图片要竖起来看。it is in a

It is in a water heater cabinet in the balcony.  The water stains location on the ceiling, side wall the on the floor.  Seller said he knows nothing.  He did changed a new water heater about 5 years ago.  I am worried about slow leaking from the connections above the ceiling ( or within the ceiling).  As the seller never checked, so he did not know.  I really want to buy the condo.  But afraid there will be lots of trouble.  Seller doesn't want to do anything.  What can I do?  The best will be to open the wall to check.  Visually no water seen.  Inspector said he can not determine if this is new or old.  I have ordered a mold inspection, that is to be done today.  What else I can do.  The seller doesn't want to cut the wall.  
请各位帮帮忙出出主意，我该怎么跟卖家教室，我还需要做一些什么，我应不应该remove contingency.   The deadline is today.