No. Repair costs are only deductible in the tax year they are incurred. You can amend a tax return to claim that cost up to 3 years back. Since this was done 5 years ago, amending is a waste of time as any additional refund that may result due to amending will not be refunded or credited.
Besides, repairs costs have absolutely no effect what-so-ever on the cost-basis bottom line, whereas property improvements do.
Your leak would probably not qualify as a property improvement, but as a repair expense.
Repair
Those expenses incurred to return the property or it's assets to the same usable condition they were in, prior to the event that caused the property or asset to be unusable.
Property Improvement.
Property improvements are expenses you incur that retain or add value to the property. Expenses for this are entered in the Assets/Depreciation section and depreciated over time. Property improvements can be done at any time after your initial purchase of the property. It does not matter if it was your residence or a rental at the time of the improvement. It still adds value to the property.
To be classified as a property improvement, two criteria must be met:
1) The improvement must become "a material part of" the property. For example, remodeling the bathroom, new cabinets or appliances in the kitchen. New carpet. Replacing that old Central Air unit.
2) The improvement must retain or add "real" value to the property. In other words, when the property is appraised by a qualified, certified, licensed property appraiser, he will appraise it at a higher value, than he would have without the improvements.
Property improvements must be depreciated over time starting from the date placed in service. Waiting until the year of disposition to claim a property improvement can result in the cost basis increase being offset or exceeded by the depreciation you "should" have taken increasing your tax liability in more ways than one.
