If it as simple as installing a new bulkhead then you shouldn't need a temporary tank,  livestock and water could go in a big rubbermaid or 2 while you install a new bulkhead and thead in new fittings etc.  
 
If you are comfortable having the livestock ( I don't know how much you have)  in rubbermaids with pumps running for a few days I would highly recommend getting an overflow installed. Wont have to worry about draining again. 
		
	
		
		
		
		
		
	
		
		
	
	
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