Please note: original poster is asking about pool building in Spain

Hi Tape;

I doubt anyone here can answer your question. Pool chemistry is universal, but pool chemicals are not, so it's often hard to answer pool chemistry questions from other countries: we don't know what's available.

Pool construction is even worse. Codes (legal requirements), equipment, available contractor skills are ALL very different from what's available in the US -- not necessarily worse -- just different.

This means that advice that might be perfectly good here, is bad advice for you, there in Spain.

Sincerely,

Ben