Total Alkalinity (TA) significantly. If you are using chlorinating liquid or bleach, you can probably go down to 60-70 ppm TA. With a lower TA, you should also be able to keep the pH from getting above 7.5 as well.

4) Raise the Cyanuric Acid (CYA) level to 80 ppm if your pool is exposed to direct sunlight (using a pool cover as in #1 above would be better, however). This will reduce the loss of chlorine to sunlight letting you turn down your SWG on-time and that will lower the rate of pH rise. You have to maintain an FC of 4 ppm if the CYA is 80 ppm.

5) Add 50 ppm Borates to the pool. This will act as a pH buffer slowing the rise in pH and will also keep the pH from rising as much in the SWG cell at the hydrogen gas plate which is where scale forms, so the Borates should reduce the amount of scale. They may also help you lower your SWG on-time.

See Water Balance for SWGs for more info and also look at the rest of the Pool School including getting yourself a good test kit, either the Taylor K-2006 or the TF100 from tftestkits.net.

Richard

[quantumchromodynamics]

You are right about this being temperature dependant. As the temperature increases, carbon dioxide is forced out, which reduces the water's ability to hold calcium. Warmer water cannot hold as much calcium as colder water. This is counter intuitive because most people are familiar with warmer water being able to dissolve more solute.

I think that the best solution is to contact a water softener company to see about removing the calcium. You can divert part of the filtered water through a softener system to remove the calcium. You can install a softener system for the fill water as well.

The fact that you are using a salt system may interfere with a water softener being used to remove calcium from your pool water. You may have to do a partial drain, and refill with softened water.

[movingchicane]

Thanks for the feedback. I'm going to print this page and give it to my pool service guy and try different things.

Rain water is not an option as I live in semi-arid southern california. In fact, we're on a 15% water reduction mandate because of a prolonged drought condition in the state.

I've thought about the water softener, but that would only be on an auto fill basis and not to refill the entire/ or 3/4 of the pool. There is no way for a softener to produce that much soft water to refill a pool.

I'm wondering if I should move away from the salt based system and go to the old fashion chlorine tablets?

[quantumchromodynamics]

A water softener company can do this. Tell them that you need to fill your pool. Tell them how many gallons and what the calcium level is in the fill water. They will come out and set up the number of tanks needed to do this. After the pool is full, they will return and remove the tanks. The tanks will be rented for the time required to fill the pool. They will not be permanently installed.