Spa vs. Pool: Why Hot Water in a Small Space Needs Closer Attention

Plenty of La Jolla homes have a raised spa spilling into the pool, or a spa set beside it. It's easy to treat the spa as a bonus feature of the pool and assume it will look after itself. In practice the spa is the more sensitive of the two, and it's worth knowing why. Zach's Pool Service works on residential in-ground pools and spas, and the spa is its own line of work for good reason.

Less water, same people

A pool holds a large volume of water, and that volume acts as a buffer. A swimmer, a bit of sunscreen or a handful of leaves barely changes the chemistry. A spa holds a small fraction of that volume. When two or three people sit in it, the same amount of body oils, lotions and sweat goes into far less water, and the chemistry moves much faster. A reading that's fine on Monday can be off by Wednesday after a couple of soaks.

That's the first reason spa water needs closer attention: there's simply less room for error. Adding the same chemical dose to a small spa has a much bigger effect than adding it to a pool, so adjustments are smaller and checked more carefully.

Heat changes everything

Warm water uses up sanitizer faster than cool water, and it's a friendlier home for bacteria and algae. So a hot spa asks more of its chlorine than a cooler pool does. The heat also affects scale. Warm water holds minerals less easily, so calcium is more likely to settle on the tile line, the heater element and the jets. And hot water that's kept at temperature constantly is more demanding on the heater and the pump than the pool equipment is.

If the spa is heated only when it's used, it cycles between hot and cold, and that cycling is hard on seals and fittings. Fittings that expand and contract can start to weep, which is a good reason to have someone look at the equipment regularly.

Jets, air and surface

Spas have jets and often an air blower, which mix air into the water and push it hard. That agitation drives off some of the dissolved chemicals and whips body oils and lotions into foam. If you see foam on the surface, a ring of scum at the waterline or a slimy feel on the jets, those are signs that the water has taken on more than it can handle. The spa waterline gets brushed for the same reason the pool walls are, to remove the film that clings there before it becomes a bigger problem.

The spa's skimmer, if it has one, and its strainer baskets need emptying as well. Hair and debris collect fast in a small body of water, and a blocked basket cuts the flow to the heater, which can trip safety switches or cause the heater to shut down.

Shared equipment and shared effects

In many in-ground setups the spa and pool share a pump, filter and valves. That's efficient, but it means a problem in one can show up in the other. A valve set wrong sends water to only one side. A filter that's overdue for backwashing affects both. When the weekly checklist says to "Turn on and examine equipment" and to "adjust valves," a shared spa is one of the things those steps cover.

What an owner can do between visits

• Rinse off before getting in. It keeps lotions and oils out of a small body of water.
• Keep the cover on when the spa isn't in use, which cuts debris and heat loss.
• Skim leaves off the surface and clear the skimmer basket if you see it packed.
• Notice smell, cloudiness, foam and any change in how the water feels on your skin.
• If the jets sound weaker than usual or the heater won't hold temperature, tell Zach before it turns into a no-heat call.

Water that smells strongly or irritates skin and eyes isn't a sign of too much chlorine, as many people assume. It's often a sign that the chlorine has combined with contaminants and needs to be dealt with.

Why a regular check pays off

Because spa water moves so fast, a weekly look keeps it from drifting too far in either direction. A technician who tests the spa along with the pool can see how quickly the numbers change and set the schedule to match how the household actually uses it. A family that soaks every evening has a different spa than one that uses it on weekends, and the chemistry will show it.

A spa that's checked, balanced and kept free of film is more pleasant to use and easier on the equipment. One that's ignored for a couple of weeks can turn cloudy, scale up or grow algae quickly, and the fix is a bigger job than keeping up with it would have been.

If your spa water looks off or the jets and heater aren't performing, call Zach's Pool Service at (619) 678-2240 or send a message through the contact page.