Broken Water Pumps?

Does anyone know what happens when a water pump breaks? Can water flow backwards? I'm designing a recirculating DWC system and since I don't have much space I'm going to put the main resivour below my 5 gallon buckets. I'm going to put a float valve on the drain line going back to my main res so it can't overflow that way, but if my water pump breaks and water starts flowing backwards it could overflow the main res.

AEA,
I can tell you my experience. Most hydro pumps are designed so that they WILL backflow. In E&F, that's how the tray drains...back through the pump. So I would imagine a broken bump would behave the same.

What you'll need to do is to insert a check valve...which is a one way valve that will prevent backflow. Hope that helps.
JD

Thanks, you even answered the question I didn't ask: where to find 1/2 inch one-way valves. I only saw the aquarium air hose sized valves when I looked, the bigger ones are all called "check valves".

You want to avoid all this check valve nonsense. Restriction.

If designed properly, levels of all buckets and controller-reservoir will be at the same level. Active pumped feed from controller to bucket sites with passive return (larger diameter than feed).

1/2" returns plug with roots easily and if you feed a bucket site faster than your return line can level your system you'll overflow.

Use larger returns. Level system. You won't need check valves.

My design can't overflow, I have a float valve in the lower res on the return pipe in case it's faster than the pump, and an overflow pipe in the 1st bucket in case any of the pipes between the buckets or the return line get clogged. The overflow pipe should also make enough noise that I notice. I'm also going to use paint strainers as filters over each pipe to keep the roots in the buckets. They're washable and only $10 for 5.

http://www.amazon.com/gp/product/B00C2A9L0Q/ref=ox_sc_act_title_6?ie=UTF8&psc=1&smid=ARULJ0CQDU067

I can't make a level system, so I have 2 choices: make a system like I designed or stick with the basic DWC. The check valve I chose needs 1 psi to open, which is about as much pressure as 30 inches of water, so I also found a stronger pump for about $5 more.

A swing check?

I saw one that claimed to need only 0.33 psi and one that said 1psi, both with springs, but now I cant find either. I might just get one with a spring (1/2lb of force; that's 2.5psi with a 1/2" pipe) and break it off. One of the review said the spring is easy to break with some pliers, and they all look pretty similar.

Use a swing check valve.

No spring to fight. Just install in horizontally level.

For some reason the cheapest swing valve on Amazon is $12 when the cheapest swing/spring combo is $5. This one looks like it should work vertically without the spring so I wouldn't have to add any bends to the pipe.

http://www.amazon.com/Valterra-200-C05F-Swing-Spring-Combination/dp/B00B95U5NW/ref=sr_1_3?s=industrial&ie=UTF8&qid=1394782079&sr=1-3&keywords=1/2+inch+swing+check+valve