Pools Unlimited

Friendly people...expert advice.

716 - 677 - 4100
3903 Seneca St. W. Seneca, NY 14224

Technical & Troubleshooting Information

Included here is some troubleshooting and technical information for pools and hot tubs, along with links to manufacturers' web sites.

Technical Information for Pools and Hot Tubs

Miscellaneous Mathematical Formulas

Here are some commonly used mathematical formulas that are helpful in the pool and hot tub industry for calculating pool volumes and chemical dosages among other things.

Circle Area = Pi (3.14) x Radius²

Circumference = Pi (3.14) x Diameter or 2 (Pi) 3.14 x Radius

Diameter = C / Pi (3.14)

Radius = C / 2 Pi (3.14)

Rectangle or Square Area = length x width

Triangle Area = 1/2 base x height

Cube or Rectangular Box Volume = length x width x height

Standard/Metric Conversions

inch x 25.4 = millimeter            millimeter x .0394 = inch
foot x .3048 = meter            meter x 3.2808 = foot
yard x .9144 = meter             meter x 1.0936 = yard
mile x 1.6093 = kilometer          kilometer x .6214 = mile
quart x .9463 = liter               liter x 1.0567 =  quart
ounce x 28.3495 = gram         gram x .0353 = ounce
pound x .4536 = kilogram               kilogram x 2.2046 = pound
degrees F x 5/9 = degrees C        degrees C x 9/5 +32 = degrees F

Units of Capacity

1 Gallon = 4 Quarts = 8 Pints = 16 Cups = 128 Oz
1 Quart = 2 Pints = 4 Cups = 32 Oz
1 Pint = 2 Cups = 16 Oz
1 Cup = 8 Oz. 

Glossary of Pool and Hot Tub Terms

Here are some commonly used terms in the pool and hot tub / spa industry.

ACID DEMAND: - The amount of acid required by your pool water to achieve the proper pH level.

ACID: - A chemical that lowers pH and total alkalinity when dissolved in water by providing hydrogen ions. Hydrochloric acid and sodium bisulfate are two commonly usd acids.

ALGAE: - A microscopic one-celled plant organism. These organisms are continually introduced into the pool water by rain showers, wind, dust storms, etc...

ALGAECIDE: - A chemical used to kill algae

ALGAE SPORES: - Dormant algae residing in the atmosphere, which get introduced to the pool by rain, wind, dust storms, etc...

ALKALINE: - A condition when the pH of water exceeds 7.0 on the pH scale

BACTERIA: - An unseen, but dangerous organism that occurs in all water. Bacteria is controlled by disinfectants such as chlorine or bromine.

BASE DEMAND: - The amount of soda ash required to increase the pH level of pool water to the ideal range of 7.2 - 7.6.

BOTTOM DRAIN: - A water intake located at the bottom of the pool. The water is drawn into the filter from this before it is cleaned and returned to the pool.

BROMINE: - A sanitizer and disinfectant that kills bacteria and prevents algae.

CARTRIDGE FILTER: - A filter which utilizes a replaceable element and does not require backwashing.

CHLORINE:- A strong oxidizing agent for use as a sanitizer and disinfectant to kill bacteria and prevent algae.

CHLORINE, AVAILABLE:- Residual chlorine available to destroy bacteria on contact.

CHLORINE DEMAND: - The amount of chlorine required to destroy bacteria or algae.

CONDITIONER: - Also called Chlorine Stabilizer, Stabilizer, or Cyanuric Acid. A sun-screening chemical that reduces the loss of chlorine due to evaporation by the sun.

CORROSION: - A chemical reaction caused by unbalanced water which causes metals or minerals to dissolve.

CYANURIC ACID: - Also called Chlorine Stabilizer, Stabilizer, or conditioner. A sun-screening chemical that reduces the loss of chlorine due to evaporation by the sun.

D.E.: - Diatomaceous Earth: - A white powder added to an “earth” filter to clean the pool water of small organisms, dirt, etc...

ELECTRONIC IGNITION: - The ignition system on a pool heater that causes a heater to light through a spark ignition. There is no continuously burning pilot light in these heaters. This system is like your new gas stove where you hear the clicking sound when you are lighting it. Compare to Millivolt ignition.

FAST DISSOLVE TABLETS: -  A stabilized chlorine tablet that dissolves fast, typically within a half hours time when placed in the pools skimmer basket with the filter running.

FILTER: -  The part of the filter that cleans the water.

FREE CHLORINE RESIDUAL: - The active chlorine level in pool water after the chlorine demand is satisfied.

G.P.M. - GALLONS PER MINUTE: - Used to compare flow rates of various filter systems.

G.P.H. GALLONS PER HOUR: - Gallons per Hour - flow rate of pumps. (Compare to G.P.M.)

HARDNESS: -  The amount of calcium, magnesium, iron, carbonates, sulfates, chlorides, nitrates, phosphates, and silicates dissolved in the water. Scale deposits are formed when high levels of hardness are present in the water.

IN LINE CHEMICAL FEEDER: - An In-Line Chemical feeder has the main filter hose going through the chemical feeder. (Compare to Off-Line Feeder).

MAIN DRAIN: -  See Bottom Drain.

MILLIVOLT IGNITION SYSTEM: -  The ignition system on a pool heater which has a pilot light that runs continuously. Compare to Electronic Ignition.

MURIATIC ACID: -  Hydrochloric acid in liquid form used for lowering total alkalinity and pH of water.

OFF-LINE CHEMICAL FEEDER: - An off line chemical feeder is connected to a filter with smaller hoses that attach to the existing hoses of the filter system. (Compare to In-Line Feeder)

OTO: - An chemical used to determine the amount of chlorine in pool water.

P.P.M. - PARTS PER MILLION: - A measurement used to calculate how much chlorine, hardness, or alkalinity is present in pool water.

pH. : - The total of all acidic or alkaline particles in the water. The recommended range is 7.2 - 7.6.


PHENOL RED: - A chemical used to determine the pH level of water.

PRESSURE SIDE CLEANER: - A pressure side cleaner is a cleaner which is propelled around the pool by water pressure forced through the cleaner. The forced water is either from your filter system, or by a separate  "booster" pump  These cleaners pull a bag around behind them to catch dirt, leaves, and other debris from the pool. (Compare to Suction Side Cleaner)

PUMP: - The part of the filter that, along with the motor, determines the flow of water to the filter.

RETURN: - The part of the pool where the water is returned to the pool after it is filtered.

SAND FILTER: - Traditionally a filter that uses silica sand as the media for filtering out dirty and other impurities.New media is available to use in the sand filter to improve filtration. This includes zeo-sand and glass beads.

SCALE: - A crusty white, gray, or brownish substance that attaches itself to tile, plaster, or metal in pools. Normally caused by excessive water hardness.

SCRIM: - The weave of the material in winter covers. This is the number of weaves per inch in the cover. A 12 x 12 scrim is a stronger cover than an 8 x 8 scrim cover. Covers are generally sold as either 5 x 5, 8 x 8 or 12 x 12 scrim.

SHOCK TREATMENT: - Super Chlorination accomplished by adding 5 - 10 times the normal chlorine dose to help free up the free chlorine.

SKIMMER: - An inlet at the water level to catch large debris floating on the water.


SODA ASH: - A chemical, Sodium Carbonate, that raises pH.

SODIUM BICARBONATE: - A chemical that raises the total alkalinity of water.

STABILIZER: - Also called Chlorine Stabilizer, Conditioner, or Cyanuric Acid. A sun-screening chemical that reduces the loss of chlorine due to evaporation by the sun.

SUCTION SIDE CLEANER: - A suction side cleaner is a cleaner which attaches to the skimmer or a dedicate vacuum line (on an inground pool) and draws the water directly into the filter. These cleaners work like your manual vacuum, except they move around the pool automatically. The dirt, leaves, etc... which are picked up are then filtered out of the water by your filter system

TEST REAGENTS: - Various chemicals used for testing pool water - chlorine levels, pH levels, etc...

TOTAL ALKALINITY: - The number of carbonates, bicarbonates, and hydroxides, measured on p.p.m., that are present in pool water.

TURNOVER: - The period of time required to circulate a volume of water equal to the water volume of the pool.

VELOCITY: - The rate of movement of water measured in gallons per minute.

Troubleshooting pool and hot tub problems. 

Here are answers to some commonly asked problems related to swimming pools and swimming pool equipment.

I have sand going into my pool when I run my filter.

The most common problem is a broken “lateral” in the bottom of the filter. In order to find the problem, you need to remove all of the sand from the filter and inspect the components inside the filter. If any of the “laterals” are cracked, or if the center “standpipe” is cracked, it will allow sand to blow back into the pool. The “lateral” usually unscrew from the base of the “standpipe” for easy replacement. Make sure you order the proper length lateral for your filter.

I have earth going into my pool when I run the filter.

The most common problem is a torn or damaged “finger”, grid” or “element”. The earth is put into the filter through the skimmer. It is then trapped in the filter when it pushed against the “finger”, “grid” , or “element”. If the element is cracked or torn, instead of trapping the earth in the filter, it goes back into the pool. To find the problem, you need to visually inspect the internal components of the filter and look for holes in the nylon grid material. If you have a Hayward Perflex filter, make sure all of the bolts and nuts are in place, and that the plates that hold the “fingers” are not cracked. A missing bolt or cracked plate will allow the earth to pass through the filter and return to the pool.

I have a sand filter and have dirt going back into my pool when I filter. 

The small dirt particles are passing through the sand in the  filter. You can solve the problem by changing the sand (if it has been in the filter over a year for aboveground filters, or over 5 years for an inground filter); or utilize a clarifier or sand aid product to help trap the small dirt particles.

My vacuum head keeps sticking to the bottom of the pool.

The brushes on the bottom of the vacuum head are worn. When you vacuum, the suction is causing the brushes to collapse and the vacuum head then sucks to the liner. You should replace either the vacuum head or the brushes.

My filter is very noisy. 

The noise is coming from the motor. The bearings in the motor are worn out. You can either have the bearings replaced by a motor shop, or you can replace the whole “motor/pump” of the filter.

When I turn my filter on, my circuit breaker goes off.

The bearings in the motor, or the windings in the motor are bad. The motor needs to be replaced. You can try to run the motor on a different electrical outlet to rule out a problem with your electrical wiring. If the problem continues, replace the motor.

My heater will not turn on.

Try to backwash the filter and then restart the heater. The heater has a “pressure switch” (a safety device) which will not allow the heater to operate if there is not adequate water flow through it. If the problem persists, call a qualified technician for service. One or more of the components may be defective - thermostat, hi limit switches, on/off switch, etc..

My kids hair turns green when swimming in our pool.

The presence of copper in water will cause light colored hair to turn green. To remove the copper, add a mineral remover to the water. Extremely high levels of copper can cause sever staining of the pool liner. The source of copper can be from the use of algaecide which uses copper, a winterizing kit which uses copper, or from a deteriorating heater core - caused by low water pH

My pump will not prime.

There are many possible causes. Check each of the following.

              1). No water in the strainer pot.
              2). Strainer pot lid not on tight.
              3). Damaged strainer pot lid o-ring.
              4). Water level in the pool is below the skimmer.
              5). Strainer basket or skimmer basket is clogged.
              6). Closed valve in the plumbing system.
              7). Pump is on low speed (two speed pump units only).
              8). Air leak(s) in the suction line.

I have low water flow, and the pressure on my filter is high.

There are two possible causes, (1). the filter needs backwashing, or (2). there is a restriction in the return line.

I have low water flow and low pressure on my filter.

           Check the following:

              1). Strainer basket or skimmer basket is clogged.
              2). The impeller is clogged.
              3). Air leak in the suction line
              4). Restriction in the suction line.

My motor will not turn on.

             Check the following:

               1). Power switch is off.
               2). Circuit breaker has tripped
               3). Timer circuit is in off mode.
               4). Motor shaft is locked because of bad bearings
               5). Impeller is locked by debris.

Links to manufacturer's web sites. 

Below we have listed links to various pool product manufacturers web sites. Many of these products are available at Pools Unlimited - many we stock, others we can special order with a couple of days turn around time.


Hayward Pool Products

Jacuzzi Pool Products

Jandy Pool Products


Speck Pumps

Sta-Rite Pool Products


If you have any questions about any of the manufacturer's above or their products, give us a call at 716-677-4100. Thank you.




(716) 677-4100


3903 Seneca St.

West Seneca, NY 14224