Yes, liquid solar pool covers can be safe when used as directed. The active ingredients – cetyl alcohol, polydimethylsiloxane, and other minor components – are non-toxic at the low concentrations found in these products. Toxicology studies show no health risks from limited human contact or pet exposure. However, some precautions like avoiding ingestion and slip hazards are still advised.
This article examines the ingredients in liquid pool covers, how they work to retard evaporation and heat loss through forming a micro-thin film, their benefits for energy savings and algae prevention, as well as potential drawbacks like cost and water conditioning.
What chemicals are in liquid solar pool covers?
The main active ingredients in most liquid pool covers are:
- Cetyl alcohol – This is a waxy aliphatic alcohol derived from coconut oil. It makes up 5-10% of the solution. When spread thinly across the pool, cetyl alcohol forms a hydrophobic layer that prevents evaporation. It is non-toxic to humans.
- Polydimethylsiloxane – The other key component is polydimethylsiloxane, a silicone-based polymer that accounts for 0.5-1.0% of the liquid. It helps make the cetyl alcohol spread evenly and remain flexible. This is also used in shampoos and considered safe.
Other minor ingredients serve various functions:
- Fatty alcohols – Longer chain alcohols like octadecanol are added at low levels to increase film strength.
- Surfactants – Compounds like sorbitan monooleate help lower the surface tension of water so the film can spread.
- Stabilizers – Ingredients like calcium chloride prevent the polymers from coagulating into clumps.
- Preservatives – Biocides like bronopol prevent microbial growth in the bottle.
- Dyes – Colorants aid application by showing where the liquid has covered.
The concentrations of these chemicals are proprietary information held by manufacturers. But in total they account for less than 5% of the liquid volume. The rest is water to act as the carrier.
Are liquid solar pool covers safe for humans and pets?
When used as directed, liquid solar blankets are considered safe for humans, pets, and the environment. The low concentrations of cetyl alcohol, polydimethylsiloxane, and other ingredients are non-irritating to skin and eyes.
Toxicology studies submitted to the EPA have found no evidence that these chemicals pose health risks from limited contact or swimming in treated pools. The concentrations are well below levels that could cause issues if accidentally ingested.
However, it is still smart to shower after swimming and avoid drinking pool water as you would with regular pool chemicals. The cover film may feel oily to some individuals. Also keep pets from drinking large amounts.
No adverse reactions have been reported from accidental ingestion of small amounts of liquid covers. Larger quantities could act as a laxative due to the surfactant effects. But the concentrations make intentional misuse highly unlikely.
The main safety concern is slipperiness if too much product is applied. Use the minimum effective dose and avoid applying in high-traffic areas like ladders or steps. Consider roping off the pool for 30 minutes after application.
Overall, when labeling instructions are followed, liquid pool covers pose very minimal health risks for humans or pets. They can be used safely in residential pools. But as with any pool chemical, proper caution is advised.
How Do Liquid Solar Pool Covers Work?
Liquid solar blankets work by spreading an extremely thin mono-molecule layer of cetyl alcohol across the entire surface of the water. This hydrophobic layer acts as a physical barrier that reduces evaporation, heat loss, and algae growth.
Some key mechanisms:
- The cetyl alcohol film is only 0.2 – 0.3 microns thick. This prevents insulating properties but allows sunlight to penetrate to heat the pool.
- The film reflects infrared radiation back into the water instead of letting it escape into the atmosphere. This greenhouse effect traps heat.
- Evaporative cooling is minimized as the layer acts as a partial vapor barrier. Water molecules cannot readily escape into the air.
- Wind and convective heat losses are reduced as the liquid layer insulates the water from direct air contact.
- The film lasts around 5-7 days before needing reapplication. Effectiveness depends on maintaining full coverage.
Proper water chemistry is important for maximum performance. Total alkalinity of 80-120 ppm and proper pH are recommended. Shocking or clarifying may be needed if the film becomes patchy.
Benefits of Liquid Solar Pool Covers
1. Saves on heating costs
By reducing heat loss, liquid covers can lower pool heating expenses by 30-50%. This provides significant energy savings. Based on gas heater ratings of ~350,000 BTU/hour, monthly savings could be $200+ in some climates.
2. Easy application
Applying liquid covers takes just minutes compared to wrestling with solid floating blankets. Just spray or pour evenly across the surface. No anchors or storage needed.
3. Better convenience
The pool is always accessible and protected versus daily placement of solid covers. Liquids allow swimming at any time without barriers or retrieval needed.
4. Prevents algae growth
By blocking sunlight below the surface, liquid covers inhibit algae growth on pool walls and floors. This reduces the need for clarifiers and algaecides.
5. Extends the swim season
The insulation properties allow for earlier pool openings and later closings by raising water temperature. Enjoy 1-2 months longer swimming season.
Drawbacks of Liquid Solar Pool Covers
Can be expensive
While saving long-term on heating bills, the upfront cost of liquid covers ranges from $0.50 – $1.50 per sq. ft. For a 20×40 pool this equals $2000+ just in chemicals.
1. Requires continual reapplication
Unlike permanent covers, the liquid layer dissipates within 5-7 days and must be continually re-applied. This takes diligence and maintenance costs.
2. Conditions water over time
The film left behind can gradually increase total dissolved solids (TDS), pH, and calcium hardness. Monitoring and adjustments become necessary.
3. Not as insulating
Solid covers with an air gap provide somewhat better insulation during extremely cold weather. Liquids mainly retain solar heat.
4. Indoor pool concerns
Liquid covers can damage dehumidification systems. Leakage onto pool decks can also create slippery conditions. Care is needed.
Eng. Matthew Joseph Nandirio is the Founder of walkingsolar.
After graduating from the University of Houston in 2002, matt started working as a Solar Electrical Engineer for several multi-national solar energy companies.
He has a wide range of experiences including solar system requirement analysis, planning, maintaining, debugging and even solar device development through research.
He now shares his 20 years of expertise through his articles on the walkingsolar website.
Further, he is also the author of two books on Solar Technology, “Solar Power for Villages” and “DIY Solar System for Dummies”.