If your swimming pool has high calcium hardness, cyanuric acid (CYA), phosphates, or total dissolved solids (TDS), you may have been told that it’s time to drain the pool and start over with fresh water.
For years, draining and refilling has been one of the traditional ways to address water chemistry that has become difficult to manage. But today, pool owners have another option: reverse osmosis pool water purification.
So, which option makes more sense?
The answer depends on your pool, your water source, local conditions, and why the water needs treatment in the first place. Before draining thousands of gallons of water, it’s worth understanding the differences between a traditional drain and refill and mobile reverse osmosis.
Why Do Swimming Pools Need to Be Drained?
As pool water ages, minerals and other dissolved substances can accumulate. Calcium hardness, CYA, TDS, and other water chemistry issues can eventually reach levels that normal pool maintenance cannot adequately correct.
Draining the pool removes the existing water so it can be replaced with new water.
The problem is that new water doesn’t necessarily mean better water.
This is especially important for pool owners in Boerne, San Antonio, and the surrounding Texas Hill Country, where hard source water is common.
The San Antonio Water System reports that its typical water hardness ranges from 15 – 20 grains per gallon. That means homeowners who drain a pool may be replacing hard pool water with another source of hard water.
What Happens When You Drain and Refill a Pool?
A traditional drain and refill removes most or all of the existing pool water before replacing it with municipal, well, or delivered water.
Depending on the property, replacing that water isn’t always as simple as turning on a garden hose.
Some homeowners rely on well water, while others may need to have thousands of gallons of replacement water delivered by truck.
Depending on the pool size, location, water source, and delivery requirements, trucking in replacement water can cost roughly the same as or potentially more than having the existing pool water purified through Reverse Osmosis (RO).
And there is another important difference:
Trucked, well, or municipal water is not the same as RO-purified pool water.
You may be replacing the water, but you’re also introducing the minerals and hardness contained in the new source water.
Why Draining a Pool Isn’t Always the Simple Option
Cost isn’t the only consideration. Draining certain swimming pools can create additional concerns.
Fiberglass pools, for example, require special consideration before draining. Groundwater and hydrostatic pressure can also create problems when the weight of the water inside the pool is removed.
Expansive soil conditions found in parts of South Texas can add another variable.
The time of year matters as well. With the intense heat experienced throughout the San Antonio area, particularly from approximately April through October, leaving certain pool surfaces empty and exposed may create additional concerns.
These are some of the reasons many local pool professionals are cautious about draining pools.
That doesn’t mean a pool should never be drained. It means draining should be an informed decision based on the pool, property, water source, and reason the water needs to be replaced.
How Is Reverse Osmosis Different?
With pool water purification, Waterman’s brings mobile reverse osmosis equipment directly to the pool.
Instead of discarding the existing water, the water is circulated through a specialized filtration process that removes unwanted dissolved material before returning purified water to the pool.
The process can significantly reduce:
- Calcium hardness
- Cyanuric acid (CYA)
- Total dissolved solids (TDS)
- Phosphates
- Other dissolved contaminants
Waterman’s process typically allows approximately 80% of the existing pool water to be retained, substantially reducing the amount of replacement water required.
In other words, instead of throwing away the water and replacing it with another source of hard water, reverse osmosis purifies the water you already have.
Drain & Refill vs. Reverse Osmosis
| Consideration | Drain & Refill | Reverse Osmosis |
|---|---|---|
| Existing pool water | Removed | Purified |
| Water conservation | Most or all water replaced | Approximately 80% retained |
| Calcium hardness | Reduced based on replacement water | Significantly reduced through filtration |
| CYA | Reduced | Significantly reduced |
| TDS | Reduced based on replacement water | Significantly reduced |
| Phosphates | Depends on replacement water | Can be significantly reduced |
| Replacement water | Large amount required | Significantly less required |
| Pool remains full | No | Yes |
| Water chemistry | Must be rebalanced | Must be rebalanced |
| Ground/soil considerations | Can be a concern | Pool remains filled |
| Structural repairs/renovation | May require draining | Not a replacement for draining when structural work is necessary |
Neither solution is right for every situation.
The question is which solution makes the most sense for your particular pool?
“But Isn’t Reverse Osmosis More Expensive?”
This is one of the most common questions we hear, and it’s an important one.
If you’re comparing only the initial price of draining a pool with the cost of reverse osmosis, draining may sometimes appear less expensive.
But the initial price isn’t always the entire story.
Consider the cost and availability of replacement water. If water needs to be delivered, trucking thousands of gallons can significantly change the economics of a drain and refill.
Then consider the quality of that replacement water.
If you drain a pool because the calcium hardness is too high and refill it with hard source water, you’re immediately introducing calcium and minerals back into the pool.
Reverse osmosis takes a different approach.
Instead of paying to dispose of existing water and replace it, you’re investing in improving the quality of the water already in your pool.
Both options will require the pool chemistry to be properly rebalanced afterward, but the starting water quality can be dramatically different.
A Real 22,000-Gallon Pool Example
One Waterman’s customer had a 22,000-gallon swimming pool with high calcium hardness, elevated CYA, and phosphates.
The homeowner planned to drain the pool and have replacement water delivered by truck.
Before doing so, a local pool store told him about Waterman’s Pool Water Purification.
He discovered that reverse osmosis could address the water chemistry problems without completely draining his pool or bringing in approximately 22,000 gallons of replacement water.
He chose Waterman’s.
After the purification process, the pool water was properly balanced with significantly lower calcium hardness, CYA, and phosphate levels than what you would’ve gotten from draining or a water truck. In fact, it was mostly RO-quality drinking water!
Instead of throwing away the water, he was able to restore it.
When Does Draining a Pool Make Sense?
Reverse osmosis isn’t intended to eliminate pool draining altogether. There are situations where draining is necessary.
If a swimming pool requires structural repairs, resurfacing, renovation, or other work that requires access to the pool shell, draining may be the appropriate option.
That’s why Waterman’s doesn’t believe every pool owner should automatically choose reverse osmosis.
We believe pool owners should understand both options before making the decision.
Before You Drain Your Pool, Know Your Options
If you’ve been told that high calcium, CYA, TDS, or other water chemistry issues mean you need to drain and refill your swimming pool, there may be another option.
Waterman’s Pool Water Purification helps pool owners throughout Boerne, San Antonio, and the surrounding Texas Hill Country restore their existing pool water using mobile reverse osmosis.
Before draining thousands of gallons of water, let us evaluate your pool and determine whether reverse osmosis is a better solution.
Your pool may not need new water. It may simply need better water.
Ready to Find Out Which Option Is Right for Your Pool?
Frequently Asked Questions
Is draining and refilling a pool cheaper than reverse osmosis?
It depends on the pool, water source, and location. While a basic drain and refill may initially cost less, homeowners who need water delivered by truck may find the total cost comparable to or greater than reverse osmosis. Replacement water quality should also be considered.
Can I safely drain a fiberglass swimming pool?
Draining a fiberglass pool requires careful consideration because groundwater and hydrostatic pressure can create risks when the weight of the pool water is removed. Pool owners should consult a qualified pool professional before draining.
Does filling my pool with municipal water reduce calcium hardness?
The result depends on the hardness of the source water. San Antonio-area municipal water is naturally hard, so refilling a pool introduces calcium and other dissolved minerals contained in that water.
Does reverse osmosis eliminate the need to rebalance pool water?
No. Both a drain and refill and reverse osmosis treatment require the pool water chemistry to be properly balanced afterward.
When should I drain my pool instead of using reverse osmosis?
Draining may be necessary when a pool requires structural repairs, resurfacing, renovation, or other work that requires the pool to be empty. Reverse osmosis is designed primarily to address water quality and chemistry problems while allowing the pool to remain filled.