Efficient Pool Heating

Summary

Have Technical Pool Repair:

1. program your control system for maximum efficiency
2. upgrade your eyeball fittings to venturi return fittings, and
3. use a liquid solar blanket.

Here are the details and explanations:

Inefficient Design Features

Negative Edges

Some pools are more efficient to heat than others. Pools that have negative edges (also called infinity pools or vanishing edges) are not efficient to heat. The reason is that as the pool water flows over the negative edge it cools. Thus, if you are trying to heat a pool like this, turn off the negative edge pump when heating the pool.

Waterfalls

Waterfalls also cause heat loss. Turn them off when heating.

Pool and Spa Combos

The most common type of pool in the Inland Empire of Southern California is the pool & spa combo. Both are part of the same system and when filtering the pool, water is returned to both the pool and spa and you have a spillover from the spa to the pool. While not as wasteful as the negative edge or a large waterfall, this spillover does cause some heat loss. To maximize the retention of heat, set the valves so that you minimize the time that the spillover operates. For instance, if you have automation, you can set up the system so that when heating the pool, the valves turn to isolate the pool. To keep the spa clean, you can program a separate filtration cycle just for the spa. Finally, to prevent the spa from slowly draining, you will also need to program a very short spillover time to ensure that the spa stays full.

Return fittings in the walls

The ideal way to heat a pool is from the bottom up. A few pools have deep heat returns where the heated water is returned to the bottom of the pool. Most, however, have returns in the sides. Since warm water rises to the top (and since the water in most pools is returned via wall fittings near the top), this results in a foot or so of warm water at the top and colder water at the bottom. Since much of the water is being drawn into the filtration system from the surface via the skimmer and returned near the surface, the heater will only be measuring the temperature of the water in this top warm layer. It will therefore stop heating when this top layer has warmed up to your set point. The bottom, however, will still be cold. To counter this effect, have Technical Pool Repair replace your standard eyeball returns with venturi fittings. These direct the water downward and have slots in the top that draw the warmer surface water down into the pool. This combination mixes the water better and allows your pool heater to more accurately measure (and therefore more completely heat) the entire pool, not just the surface.

Covers

The biggest obstacle to heating a pool is heat loss. Whether you heat your pool with a gas pool heater, solar panels, or just rely on direct sunlight, 80% of whatever heat that goes in will be lost due to evaporation.

As water evaporates there is a phase change from liquid to vapor. This phase change is an endothermic reaction—meaning that heat is absorbed from the water as the water evaporates. If we can cut down on evaporation, we can stop the primary source of heat loss.

A cover is the best way to minimize evaporation and lessen heat loss.

Automatic Covers

Auto covers (vinyl covers that run on tracks and open and close via a motorized reel and pulley system) are the easiest to use. However, these covers work best on rectangular pools and very few pools in our area have them nor are they designed to accommodate one. If you were to design an efficient pool, it would have an auto cover.

Solar Covers

These are the bubble covers that float on the surface of the water. They are generally pulled off by hand onto the deck, but they can be used with a reel that makes removal a little easier. It helps to have two people when opening or closing these as they can be awkward. It is often discouraging to clean a pool with a solar cover as when you first look under the cover, the pool will be relatively clean, however, when you pull the cover off, the debris that has blown onto the cover will rinse off into the pool making it look worse than when your first looked. Second, since these covers are typically only used in the spring and fall, they often harbor algae when not in use. When first putting them on for the season, you often introduce an algae bloom into your pool.

Solar Rings

An easier to handle alternative to the solar blanket is a set of solar rings. These rings are about five feet in diameter. You add as many as needed to cover as much of your pool as practical. Since individually these are smaller than a solar cover, they are easier to remove for use or cleaning. It is, however, not recommended that these be stacked and left in the sun when off the pool, so they are still somewhat challenging to deal with.

Liquid Solar Cover

While the least effective, a liquid solar cover is by far the easiest to use and least expensive option. A liquid solar cover is a product that you add weekly. It is lighter than water so that it forms a thin film on the surface of the pool thereby cutting down on evaporation. If you use one, it is recommended that you leave the pump off on cool nights so as to not disturb the surface tension and maximize the sealing effect.