Why Do I Have a Rough Hot Tub Surface?


Have you ever tried to relax in your spa only to encounter a rough, sand paper feel along the surface of your hot tub? That kind of scratchy build-up along spa walls can damage bathing suits or become difficult to remove over time. This is a very common issue for spa owners so there is a wealth of information on how to diagnose and fix the problem of your rough hot tub surface.

Why Does This Happen?

If you get rough build-up along your hot tub walls that feels like a low-grade sand paper, there are usually a few different culprits. You’ll want to diagnose and start to remedy it because it can build up very quickly and the problem can escalate.

First: Your pH. In your spa, the pH levels should be maintained at 7.4-7.6. Warm water mixed with high pH can affect calcium and cause it to settle on the surface of your spa.

Second: Calcium hardness. Calcium or total hardness in your water can also contribute to scaling on your spa. Often the calcium comes from mineral rich fill water that isn’t sapped from the water sufficiently.

Third: Alkalinity. Alkalinity (often referred to as total alkalinity) is a measure of buffers in your water that help control pH levels. High alkalinity often results in high pH which in turn causes scale to form. Total alkalinity levels should be maintained between 125-150 ppm.

How Do I Fix It?

The first thing you’ll want to go a hold of us a good water test kit that will help you know where your pH, hardness, and alkalinity levels are so you can begin getting back to normal.

Step 1: Adjust your chemicals to get the correct levels of pH and alkalinity. Using your test kit, check the water every 4-6 hours while adjusting to make sure your pH gets between 7.4-7.6. Water that has the correct chemical levels should help the scale loosen and begin to dissipate on its own if it’s not a severe or long-lasting problem.

Step 2: Scrub the hot tub surface to try and loosen the scale. If it’s pretty fresh, it should rub off easily with a soft rag and you won’t need to drain the tub to get rid of it. If it’s a little more significant, try a soft nylon brush. If the residue leads your water cloudy, that will probably add to your work load afterward.

Step 3: If you have a more firmly deposited scale, there’s a good chance you’ll need to drain the spa completely and scrub the surface. You might consider using a product made specifically for spa cleaning like ProTeam Surface Clean along with a pool and spa scrubber brush to remove the scale build up. Pay special attention to the area around the jets as well as the hot tub walls.

Avoid using household cleaners because they will affect your water’s chemistry upon refilling. If it does not say that’s it’s specifically for hot tub use, it could also scratch or damage the acrylic. Make sure you also sufficiently rinse out the spa before attempting to refill because small amounts of anything disruptive can lead to foaming.

Step 4: If it has become apparent that draining and refilling the spa is necessary, consider using a spa pre-filter, particularly if you’ve had calcium hardness issues. A pre-filter helps remove excess minerals from the water prior to filling the tub. Filtering out these minerals will ensure you don’t have to do as much adjusting to the water afterward.

Step 5: Once the tub is refilled, now is the time to balance your chemicals to ensure they adhere to the recommended levels. Adjust the pH levels to the lower side of normal at first, then check them often and adjust when needed.

Step 6: Add a stain and scale preventer like Spa Pure Stain and Scale Preventer. Continue to add to your water according to manufacturer instructions to help prevent additional build up.

The key to maintaining a healthy spa environment that is bothered by hot tub scale or other irritating water issues is to maintain proper water chemistry. To achieve that, test often, use a good kit, and make adjustments ASAP.

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