A simple ATO can be made with no electronic parts for about $20 using a float valve gravity fed from a container holding fresh water.  
 
If she really wants an electronic system there doesnt seem to be much in this forum about DIYing one yourself. I suggest starting a new thread in the DIY section so that maybe someone else will chime in and point you in the right direction. 
		
	
		
		
		
		
			
		
		
		
		
	
		
		
	
	
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