Winterizing Your Northern California Swimming Pool: To Drain or Not to Drain?

by James Florence


Swimming pool winterization is an important task, even if you live in a mild climate region. But should you drain your pool for the winter in Northern California? Photo: Royal Pools of Santa Clara, Inc. ©2018

If you’re a pool owner living in or near the Greater San Francisco Bay Area, it’s time to start thinking about winterization. You’ve likely heard of people who drain their pools for the winter, or perhaps you’re one of them. But should you drain your pool for the winter in Northern California? Is it really necessary? If not, what does pool winterization entail? For that matter, is it ever necessary to drain a pool? To get answers to these and other questions, we spoke with Mike Doucette, general manager of Roger’s Pool & Spa Service Inc. in Sebastopol.

Why drain a pool?

Before we discuss pool winterization specifically, let’s look at a few potential reasons a swimming pool might need to be drained.

A swimming pool’s plaster coating doesn’t last forever and will eventually need to be replaced. Typically, residential pools need to be resurfaced every 20 to 30 years, which requires the water to be completely drained.

Structural issues and other significant problems may require a swimming pool to be drained prior to repairs.

Major cleaning
Sometimes pools need to be drained to restore a minimum level of cleanliness and sanitation. “We get calls every spring from customers who say, ‘I let my pool go all winter and now there’s a quarter-inch of algae on the walls and two feet of dead leaves at the bottom,’” says Mr. Doucette. “In some cases, it’s nearly impossible to get the water back to usable condition without draining the pool, scooping out the debris and pressure washing the algae off the walls.”

Diluting total dissolved solids (partial draining)
“Every chemical you put in a pool contains inert ingredients,” explains Mr. Doucette. “If the pool doesn’t get diluted, those inert ingredients will gradually add up until you get what’s known as total dissolved solids. At this point, you need to drain a foot or two of water from the pool and refill it with fresh water to dilute the chemicals.”

Should you drain your pool for the winter in Northern California?

Some Northern Californians routinely drain their pools each winter so they don’t have to maintain them. But is this practice worthwhile? The reality is that it makes more sense in other areas of the country. On the East Coast, for example, pool equipment components can get damaged when the water inside of them freezes. In dry areas like Southern California and Arizona, the lack of rainfall increases the chances for pools to develop total dissolved solids. However, in Northern California, the ample rainfall and mild winter temperatures make draining a pool essentially pointless.

In some cases, draining a pool during winter in Northern California isn’t just unnecessary—it can actually cause major problems. “Depending on its location, a pool that’s drained prior to winter can be susceptible to damage due to changes in the water table,” says Mr. Doucette. “Swimming pools are self-contained bodies, and the water in the pool is part of that dynamic. If an empty pool gets a lot of water beneath it, it can act like a boat and actually float up out of the soil. We’ve seen it here in Sebastopol. We had one customer who drained their pool for the winter and it ended up floating three feet out of the ground! If you’re in a low-elevation area, especially one that’s prone to flooding, draining your pool during winter is risky.”


Draining a pool during winter in Northern California isn’t just unnecessary—depending on your location, it can actually lead to major problems. Photo: Paradigm Concrete & Construction, Inc. ©2018

Tips for Winterizing Your Northern California Pool

Rather than draining your pool for the winter, Mr. Doucette recommends leaving the water in and maintaining it throughout the season. Fortunately, this isn’t hard to do…provided you know what you’re doing. “The main thing is keeping the chemicals balanced,” he says. “You don’t have to run the pool pump very much during winter—you can probably get away with an hour a day or less, depending on what type of pump you have. The chemical balance is the most important part. If that’s not right, you can filter 10 hours a day and it’s not going to help.”

Another winterization measure to consider is adding freeze protection to your pool system. Even in areas of Northern California that don’t get snow (like the San Francisco Bay Area), it’s not unusual for temperatures to reach the point of freezing. The main concern here is the pool equipment components, which can sustain damage if water freezes inside of them. Utilizing a sensor, a freeze protection unit prompts the pool’s pump to turn on when the outside temperature reaches a low threshold. Circulating the water ensures it won’t freeze and damage the pool equipment.

Furthermore, Mr. Doucette says rainy days can help with winter pool maintenance. “Rainwater is our friend because it naturally dilutes pool water and prevents total dissolved solids. If you know a storm is coming, I recommend uncovering your pool. If you want to keep your pool covered because of safety concerns, another option is using a pump to collect rainwater that accumulates on the pool cover. Just make sure the cover is relatively clean so the water isn’t filthy.” 

Basic guidelines for draining a pool

Even if you don’t plan on draining your pool for the winter, you may need to drain it at some point for resurfacing, cleaning or repairs. In this case, follow these guidelines:

Plan for a dry time of year. To prevent potential issues, don’t plan a major pool project during the winter. While it may interfere with swimming season, it’s safer to plan for summer or early fall, when the water table is at its lowest.

Inquire about legal regulations. Prior to draining your pool, consult your city water department to find out if there are any legal requirements or restrictions in place. In some cities, completely draining a pool is prohibited, in which case you’ll need to file for an exemption.

Most legal regulations on pool draining are concerned with preventing pollution. Since pool water is full of chemicals, draining it into the wrong outlet can result in contamination of natural water sources. That’s why it’s illegal to drain pool water into storm drains or nearby creeks. Typically, pool water must be drained either into a sewer outlet or onto a safe area on your private property.

“If you live within the city limits, you would normally drain your pool via a clean-out that goes directly to the sewer,” says Mr. Doucette. “If, on the other hand, you live on a large property, you have the option of draining pool water onto an open area of your landscape. However, it needs to be a level area that’s away from natural water reservoirs. That way, the water will get filtered through the earth before it hits the water tables.”

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