News & Events

Automatic Safety Covers and Slack

One of the most frequently asked questions by our customers upon seeing the Eclipse™ Automatic Safety Cover on their pool is “why are there ‘wrinkles’ in the fabric”?.   Wrinkles are one of the indications of the slack found in a cover fabric and slack is necessary for an automatic safety cover fabric to function properly.  Below is a document provided by Coverstar Inc. that explains in greater detail the reasons for slack in any automatic swimming pool safety cover fabric.


From time to time the question arises about the need for slack in automatic pool covers and how much is enough. Regardless of manufacturer, all automatic pool cover fabrics are made wider than the width of the track. There are several reasons for this:

  1. A cover that is too tight will pull against the tracks and will not operate properly. A cover that is made too small reduces the life of the cover and mechanism, causing premature failure of both the fabric and the mechanism due to the added stress
  2. All fabric shrinks over a period of time. The amount of the shrinkage varies widely according to the type of fabric, how the fabric is manufactured, the temperature of the water, and the weather conditions. Slack is always added to the fabric to compensate for potential fabric shrinkage.
  3. In order to meet the ASTM safety standards, The cover must lie on the water, most of the supporting strength of the cover comes from the support of the water directly under it.

Each cover we manufacture is made with the slack calculated on the basis of the type of fabric, application, and unit. Any other variables that may be brought to our attention are also included. Initially, a properly sized cover will drop almost directly down from the track or deck to the water, with some folds & wrinkles as it crosses the pool. Because each cover is subject to many variables, it is impossible to calculate the exact amount of shrinkage each individual cover will have, so an approximation is made based on our past experience. Our slack formula is designed to give the cover and mechanism maximum life, as well as making the cover look as attractive as possible.

Before an order for any cover which has less than the factory specified slack is processed, we must receive a signed statement from the customer which releases Coverstar from any warranty or safety liability issues which may arise because of premature failure of the fabric or system due to fabric shrinkage.

In some cases, a portion of the slack may be taken up by lowering the water level. However, you should consult with your pool builder or service man before doing so. They can advise you exactly where the water level should be to keep the pool equipment operating properly.

The slack in the front of the cover must be spread over the length of the leading edge, keeping it away from the sides near the tracks. If this is not done, it is possible that the fabric may fold over and get caught in the track.

The leading edge loop size has been designed to give maximum flexibility in properly installing and servicing the cover.

For a downloadable copy of this document please click here