Straightforward DWC auto res top-up?

Guys i apologise, i don't mean to waste your time and i feel like i'm abusing the site, but i've been browsing through the web for two hours while stoned with no success and i'm getting increasingly nervous about leaving my DWC unattended in two days, as i seem to turn up nothing of use...
from what i gather (seen on aquarium websites) auto top-up would involve a direct feed from a separate, pHed reservoir going into my plants' buckets, with the feed regulated by a float valve...
i'm just looking for a diagram or simple tutorial to give me an idea of the parts i need.. i need to do this quick, i was stupid to leave it late but it is short notice...
i'm leaving for 7 days, plants are drinking about a litre of water a day each.. i appreciate any help guys..
peace to all

please guys.. someone out there must leave their plants unattended occasionally....

there are some rdwc tutorials that address the float valve issue
http://www.drugs-forum.co.uk/forum/showthread.php?t=59308
heres one i found

I'm surprised you dont already have one... i thought everyone running DWC had something like this...

all you need is a simple float valve, and a container of water above your other resevoir or control bucket or whatever...

here is one from my local hydro shop: http://www.atlantishydroponics.com/Merchant5/merchant.mvc?Screen=PROD&Store_Code=AH&Product_Code=FVA200&Category_Code=

basically its just like the thing that floats in the toilet... you'll have to rig it up, but you attach the water to the valve, and when the float sinks too much it will open the valve, and the water will be gravity fed into the system until the float rises, stopping the water.

an alternative would be to use float switches to turn on a water pump... this is the same thing but uses electricity instead of gravity, i'll see if i can find some of my float valve pics..

i cant find the pics of the gravity fed float valve set up - but i ended up ditching it in favor of the electronic controlled float valve... i just two float switches and put them at the water level i wanted (i used 2 for failsafe), and used a relay to turn on the top-off water pump until the switches float... here's what it looks like, this is the more confusing way to do it - but it works.

I just run a 1/4" tubing line off of my R.O. feed onto a float valve designed to accept the tubing. It really doesn't affect the PH. Admittedly, I tend to just start PPM high, and add back nutes when it gets low - maybe once a week.

i just ordered an aquarium float valve - fingers crossed that it arrives by saturday ...
anyway thanks..
for the reservoir, do you think i should pH the water, add nutrients, etc.?
I know my plants pretty well by now, and strangely I find once I top-up the water, adding nutes (3 part GHE hydro) makes the pH drop to around 5.2, and it'll fluctuate throughout the next 24 hours up to 6.2, which is pretty much spot on... so pHing the reserve water shouldn't be needed, but what about nutes? hit them with a high ppm just before i leave (they're in their 8th week of veg and at 850ppm) or just let the normal level dilute out as the week goes on...?

you could do it either way... you might as well put the nutes in the top off res... because when you come back you will still be able to enjoy not touching them for weeks at a time

hope everything works out for ya...