Getting rid of calcium build up

One warm July day our technicians brought 2 hot tubs in for refurbishing. We lifted the lids and groaned.

The first tub was a beautiful tuscan sun color - from the top of the acrylic all the way down to the water line. After that - just white. Chalky, unattractive white. It had a serious case of water-calcification.

The second tub was shockingly worse. Thick layers of white stone-like substance adorned the entire tub above the water line.

At first glance both tubs appeared to have the same problem, just in different places. The problems are not the same though and each would require entirely different treatment.

In this installment, I'll share with you the methods that worked on both - and more importantly - why. So next time you drain your tub and find signs of calcification staring back at you from your beautiful acrylic - you will know what to do.

Calcium build up BELOW the water line

Alberta water is naturally high in calcium carbonate due to area geology. When water sits in place for any amount of time, this type of calcium sweats out, depositing on surfaces beneath the water.

In your hot tub, the "surfaces" include heater chambers, elements, pumps, even plumbing. Over time, the interior calcium will break down and spit out of jets, adding a sandy gritty layer to the seats and floor. Calcium also builds up on the acrylic from the water line down. When you use products such as "Secure" or "Stain & Scale", they affect the calcium molecules - preventing them from sticking to surfaces. If you are not using these, expect gritty seats and waterline stains. There are 2 ways to remove calcium carbonate

1. Acidic water method: Calcium carbonate is a compound of high-alkaline earth metal. In most cases it can be easily removed by reversing your water chemistry from alkaline to acidic. It's quite a simple thing to do. DO NOT USE THE TUB DURING THIS PROCESS: - Drain and refill your tub with fresh water - Bring it up to temperature - Add a large amount of pH reducer (for well water also add several cups of muriatic acid) - Check with a test strip after 1 hour - the goal is to get bright / neon yellow for the pH, indicating it is now too acidic to be read by the test strip. Continue adjusting down until you see this.

   - keep your heat up and allow the acidic water to cycle through your hot tub for 24 to 48 hours After 48 hours, drain the water, wipe out the interior with a soft cloth. Most or all of the calcium should be gone, and your tub is ready to use again. If some staining remains, go to step 2 below:
   

2. Manual Removal: You will need a bottle of CLR, 2 clean soft cloths, a bucket of warm water and gloves - put on gloves to protect your skin (CLR is not corrosive but can irritate)

   - pour undiluted CLR onto a wet, soft cloth - begin applying it directly to calcium stains using circular movements until the calcium begins to form a greyish paste - wipe off this pasty substance with another clean, soft cloth, and rinse it in the bucket - repeat until all the visible calcium is gone - rinse the tub with a hose and sprayer, drain excess water and fill / balance as usual

   ** pouring a bottle of CLR directly into your full hot tub water will have no effect. CLR works up to a 50/50 dilution.

Calcium-like deposits ABOVE the water line If you have a white-grey chalky build up or stain above the water line - it's not caused by calcium sweating out of the water. In most cases, it's the substance "Calcium Silicate". Calcium silicate build up on hot tubs is uncommon and very difficult to remove. It's usually caused by over-chlorination and high pH gasses trapped between the water and the cover over long periods of time. Neither acid water nor CLR will remove this. To confirm you have a silicate build up - dab a small amount of muriatic acid onto the stain. If it doesn't bubble - it's calcium silicate. You can manually remove the substance if your hot tub is made of acrylic (fiberglass and other materials will be damaged by the removal). It's tricky. Calcium silicate tends to bind and integrate with other surface materials. Our problem tub was made of acrylic - so I chose to start with a hot tub product called "Secure" (SpaLife). This contains EDTA - a chemical that prevents calcium from adhering to surfaces. Applying it to the top layer of calcium silicate assists in separating molecules of the top silicate layer from the layers below.

The real magic will only happen though with the use of pumice stone and water. This stone reacts with with calcium silicate.

You'll need a bottle of hot tub Secure (stain and scale remover), a large flat pumice stone, bucket of water and 2 clean, soft cloths.

• saturate 1 cloth with Secure (or similar EDTA containing hot tub treatment)

• using pressure, rub the deposits with the cloth for several minutes

• ensure the area is well saturated

• immediately take your pumice stone and, using some pressure, begin scrubbing in circular motions

• the second cloth should be in the water bucket and used to continually wash the area (every 3 to 5 minutes) as the calcium comes loose.
  

!!! When using the pumice stone, you will see a chemical-like reaction in the calcium deposit. It is imperative to continually rinse this, and keep the area saturated

Future Prevention Once your hot tub acrylic is restored, use a hot tub scale treatment in your water weekly - such as "Secure" (by Canadian manufacturer Spalife). It will not soften your water or dissolve calcium - the calcium will still be there - but will prevent it from binding to surfaces.

If the build up was above the water line (calcium silicate) - you can take corrective action to prevent this from happening again.

1. Either reduce the amount of chlorine in your hot tub, or switch to bromine (also reduce the amount).

2. If you normally check and adjust your pH weekly - do this two times a week instead until you know your pH values are consistently neutral.

3. If you are struggling with pH values bouncing all over the place, call a professional. There are usually simple and easy ways to correct the problem and each solution depends on your water source and the hot tub chemicals you are using.