How Our Filtration System Works

Chlorine: Just One Step in Our Filtration Process

One of the more frequently asked questions we receive from visitors at the pool is, “Is there chlorine in the pool?” The simple answer is yes, we are required to add chlorine by Colorado State law in order to provide a clean and safe swimming pool. But there’s more to the story than that. It takes more than just chlorine to treat our water.

Water Sources

There are three main water sources that feed the Ouray Hot Springs Pool. The Box Canon Line, the OX2 Line, and the Ball Park Line. These three water sources converge together at our Pre-Filter Vault. The Pre-Filter Vault is the point at which we begin to treat our water before it enters the pool. There are two main areas within the Pre-Filter Vault.

The Mixing Vault

First is the Mixing Vault. This is where all three lines come together. The water temperature is between 120-130 degrees and comes in at a rate of 200-300 GPM. The water coming in has a high Manganese and Iron content. This is where we pre-treat the water with liquid chlorine. We treat our geothermal water with a low dose of chlorine as a preventive measure to keep large quantities of iron out of the pool. If we did not do this, the water would turn a rusty brown due to the Iron Oxide. Ask anyone with a white swimsuit what they think about that!

The Pump Vault

Once the water leaves the mixing vault, it flows into the Pump Vault. Inside this vault is our main pump for the entire pool. This pump runs 24/7 driving water through our filtration system and out to the pool. Water from the pre-filter vault is pumped into our filtration building before going into the pool.

Filtration Building


High Rate Sand Filter

Inside the filtration building there are several large high rate sand filters. There are two rapid rate sand filter systems, the first being a Pre-Filtration System.  This system removes Iron and Manganese that has oxidized with our pre-treatment of chlorine. Second is our Re-Circulation System. This system filters the pool water on a continual basis, removing organic matter and pathogens. Both of these systems run simultaneously.







Water and Temperature Control


Manually Controlled Valves

Unknown to most of our soakers, the Ouray Hot Springs geothermal water is 100% manually controlled by our staff.  Ever wonder why you see staff members walking around with thermometers?  Every 30 minutes, water temperatures are taken in our three main pools.  If the temperatures begin fluctuating outside of our advertised temperature ranges, staff members will adjust the geothermal flow to that pool through the use of butterfly valves in our filter building.  Flow adjustment is more of an art than a science.  It takes a lot of training to discover the right balance of geothermal water that needs to enter each section at any given time.  Wind, ambient temperature and available geothermal water are just a few of the variables that must be considered when setting theses valves.  Because we have a limited supply of geothermal water available, staff sets heating priorities to the three main pools in the winter months.  The first priority is our hot section (102-106 degrees), the second priority is our shallow section (95-98 degrees) and our third priority is our activity pools (78-82 degrees).  Extreme weather events affect our ability to keep our temperatures stable.  Windy days pose challenges because evaporative loss is amplified (imagine the pool as a bowl of hot soup)

Flow Through Pool

The Ouray Hot Springs Pool is classified as a flow through pool. This means the amount of water entering the pool is the same amount of water being pushed out. The water being displaced by the fresh new water is de-chlorinated, and is released in the river. Pool staff strictly monitors this to ensure state compliance.

A More Efficient Filtration System Is Coming

So there it is! If all of this sounds complicated, well, it is. And basically, I just scratched the surface of what goes on behind the scenes. With our historic renovation project underway, the general concept of filtration at the Ouray Hot Springs will remain unchanged. However, there will be a vastly more efficient system in place providing geothermal water for you soaking pleasure. The Ouray Hot Springs Pool has staff on hand constantly monitoring the process to make sure the pool remains a safe and pleasurable experience for you and your family.


Article Written By Ron James (Lead Cashier)