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Service and Maintenance

1. Protection of the Glazing

Hydrosight's underwater windows are delivered with protective boards on both sides of the glazing. The use protective boards is for:

  • Protection against impacts, as accidents might happen during construction.
  • Protection against wrong treatment of the windows, eg. faulty cleaning.
  • Protection against a combination of wind and sand, as it exists in locations near beaches.
  • Protection from the sun.

Once the water is filled, the protective plates can be removed on the wet side of the window. Impacting objects are decelerated in water, so any surface damage is minimized if the window is submerged.

Hydrosight recommends to store the protective plates for later use. (See chapter "Emptying the Tank").

ATTENTION: Do not leave transparent liner without protective board for
extended periods in the sun light. Direct UV light for several days is not
benefial for the transparent liner.

2. Cleaning the Glass

Dry Side and Wet Side While Empty

Dirt can not cling to the smooth surface of Hydrosight's windows. However, when the window glazing becomes statically charged, it attracts dust. When the windows are installed outdoors, statical charging is usually prevented by air and moisture. In closed rooms, this phenomenon is promoted by air currents, dry air and mechanical friction at the surface.

Dust can be removed with water and some dish washing liquid, using a soft, non-linting cloth or sponge. Never wipe acrylic's surface while dry. A micro-fibre cloth or other non-fuzzing paper towel, slightly dampened with water, has a streak-free cleaning effect. Anti-static plastic cleaning sets are available online, e.g. in the Plexiglas-Shop.

To remove more obstinate and especially greasy stains from the glazing, ethyl alcohol, or even better Isopropanol can be used.


  • Isopropanol should be used in small quantities, so remains can evaporate easily.
  • Remove remains of Isopropanol as quickly as possible.
  • Isopropanol should never be used where temperature exceeds 25 deg Celsius.
  • The use of Isopropanol for cleaning is exceptional and only to remove selotape etc. Do NOT use for general cleaning.

Large surfaces can be cleaned with high pressure cleaners. Use pressure of 50 to 100 bar and a water temperature of less than 50 degree Celsius.

Wet Side While Submerged

Marine water environments promote the growth of several types of algae on the glazing. Standard window washers can be used to brush algae off. The use of any type of detergents is prohibited in most seawater environments.

Chlorinated water is a care-free environment for Hydrosight's windows. Algea occur only in very little amounts and can be treated similar to treatment in marine environments. Pool cleaning robots should be tested before using.

Glass VS Acrylic: A Comparison

3. Cleaning Other

"Berndorf Flächenreiniger" is used to clean stainless steel (as used in steel pools). Nitric acid can be used to passivate metals. "Flächenreiniger" and nitric acid of 10% concentration have not shown short term effects on our window glazing.

Reference on request.

4. Polishing

Hydrosight's underwater windows can become scratched if treated wrongly.
Examples for these are:

  • Windows used in public aquariums are exposed to the public every day. They might show scuffs after a period of 10 years at some places of the glazing.
  • Windows that are cleaned with abrasive or agressive cleaning agents (see chapter "Cleaning" for proper instruction).

Polishing of acrylic is easy and well described. It can be done by any experienced party or by Hydrosight itself. Hydrosight can organize related service work such as sanding and polishing of scratches and flaws according to your need.

Polishing Acrylic & Optical Distortions

5. Emptying the Tank

Our underwater windows are made to be constantly submerged during their life time. This constant immersion might become interrupted for various reasons. For example:

  • The emptying of pools due to seasonal reasons.
  • Marine vessels visiting a dry dock.
  • Change in water level due to tidal changes.
  • A tank might be subject to changes of water level to fulfill its function.

Other temperature effects need to be taken into consideration when emptying the tank. Given as there is a large difference between water and air temperature, a Hydrosight window might undergo quick changes of temperature. The tank should be emptied slowly, possibly in the course of days.

The following rules apply for Hydrosight Windows, which are fully or partly installed outdoors:

  • Hot water tanks in a cold air environment should be emptied in summer.
  • Cold water tanks in a hot air environment should be emptied in winter.

Example: Hydrosight underwater windows have been installed in Helsinki, the capital of Finland. One side of the windows is indoors, the other side is outside. Inside the building the windows look into a heated swimming pool with a water temperature of 30 °C. The highest temperature ever recorded in Helsinki was 33.1 °C, the lowest was −34.3 °C. The recommendation is to empty the tank in summer for service, as extremely cold temperatures only occur in winter.