Ruling on eating from the university canteen if the plates are not washed seven times after having been licked by dogs
Question

                In our university we have a canteen..very often its seen that the plates left over after having food are licked by dogs..the canteen staff wash the plates..but not 7 times they wash as they routinely do..what is the ruling to have food there in those plates when u know that the [;ate may have been licked by dog and the washing not followed as prescribed in sharriah?.
Praise be to Allah.
    Firstly: 

    Muslims narrated in his Saheeh (279) that Abu Hurayrah 
    (may Allah be pleased with him) said: The Messenger of Allah (sa) said: “The 
    purification of the vessel of one of you, if a dog licks it, is to wash it 
    seven times, the first time with dust.” 

    An-Nawawi (may Allah have mercy on him) said: This clearly 
    supports the view of ash-Shaafa‘i (may Allah be pleased with him) and others 
    who say that dogs are najis (impure), because purification is only needed in 
    the case of impurity.

    End quote from Sharh Muslim

    For more information please see the answers to questions no.
    2453 and
    46314 

    Once it is established that the saliva of dogs is impure 
    (najis) and that the vessels that the dogs have licked cannot be purified 
    except by washing them in the manner described in the hadeeth, then what you 
    have to do is advise the canteen workers and emphasise to them that they 
    have to make sure that the plates are not left where the dogs can reach 
    them. If it so happens that they forget some of them or neglect to protect 
    them from being licked by the dogs, then they must be washed seven times, 
    the first time with dust. 

    If they respond to your advice and requests, then there is 
    nothing wrong with you eating in their canteen; if they do not respond then 
    do not eat anything from these plates of theirs. 

    And Allah knows best.