Ruling on using a water purification system that wastes a lot of water
Question

                I have a question regarding the usage or installation of RO. Water purifier at home.

I was searching for best purifier in the market and I came to know that RO+UV is the good technique for water purification for drinking.

I also came to know that in RO after purifying the water 50% of water goes waste..

Please let me know whether we can use that RO.
Praise be to Allah.
	Maintaining one’s health and that of one’s children and 
	family is one of the most important of priorities.

	We cannot say that exposing one’s health to danger or 
	destruction is a lesser evil and less harmful than wasting an amount of 
	water equal to the amount that is drunk. 

	Man is enjoined to preserve his health, for preservation of 
	life is one of the five fundamental objectives of Islam, which are: 
	preservation of religious commitment, life, honour (lineage), intellect and 
	wealth. So long as a person needs to purify his water, and there is no other 
	means that is as effective as this method and wastes less water, then there 
	is nothing wrong with using this water purifier, and that is not regarded as 
	extravagance, because extravagance means wasting a great deal of wealth on 
	an insignificant purpose. 

	And it was said that extravagance means spending more than is 
	appropriate on something that is not appropriate.

	At-Ta‘reefaat 
	by al-Jarjaani (p. 38)

	Water purification is not an insignificant purpose; rather it 
	is an important purpose that deserves to have wealth spent on it, because 
	polluted water is one of the main causes of disease which may destroys 
	people’s health and exhaust their wealth to an extent many times greater 
	than what will be spent on purifying water. 

	In an article by Prof. Dr. ‘Ali ‘Abd ar-Rahmaan ‘Ali, former 
	president of the Arab Union for Sustainable Development and Environment, 
	entitled Athaar Talawwuth al-Miyaah al-‘Adhbah ‘ala Sihhat al-Insaan 
	(Effects of Freshwater Pollution on Human Health), he begins his article by 
	saying: 

	The least that can be said is that it destroys human health 
	by causing internal diseases such as cholera, malaria, typhoid, bilharzia, 
	hepatitis, dysentery of all types, and cases of poisoning. End quote.

	But what is usually the case with regard to people who use 
	water purification methods is that they use them only for water that will be 
	used for drinking and cooking, and not for other domestic uses of water, 
	such as cleaning and the like. In this way one may avoid extravagance and 
	greatly reduce the level of waste.

	And Allah knows best.