Water Care & Chemicals – FAQs

Q: What is the proper level for Bromine or Chlorine in a hot tub?  Bromine is not recommended for use in wood hot tubs, always refer to the chemical care instructions provided with new wood tub purchases.
A: Bromine is not recommended for use in wood hot tubs, always refer to the chemical care instructions provided with new wood tub purchases. Chlorine should be 3 ppm, (parts per million).

Q: What is the correct pH range for hot tubs?
A: pH level should be between 7.2 – 7.8 ppm

Q: What is the ideal range for Alkalinity?
A: Alkalinity should be between 100 – 150 ppm

Q: Can I switch from a Chlorine disinfectant to a Bromine sanitizer?
A: Yes. You can switch from chlorine to bromine without draining your hot tub or spa. You can call, fax or email Roberts Hot Tubs and we’d be happy to explain the process to you. You can also switch from Bromine to chlorine but the process is a little more intricate. For more details, please give us a call or send us an email.  Our contact information is listed below.

Q: How accurate are Test Strips?
A: Test Strips are more than adequate for your private or residential hot tubs, spas or pools.  It is important to remember that all test strips are not created equal, some are much better than others.  For accuracy, strip longevity and results you can count on, purchase quality brand name test strips by manufacturers such as Leisure Time, AquaChek or Taylor.

Q: How often should a hot tub be drained?
A: Most hot tubs require the water to be changed every 60 – 90 days.  This number of days vary based on how often you use your hot tub and how well you maintain, balance and sanitize your water.

Q: Can I use a non-chlorine pool shock product in my hot tub?
A: A non-chlorine spa shock is buffered as to not affect the ph or total alkalinity.  The non-chlorine pool shock will lower the pH and alkalinity if used.  DO NOT mix chlorine and bromine together.

Q: When I used pH Balance by Leisure Time, my hot tub water became cloudy. Why?
A: pH Balance reacts to reduce calcium hardness.  The calcium cloud will be filtered out and the filter should be cleaned.  Ideally, pH Balance should be used when calcium hardness is less than 150ppm.

Q: I start coughing whenever I take off the insulating cover off my hot tub. What might cause this?
A: Sanitation and disinfectant fumes are the most likely culprits. If the residual of the sanitizing disinfectant is high, fumes will accumulate under the cover.  Inhaling these fumes could easily induce coughing or sneezing.  Fumes can also accumulate if you don’t shock your hot tub on a regular basis. We recommend you use Renew by Leisure Time or Sea-Klear Chlorine-Free Shock.  Whenever you add any chemical to your hot tub water, it is recommended that you leave the spa cover open for a minimum of 20-30 minutes to allow any gas to escape.

Q: How often should I shock my hot tub or spa water?
A: In a perfect world, a hot tub should be shocked after each use. Once shocked, wait several hours before retesting because it takes at least that long for anything that you have added to the water to properly mix with all of the water in your hot tub. We recommend a minimum of waiting 3-4 hours after shocking before retesting.

Q:  How often should I clean my filters?
A: Pleated Hot tub filters should be thoroughly rinsed at least once a week.  Do not rinse or clean with high powered pressure washers as they can damage the filter.  To clean your filter properly, it must be submersed in a filter cleaning solution and then rinsed off thoroughly with clean water before putting it back into your hot tub or spa.

Q:  Why does foam accumulate on the surface and around the edges of my hot tub?
A:  The two main culprits responsible for foaming on the surface & around the edges of hot tubs and spas are:

  1. Bacteria – Bacteria is nothing to mess around with and you should discontinue use of your hot tub or spa immediately. The best course of action is to call in a hot tub professional or at the very least, discuss the situation in detail with your local hot tub professional.
  2. Residual Laundry Soaps & Body Oils – A good quality hot tub Defoamer should eliminate foaming caused by excess laundry soap or detergent. Many of our customers have significantly reduced or completely eliminated their foaming problems by using a quality product called Foam Out by Rendezvous.

Filter & Filter Cartridge FAQs

Q.  When should a cartridge filter be acid washed?

A.  Acid washing is perhaps the biggest single factor leading to premature filter cartridge failure! For years, service technicians and homeowners have acid washed D.E. grids. However, cartridge elements do not have the protective D.E. powder coating that grids have and can be permanently damaged by the acid.

As a rule of thumb, acid wash only when required, if at all, and never without thoroughly cleaning the element with a cartridge degreaser first.   Here’s a simple test to determine if acid washing is required; After thoroughly cleaning the cartridge with a degreasing agent, flush the cartridge with a garden hose to remove all traces of soap, etc.

Now apply several drops of acid directly to a small area of the filter media. If bubbling occurs, this indicates a build-up of calcium or minerals, and you should proceed with a mild acid soak. If no bubbling is observed, your cartridge most likely does not require acid washing.

Q.  Is there an easy way to know when to clean a cartridge filter?

A.  Cartridge filters work on the clarification process. They utilize the debris they collect as an aid to improve filtration. As a result, cleaning too often does not allow the filter to work at optimum filtration efficiency, while not cleaning often enough will shorten the life of a cartridge element.

Filter Cleaning Tip – When you replace the element with a new one, note the start-up pressure on the tank gauge. This reading is the system’s total pressure in “pounds per square inch” or psi.

Mark this point with a drop of fingernail polish or a grease pen. Then add 8 pounds to the reading and place another dot. You now have the normal operating pressure for your cartridge in psid or pounds per square inch differential. Allow the filter to operate between these two points and clean whenever the gauge reaches the higher pressure mark.

Q.  Some filter cartridges have one hard end cap and one soft end cap. Why is this?

A.  When cartridge manufacturers design a new filter element, several factors must be considered. One of the most critical is the end cap hardness. To determine the exact degree of shore hardness required, we first must look at the element sealing points.

Sealing points both position the element and prevent water by-pass. Historically, single cartridge systems all used cartridges with inside i.d. friction seals with hard end caps. This design provided both strength and pleat support. However, as filters became more sophisticated, so did end cap design.

Sta-Rite’s Posi-Flow element, for example, uses a soft vinyl bottom to both seal the inside and outside edges and lock the cartridge into the filter base, while the top end cap is a hard compound for cartridge strength and integrity.

Hayward’s Star Clear filter uses hard end caps for integrity with a soft gasket to allow a knife edge top seal. Both the new American Predator and Jacuzzi CFR designs rely on a soft top and bottom to achieve an o-ring seal.

These end cap configurations are excellent designs. Only the compounds change to meet the manufacturers’ specifications. This is just one of many reasons why Unicel builds its replacement filter cartridges to OEM design specifications and why Unicel is #1 in filter quality and reliability.

Q.  I saw a new filter cartridge made with yellow material. What kind of filter is this and why are Unicel filter cartridges white?

A.  Unicel and virtually every brand name company in the filter business uses a spunbonded, 100% polyester material called “Reemay” as their filter medium. Reemay, which has FDA compliance, is approved for milk filtration and is white to indicate purity.

Research shows no added benefit for using a yellow filter cartridge other than being a different color than everyone else. The filter cartridge you mentioned uses a less expensive version of the same spunbonded polyester material that other manufacturers use, but it’s yellow instead of white.

Some low-end manufacturers are utilizing this material to reduce costs; however, there is a significant difference in performance.

Q.  How can I tell when a cartridge filter element needs to be replaced?

A.  With no moving parts or electrical switches to fail, cartridge elements do not have a defined termination point. Instead the fine interstices of the media matrix gradually plug up over time.

In a typical hot tub or spa, the culprit that plugs the media is perspiration and body oils combined with soaps, chemicals and very fine particulate.  Assuming the filter has been properly maintained and correctly sized to the pump, determining when the cartridge is exhausted depends primarily on three factors:

1. Shorter cycle time between cleanings
2. Low water flow rate and high differential pressure
3. Catastrophic failure such as a tear in the media or center core collapse

All three are dependent upon proper spa water chemistry and following a routine maintenance schedule. Tub owners should be reminded that filter elements are plastic and should be handled and maintained accordingly.

All of the following will help maximize the life & performance of a filter cartridge:

• Clean the elements per cleaning instructions.
• Never use a stiff brush to scrub the media.
• Maintain spa water chemistry in proper balance.
• Do not allow the differential pressure to go over 8 psi between cleanings.
• Alternate two sets of cartridges when cleaning.

Q.  Sharp Pleat Folds vs. Rounded Pleats; Is There Really a Difference?

A.  Absolutely! One of the first things a filter expert will look for when examining a hot tub or spa element is the pleat fold or “knuckle radius” of the pleat. Why is this important?

If you look carefully, you will notice that some manufacturers’ pleats are very sharp while others are rounded and even appear puffy. With Reemay, or other spunbonded polyester medias, it is much easier to make a rounded fold than a sharp pleat.

Moreover, a rounded fold can mask the filter manufacturer’s inability to make straight pleats or maintain proper pleat spacing.  Unicel takes great care to make sharp pleat folds for the following reasons:

• Ease of Cleaning – Sharp folds increase the spacing between pleats making it easier to flush out loose debris.

Eliminates Bridging – Allows particles to get down into the pleat instead of laying across the top of two or more pleats. This assures maximum dirt holding.

• Full Utilization of the Pleat Surface – Allows debris to build up from the inside out, critical to obtaining the maximum cycle life between cleanings.

• Maximizes Flow, Minimizes Pressure Loss – by decreasing the surface contact between the inner pleat knuckle and center tube.

* The above pleat information pertains to spunbonded polyester filters. Paper based
filters were not considered for this article.

Q.  Why Do Some Filter Cartridges Use Support Bands, but Not Others?

A.  Support bands are almost exclusively used on pool filter cartridges to help prevent pleat flutter during the filtration cycle. The water flow through spa filters is under much less pressure and support bands would do more harm than good on hot tub and spa filter cartridges.

Q.  What is the filter cartridge cleaning procedure on a chlorine or bromine sanitized hot tub or spa?


1. Remove the cartridge from the filter housing following the manufacturer’s instructions.
2. Use a garden hose with a straight flow nozzle to wash down the filter element. Work from the top down, holding the nozzle at a 45 degree angle, and wash all the pleats with emphasis between pleats.
3. Rinse until all dirt and debris is gone.
4. For all spa cartridges and elements used in swimming pools where perspiration, suntan lotions, and other oils are present, soak the element for at least one hour (over night is more effective) in (1) a commercial filter cleaner; or (2) one cup trisodium phosphate (TSP) to five gallons water; or (3) once cup dishwasher detergent to five gallons of water.
5. Rinse the cartridge again to remove oils and cleaning solution.
6. If the filter has a coating of algae, calcium carbonate (residue from calcium hypochlorite), iron, or other minerals, soak the cartridge in a solution of one part muriatic acid to twenty parts water until all bubbling stops. WARNING: Failure to remove all oils and cleaning solution before acid soaking will result in a permanent restriction of water flow and cause premature cartridge failure.
7. Rinse the cartridge clean an reassemble housing.

*WARNING – Always wear rubber gloves and safety glasses when using acid or chlorine. Do not add water to acid. Do not mix chlorine and acid.

Please Note – Unicel does not recommend the use of diatomaceous earth (DE) with cartridge filters. DE particles can become trapped in the body of the filter and shorten cartridge life. If desired, a cellulose fiber/synthetic DE can be used in moderation.

Ozone Hot Tub FAQs

What is Ozone?

Ozone is active oxygen, O3. It occurs naturally in the earth’s atmosphere to protect us from the sun’s harmful rays.

What are some uses of ozone?

Some common uses are: pool and spa water purification, aquarium water purification, drinking water and waste water purification, meat processing and air freshening.

How long has ozone been used to purify water?

Since the late 1800’s.

How long has ozone been used to purify pool and spa water and remove odors from the air?

Over 50 years.

How does the ozone used for water purification affect the air we breathe?

The amount of ozone produced by an ozone generator is insignificant to the normal atmosphere we live in. When dissolved in water, ozone is extremely safe. Excess ozone quickly converts back to oxygen. Note: do not breathe concentrated ozone gas.

Is ozone the same as “SMOG”?

No! “Smog” is air pollution created by combustion polluters. While smog contains small amounts of ozone, it is largely composed of harmful chemicals such as carbon monoxide. In fact, smog and other pollutants may contribute to the damage of the ozone layer.

If I use ozone in my pool or spa, will I help replenish the ozone layer?

No. Because ozone reacts so quickly with contaminants in water and air, it converts back to oxygen within minutes or even seconds. Any ozone molecules that break free from the pool or spa water will convert to oxygen and never reach the atmosphere.

Will ozone hurt me?

No! In the quantities necessary to be effective, ozone is very gentle to humans and equipment in the water. However, you should never breathe concentrated ozone gas.

Does ozone have an odor?

Yes. Depending on the concentration, the odor ranges from slightly sweet to moderately antiseptic.

What bacteria and other harmful substances does ozone kill?

• Bacteria – (such as E-coli, salmonella, streptococcus, cholera) . These are micro-organisms about 1/100th the diameter of a human hair and are relatively easy to kill.
• Viruses – (such as influenza, poliovirus, hepatitis). A virus is a parasitic, infectious microbe which can cause disease in humans.
• Parasites – (such as trichina worms, pinworms, amoebae, nematodes and fungi). Parasite eggs are large in microscopic scale and relatively easy to filter out, but are generally resistant to other disinfecting methods.
• Cysts – (such as cryptosporidium and giardia). Cysts are protozoa that produce a special protective shell.
• Chemical by-products in water – such as chloramines and trihalomethenes. Chemical water can leave undesirable odors and taste.

Will ozone kill viruses?

Yes. Ozone kills virtually all known forms of viruses in water and air.

How is ozone different from chlorine?

In the quantities needed for water purification, it has no noticeable odor, taste or color. It is not irritating to humans or equipment. Ozone purifies water and air very quickly and efficiently, 3,000 times faster than chlorine. Ozone leaves no by-products except pure oxygen. In contrast, chlorine leaves a chemical by-product called hypochloric acid and additional salts in water applications.

Will Ozone reduce scum lines and foaming in spas?

Yes. With proper filtration it should completely eliminate them.

How is ozone produced?

Ozone can be produced by ultraviolet (UV) light or by corona discharge (CD).

How does ultraviolet light ozone generation work?

A special lamp gives off a specific wavelength of ultraviolet light which converts oxygen (O2) molecules into ozone (O3) molecules by splitting the oxygen molecules into individual oxygen atoms (O1) which then recombine with oxygen molecules to form ozone. This all occurs instantly inside the ozone chamber in the ozone generator.

How does corona discharge ozone generation work?

Ozone is produced by passing air through a high voltage electrical discharge or corona. Corona discharge ozonators typically produce more ozone than UV bulbs and are more efficient than the older style UV ozonators.

Can ozone damage my pool or spa equipment?

No. In fact, it is very gentle to spas, pools, and equipment. Applied properly, ozone is more gentle than any other water purifier in existence.

Can the ozone in my pool irritate skin or eyes like chlorine in pools?

No! Ozone is very gentle to skin and eyes.

How long will ozone last in my pool or spa water?

Scientific theory states that ozone has a half life of about 22 minutes in water. In residential applications, ozone reverts back to oxygen in minutes (ozone breaks down faster in warmer water).

Will water temperature affect ozone?

Wide variations in pool water temperature will affect how well ozone works. An ozone generator should be designed and sized for maximum water temperatures and bather load.

Will ozone affect my pH?

Ozone is pH neutral. It will not adversely affect the pH. Additionally, you will have lower TDS in spas with ozone, so it will be easier to adjust the pH level.

Do I still have to filter the water as often?

Yes. Because impurities are constantly being introduced into the water and the ozone is constantly destroying them, the microscopic remains will need to be filtered out of the water.