Can I leave the cover off my hot tub in the summer?

Quick Answer

It is generally not recommended to leave the cover off your hot tub during the summer months for several reasons:

Increased evaporation – Hot tub covers help reduce water evaporation, which will be significantly higher with the cover off. This can lead to the need to frequently refill the tub.
Higher energy costs – The cover acts as an insulating barrier to retain heat. Without it, your hot tub will require more energy to maintain the desired temperature.

Debris and contamination – Leaving the hot tub uncovered increases the likelihood of contaminants blowing or falling into the water.
Sun damage – The sun’s UV rays can damage the tub’s shell and components over time.

However, it may be okay to remove the cover for short periods of time when using the hot tub or performing maintenance. Some key considerations include the local climate, how frequently the tub is used, and steps taken to mitigate the risks above. Proper chemical care and filtration remain crucial as well.

Evaporation

One of the primary downsides of leaving your hot tub uncovered in warm weather is an increase in water evaporation. Hot tub covers provide an effective barrier that traps moisture and humidity over the tub.

Without a cover, the rate of evaporation can be quite high due to several factors:

Elevated water temperature – Hot tub water is typically kept between 80-104°F, much warmer than a typical swimming pool. Warmer water increases evaporation.

Large surface area – Hot tubs have a large exposed surface area relative to their volume of water. More surface area means more sites for evaporation to occur.
Wind and low humidity – Breezy conditions and dry air dramatically accelerate evaporation as moisture is carried away. This effect is most pronounced in arid climates.

Studies have shown that uncovered hot tubs can lose up to 3-5 inches of water per month to evaporation in hot, dry weather. At this rate, you may need to add a substantial amount of water weekly or even more frequently depending on your climate and usage patterns. Adding large amounts of tap water can also throw off chemical balances and deplete sanitizer levels more quickly.

Increased evaporation is inconvenient at best and expensive at worst if your local water and energy rates are high. Some homeowners associations and local laws may even prohibit excessive refilling if water shortages are a concern.

Mitigating Evaporation

If you want to keep your hot tub uncovered for any length of time, there are some steps you can take to reduce evaporation:

Add wind breaks or privacy panels on windy sides of the tub.

Set the temperature as low as comfortably possible when not in use.
Use a pool cover or solar cover to provide a partial moisture barrier while allowing access.
Only uncover the hot tub during planned usage times.

However, even with these precautions you will still need to check and top off the water level more often if not using the standard cover.

Increased Energy Usage

In addition to increased evaporation, leaving your hot tub cover off will also likely lead to higher energy bills. Hot tub covers play an important role in insulation and heat retention.

Most are constructed with dense foam insulation sandwiched between layers of vinyl or another waterproof material. Some advanced covers also feature metalized heat reflective layers and vinyl backings with sealed air pockets for additional thermal resistance.

When properly installed, a good spa cover can retain 80-90% of the tub’s heat that would otherwise be lost from the water surface. This drastically reduces the amount of time the heating system needs to operate to maintain the set temperature.

If you leave the cover off, much more heat will escape and be lost to the outdoor air:

Convection – As the water surface cools, convection currents will pull warmer interior water up and transfer heat to the atmosphere.

Conduction – Direct contact with cooler air above the surface draws heat from the water.
Radiation – Infrared thermal radiation emitted from the hot tub surface transfers heat to the sky.
Evaporation – The phase change from liquid water to water vapor is an endothermic process that pulls a significant amount of heat from the pool.

The heat loss translates directly into extended running times for the hot tub heater and pump systems. This added energy usage shows up on your monthly bill.

An uncovered tub in a warm climate may require nearly continuous heating just to maintain temperatures, whereas a covered tub may only cycle the heater a few hours per day. The cover is your most cost-effective way to control energy usage and save on operating costs.

Minimizing Heat Loss

If it’s necessary to leave your hot tub uncovered for a period of time, a few steps can help mitigate heat loss:

Turn down the thermostat – Set the water temp as low as comfortable when not in use.
Use shorter uncover periods – Replace the cover whenever the tub is not occupied.
Insulate the shell – Special coats of insulating paint can slow heat transfer.

Use a thermal blanket or solar cover – Partial covers retard heat loss when off.
Upgrade to an energy efficient model – Better insulated tubs retain heat longer.

But ultimately, the most effective way to control energy costs is to use your regular insulated cover as much as possible when the hot tub is not being used.

Increased Risk of Contamination

An uncovered hot tub is also at higher risk for contamination issues. There are several ways that debris, dirt, organic matter, and other pollutants can enter the water without a cover:

Leaves, grass, dust, etc. blown in by the wind
Insects, spiders, and other small creatures falling or crawling in

Pollen, seeds, flower petals, and airborne particles settling on the surface
Runoff and debris entering after rainfall
Splashing if strong rain or irrigation water hits the tub

Bird droppings and other animal waste

The more exposure the hot tub has to the open air, the more avenues exist for potential contamination. Left unchecked, organic matter entering the water can quickly consume sanitizer and deplete oxygen levels. Plus, objects like insects, leaves, dirt, and bird feces introduce increased populations of bacteria and other microorganisms.

Contamination puts greater demand on your chemicals, filtration system, and maintenance routine to preserve water cleanliness and clarity. And if contaminants overload your tub’s disinfection capacities, unsafe water conditions can develop.

Hot tub covers form a protective shield to keep out rain, dust, organic debris, and pests. They are a fundamental safeguard against unwanted pollution that can quickly degrade water quality.

Preventing Contamination

When leaving your spa uncovered, some contamination risks remain unavoidable. But you can take steps to minimize potential issues:

Clean the water and apply shock after each long uncover period.

Run filtration cycles for extended hours.
Frequently test and adjust sanitizer, pH, and alkalinity.
Check and clean filters more often.

Watch for debris and remove promptly from the water surface.
Rinse off any visible dirt or organics on the tub shell.
Limit uncover time to when the hot tub is occupied.

The more vigilantly you stay on top of cleaning and chemical maintenance when uncovered, the better you can counteract contamination issues. But the simplest solution remains using your hot tub cover whenever the tub is not in use.

Sun Damage

Excessive sun exposure can also damage your hot tub components and shell over time. The UV radiation and heat from direct sunlight can degrade certain materials, causing cracking, discoloration, and deterioration.

Potential sun damage impacts include:

Acrylic Surface

Most hot tubs have an exterior shell made from plastic acrylic sheet. Acrylic offers benefits like durability, easy cleaning, and good heat retention. However, acrylic can become brittle and cracked after prolonged UV exposure. Discoloration and staining may also occur.

Synthetic Cabinet

Many hot tub cabinet panels contain polymers like polyethylene or polypropylene plastic. Intense UV light can initiate surface oxidation and polymer breakdown, causing embrittlement and cracking.

Vinyl Cover

The vinyl cover material itself will degrade faster from UV rays and heat when left off the hot tub. Seams and stitching weaken first, causing tears and leaks.

Metal Components

Stainless steel, aluminum, and other metals in structural frames or jets can corrode and oxidize faster in heat, humidity, and sunlight.

Pipe and Plumbing

PVC and CPVC piping materials are susceptible to UV damage, which can lead to cracks and joint failures over time.

Electrical Systems

Circuit boards, sensors, and other electronics can malfunction sooner when exposed to moisture, heat cycles, and constant solar radiation.

Mitigating Sun Damage

Here are some tips to limit sun exposure risks if temporarily leaving your hot tub cover off:

Apply a UV-blocking wax coating to the acrylic surface.
Keep cover off only during planned usage times.

Add shade coverings like gazebos or pergolas over the hot tub.
Use UV-resistant cabinet materials like natural wood or aluminum.
Keep electrical components well ventilated and dry.

Inspect all components regularly for any damage.

But the most complete sun protection for your entire hot tub comes from simply replacing the cover whenever it is not in use. This also provides benefits like insulation, water retention, and debris protection.

Special Considerations

Some additional factors to keep in mind when weighing whether to leave your hot tub cover off in warm weather:

Local Climate

Dry and windy conditions will exacerbate evaporation, heat loss, and contamination issues from no cover. More humid, mild climates may allow for slightly longer uncover periods.

Frequency of Use

Frequent hot tub users may be willing to incur more operating costs and maintenance for convenience of an uncovered tub. Infrequent users should avoid long uncover periods.

Chemicals and Filtration

With no cover, paying close attention to water testing and chemical adjustments becomes even more critical to maintain sanitation and prevent problems.

Homeowner Association Rules

Many associations prohibit excessive refilling or unattractive coverless hot tubs. Check any applicable codes or regulations before leaving your tub uncovered long-term.

Building Codes

Some jurisdictions require hot tub covers for safety reasons and do not allow permanent removal. Be sure to follow any relevant building codes.

Insurance Terms

Leaving a hot tub uncovered for extended periods may violate terms of your home insurance policy regarding property maintenance and liability.

Energy Costs

In some regions with very high electricity rates, the expense of running an uncovered tub may become prohibitive based on your budget.

Manual vs. Automatic Covers

Manually removing and replacing a cover each use can become tiresome. Automatic cover systems eliminate this hassle for frequent users.

Consider Partially Open Covers

Solid covers that seal tightly maximize insulation and lock out debris. But some owners install vented covers or those with open mesh panels as a compromise.

Conclusion

Removing your hot tub cover for the summer is generally not advisable due to increased evaporation, energy usage, contamination risks, and potential damage from sunlight exposure. Hot tub covers provide critical functionality to maintain water cleanliness, heating efficiency, and component longevity.

However, leaving the cover off temporarily only when actively using the tub may be acceptable, if proper precautions are taken and chemical maintenance is rigorously upheld. Just be prepared for accelerated water and energy consumption, as well as more frequent monitoring and cleaning requirements.

Check applicable homeowner association rules, insurance terms, and local building codes before leaving your hot tub uncovered for extended periods of time. Also consider your specific climate, usage patterns, and maintenance commitments. In most cases though, the convenience and benefits of using a cover clearly outweigh running your hot tub without one.