The plumber forgot to close the water line; is he liable for damage that was caused because of that?
Question

                What is the shariah say about compansation.when someone unintantionly causes any financial damage to any person,should he be liable to pay compansation or not?

problem detail is as under.

I have a flat on the first floor of an apartment and on the ground floor there is a chemist store.my flat is empty no one is staying there. one day i came to know that my water pump was not operating, so i took a plumber with me to take the water pump out of the main water line and give the pump to motor winder to repair it,plumber took the motor pump out of the main line but forgot to close the main line with a cork.after completing the task we closed the door and went away.
the next day when the water force was high the water came up and started filling on the floor of my flat,but unfortunately some water went in the chemist shop on the ground floor of my flat and causes some damage to his laptop. now the owner of the shop want compansation from me can i have to pay the compansation or not?all that happen is absolutely unintentionly and also it was a mistake of plumber not from me. and also cost of repairing of the laptop said by the owner of the shop is 12000 rupees while his son says 13500 rupees. both are saying diffrent cost so it is also doubt full . plz clarify what shariat says .
Praise be to Allah.
      The general principle with regard to material damage is 
      that the one who damages something is liable for it, whether he did it 
      deliberately or by mistake, but there is no sin on one who did it by 
      mistake. 

    A hired worker -- such as the plumber -- is not liable unless 
    he overstepped the mark or was negligent. What you mentioned about him 
    forgetting to close the main water line is regarded as negligence and 
    carelessness, so he is liable for whatever was damaged as a result of that. 

    Al-‘Izz ibn ‘Abd al-Salaam (may Allah have mercy on him) 
    said: Liability dictates compensation, and compensation is not waived in 
    cases of forgetfulness. End quote. 

    Qawaa‘id al-Ahkaam, 2/4 

    Al-Zarkashi (may Allah have mercy on him) said: Forgetfulness 
    means that there is no sin in cases of damage, but it does not mean that the 
    person is not liable. End quote. 

    Al-Manthoor fi’l-Qawa‘id, 
    3/275. 

    In al-Mawsoo‘ah al-Fiqhiyyah (7/167) it says: If a 
    hired worker is neglectful, then he is liable. End quote. 

    Based on that, the plumber is the one who is liable for the 
    damage caused to the laptop. The basic principle with regard to liability is 
    that what can be replaced must be replaced, and if the damaged item cannot 
    be replaced, its value must be paid instead. So he has to buy something to 
    replace the damaged part, if possible, otherwise he has to pay its value. 
    The amount in question should be determined in consultation with experts. 

    And Allah knows best.