Can You Fill a Hot Tub With Well Water?

Untreated well water contains a number of impurities that can cause harm to spas. So is it possible to fill a hot tub from a groundwater well?

It’s safe to fill a hot tub with well water. However, the high mineral content of groundwater needs to be treated using specialist chemicals. Doing so avoids staining and scaling to the spa and its components. A large quantity of the impurities can be removed by attaching a pre-filter to your hose before filling.

In this article, I show you:

  • How untreated well water affects your spa
  • How to treat well water to prevent damage

The effects of using well water in hot tubs

While homes that rely on well water usually have softeners and filters fitted, those are usually connected to the indoor plumbing only. Here is how well water affects hot tubs.

Water quality

The great thing about well water is that it is mostly free of contamination. Groundwater is naturally filtered deep underground over a period of decades, meaning that no additives are necessary.

However, there are certain issues that arise when filling a hot tub from a groundwater well. Although groundwater is naturally pure, it often contains high levels of minerals and metals, which are the result of it sitting below ground level for such a long time.

High levels of minerals such as calcium and magnesium are usually present in well water, meaning that the water is hard. Some of the issues that hard water causes include scaling, cloudy water, skin and eye irritation, and increased running costs.

Left untreated, hard water may even expose you to harmful bacteria. This is due to high levels of calcium preventing sanitizers from dissolving and dispersing properly, which renders them ineffective.

Among the many minerals and trace metals found in groundwater, the presence of iron is one of the most troublesome for hot tubs. Iron can discolor the water, tinting it a greenish-brown. Water discoloration leads to staining of the spa shell, as well as to bathers’ swimsuits.

The presence of metals and minerals also impacts the pH and alkalinity levels of the water. These issues mean that it requires more work to balance the water, especially if you’re unfortunate enough to have the dreaded combination of low pH and high alkalinity. But don’t despair.

The good news is that it’s perfectly possible to get safe, crystal-clear water that your hot tub will love simply by following the steps listed a little later on.


Another concern for those wanting to fill a hot tub from a groundwater well is the risk of burning out the pump.

Good quality pumps should have no trouble working for several hours. After all, many homeowners that use a well allow the pump to run for many hours at a time to water the backyard.

Filling a hot tub requires a lot of water, perhaps in excess of 500 gallons (2000 liters). The last thing you want is for the well to run dry, causing irreparable damage to the pump. So you need to ensure that the well you have access to has a sufficient supply of water.

A well’s flow rate is dependant on how quickly it is able to refill. Around 600 gallons (2300 liters) per hour is considered a high flow rate, and anything less than 150 gallons (600 liters) per hour is low. Make sure to err on the side of caution to avoid burning out the pump.

How do you treat well water in a hot tub?

There are 3 stages for preventing scaling and staining in your hot tub when using well water. First, attach a pre-filter to the hose before filling. Secondly, use a stain and scale product to treat calcium levels. Thirdly, add metal sequestrant to ensure that iron and other harmful metals remain locked in solution.

Treat water with pre-filter

You need to treat well water in the same way you would if you were dealing with hard water but with the addition of spa metal removerOpens in a new tab. to get rid of harmful metals, such as iron and copper, that are present in water from groundwater wells.

The first thing to do is to purchase an inline pre-filter. Never fill your hot tub from a groundwater well without attaching a pre-filter to the end of the hose.

Pre-filters remove up to 98 percent of the impurities lurking in the water, making it easier to balance the water chemistry after you’ve filled up.

Treat calcium hardness

Total water hardness is a measurement of calcium and magnesium levels. But when it comes to hot tubs, only the calcium levels are important.

It’s a good idea to invest in a calcium liquid drop-count kitOpens in a new tab. so you can get a precise reading of the calcium hardness levels. Drop-count kits are much more precise than test strips, enabling you to make the necessary minor adjustments.

Unfortunately, lowering the calcium level is a lot more difficult than raising it. If your home’s water is treated with a water softening system, you can combine the treated water with water coming directly from the well.

If mixing waters is not an option, then the best solution is to use Vanishing ActOpens in a new tab.. Instead of adding chemicals to the water, Vanishing Act is placed over your spa’s intake to remove the calcium particles naturally.

Adding a stain and scale controlOpens in a new tab. product helps to keep the calcium level where it needs to be. The chemical prevents scale by bonding to the calcium ions in your spa water.

After tackling the calcium hardness levels, you now need to deal with the trace metals inside the groundwater. Most importantly, you want to get rid of any iron.

Treat iron and other metals

There are two ways to get iron out of hot tub water. The first method is to use a metal sequestrant to keep the iron locked in solution. The second method is to use a water clarifier to coagulate the iron particles together so that they are large enough to be removed by the filter.

My preferred way to deal with iron and other metals is to use a metal sequestrant called Metal GonOpens in a new tab.. Instead of removing the iron, it prevents it from falling out of solution, ensuring it doesn’t cause staining or damage to the spa shell and plumbing.

You’ll need to make using metal sequestrant part of your spa maintenance routine as it will dissipate over time. Even if your water is clear, you still need to monitor the levels of iron and other metals on a monthly basis using metal test stripsOpens in a new tab..

If you want to go the water clarifier route, I recommend Metal MagicOpens in a new tab.. Clarifiers remove iron, copper, silver, and manganese from the water by way of coagulation, which prevents staining and protects plumbing and other components.

While it’s great to get rid of metals from the water, clarifiers take some time to work. It also means having to remove and clean the filter on a more regular basis as the coagulation leads to the filter clogging more quickly.

Joshua Milton

Joshua Milton is a seasoned hot tub enthusiast. With many years of experience in the industry, he offers valuable insights on hot tub maintenance, health benefits, and relaxation techniques.

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