Adding nutrients to reservoir

I have a drip to waste drip system reservoir. I'm doing the lucas formula (8 ml micro, 16 ml bloom per gallon) and fill reservoir with 20 gallons. The problem is, once my reservoir gets down to like 2 or 3 gallons or so, the water level is to low for my water pump to suck in water so i've been just dumping the 2 or 3 remaining gallons out and starting it fresh which a pain in the ass because i have to do it without my roommates finding out.

My question is, say i'm down to 1-3 gallons with 1000ppm (don't know exactly how much is left in reservoir), if I just add like 17 gallons at 8 ml micro/16 ml bloom per gallon will the ppm stay at 1000 or will it mess that up and mess up the nutrient balance?

Why do you have to do it without your roommates finding out?

for one two maybe 3 changes, it may be feasible, but on the longer run you really need to have a handy way to empty your res. I cannot imagine my res without a drain hole. I even make a big drain hose to empty quickly

Add water to your reservoir ever day to top it off. Run your solution for 7 to 10 days with just adding water. 7-10 days drain/clean your system mix your new nutrients. If you have a good RO/DI system you should be able to go the 7-10 days with-out having to ph/down your nutrient solution.

topfuel29 said:

Add water to your reservoir ever day to top it off. Run your solution for 7 to 10 days with just adding water. 7-10 days drain/clean your system mix your new nutrients. If you have a good RO/DI system you should be able to go the 7-10 days with-out having to ph/down your nutrient solution.

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He said he's running drain to waste so nothing is coming back into the res to throw off ph or ppm's.

On another note as long as you have an air stone or circulation pump in the res to keep it circulated I don't think you'd have any problems just topping off with nute mix instead of emptying the res every time.