Backyard Aquaponics
A place to discuss aquaponics

To those who know something about check valves, would this work?

1. Irrigation grid on grow bed.
2. Two lines to irrigation grid, one from a gravity feed of water with a one-way check valve on it, the other from a large pump running intermittently.
3. The large pump comes on...

Would your run-of-the-mill check valves keep the large pump's water pressure out of the gravity feed line?

Extra credit question:

What if you have three beds with their own gravity lines and a line from the large pump, with check valves on each of the three gravity-fed lines. Could the large pump kick in without backing up the gravity lines?

Thanks for the info!

Yep, yep and Yep, only problem may be gravity feed lines being able to open check valves

Could be expensive but YES to all questians .Check valves here are about $20.00

Same here F&F for Plastic 25mm

Yes, but for a standard bore spear check valve they must be upright to work, water can go up, but not down. you would need a U bend to facilitate the upward pressure to open the check valve. Gravity feed would be enough to open the check valve. I just dont see why you would?

Heres 2 shots of a check valve made for the aquarium trade its a brady it will work in all positions also theres the in line brass check valve available from most farm supples it just has a flap that hangs there no springs nothing

did you get that from Adult world milne?

Thats the same check valve from waldecks except blue

Ha ha lets you go one way not the other

I have a swing check valve just under the water line on the feed to my pump to keep it from loosing it's prime. These big swing check valves don't need as much water pressure to open them but they are designed to be a particular way up so might not work for gravity feed.
Aquatic Eco Systems swing check valves

Excellent, thanks everybody!

Another thing to consider is that check valves dont operate very well when gunk builds up on them.

Thanks BF, that could be a serious PITA for this application. If the gravity lines don't have a whole lot of pressure anyway and biofilm builds then it could be a maintenance issue. I've had a venturi clog up several times due to biofilm.

Considering your warning maybe this could be done without check valves. There could be two inlets to the grid - one for the gravity feed and at the opposite end one for the pressurized feed. In order for the pressure feed to back up into the gravity lines it would have to push enough through the entire grid then up the gravity-fed pipe. It may be that significant backflow might not occur if the lines were separated by the grid. The kind of backflushing action from the pressure feed might be beneficial, to maybe clear out the continuous grid from time to time.

Duckpond, the reason I'm asking is I'm thinking about combining a continuous flow with an strong intermittent flow. The usual bed filling will be maintained through the continuous pump but every so often a big pump would suck up solids from the bottom. From using continuous pumps solids transportation can be a problem, it would be nice to have the "nuclear option" available say every two hours or so...

Putting a section of large diameter pipe on the gravity side would probably end any backup problems - the large pump would have to overcome loss from the grid and any that escaped up to the gravity side would pile up in the large pipe and increase the pressure and flow through the grid.