Swimming pool or water tank?

I have been looking online at properties that state they have a swimming pool. The photos look more like water storage tanks. Are these suitable for swimming as they don't appear to have any filter/pump system. Thanks in advance for any help.

A definition of a pool: A pond of water, of variable dimensions, with an intended use for bathing, swimming and practicing any swimming related sports.

Many classifications can be made according to its size and works execution. According to its use they can be classified into public pools, common pools and private pools.

Regarding their regulations, pools are subject to a specific regualtion, composed of National, Regional (or of the Autonomous Communities) and local rules.

National Regulation on this matter is contained in an Order of 31 May 1960, which regulates the regime of public pools and an order of 12 July 1961 which sets the rules for private pools.

Competences on this matter have been transferred to Autonomous Communities.

What region is located the pool you are refering to?

• Thank you Maria, my question was in relation to were these pools suitable for swimming as they did not have filters or pumps. Do they just turn into frog ponds with time?. 
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They must have their own system for water purification and renovation

Thank you Maria

I faced the same problem when I was trying to find a pool for my friends. Really strange pool, and I had no idea how to install them