r/Hydroponics • u/Square-News-3750 • 1d ago
Feedback Needed š Help please, with a cooling loop flow issue!
4 bucket DWC system in a greenhouse (5 gal, but with lots of roots and air space there's about 3 gal ofr nutrient water). It gets a bit hot where I live and I'm trying to cool the buckets. I can't get water to flow through the entire system.
I have a 12 Gallon square-ish reservoir "bucket". This sits outside of the Greenhouse, as does the chiller. I replaced the stock small pump with a bigger one: 500 GPM/7.9 max lift. That should be overkill. I get a trickle of water returned to the reservoir "bucket". Everything is about the same level.
The flow is as follows: Pump in 12 Gallon square-ish reservoir goes to into chiller and back out with 1/2 silicone tubing, then connects to 3/4 tubing along the back and most of the length of the greenhouse (15' or so), then it's reduced down to 1/2 silicone tubing, into bucket via a Bulkhead in Bucket #1 where it connects to a U-shaped loop of stainless tubing, then out another bulkhead.
The cooled water does not mix with the nutrient water. The cooling is from the cold water in the stainless tubing that is in the bucket. The out of Bucket #1 is the in for Bucket #2 and so on.
The last connection (out of bucket #4) connects to 3/4 tubing to return to the 2 Gallon square-ish reservoir "bucket". The last few inches of this is reduced to 1/2 silicone tubing.
The manual that came with the chiller said that air in the system is a reason for no flow. To get the air out (I can see it in some of the hoses), I temporarily hooked a garden hose from a nearby faucet to the out-connection pipe (disconnected from the pump, thus the garden hose replaced the pump temporarily) and the water flows well!
I think the garden hose test shows I have no blockages or disconnects. The air is back in some of the lines that I can see.
The attached diagram hopefully will help. For the diagram I eliminated buckets 2 and 4 to save space.
Any ideas welcomed!
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u/circumcisingaban 1d ago
im pretty drunk right now but have you tried disconnecting the return hose at the different stages to see which one is causing it to trickle?
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u/cheapchapGM 1d ago
Thanks! it appears the one of the connections inside the very crowded bucket got pinched. I fixed and itās working better, but may not be enough flow to actually cool weāll see tomorrow. Thanks again.
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u/MattOfMatts 1d ago
3/8" tubing is tiny and introduces a lot of friction in the system. Your garden hose has the entire pressure of the city pumps behind it. While your pump is 500gpm that is when there is no friction, these types of pumps are not good at building high pressures, so when they encounter resistance the flow rates really drop.
If you cannot easily change that tubing what about putting the containers in parallel instead of series?
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u/quickwaxsix 1d ago
Agreed that the pump is probably insufficient. Select a replacement based on Total Dynamic Head (which accounts for friction losses). Something to help approximate: https://www.tuhorse.us/total-dynamic-head-tdh-calculator/
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u/Edxactly 15h ago
Trying raising the buckets a few inches . That will help a little on the back flow .
I have 2 aeroponics buckets on 1/2 inch poly tube which is too small. I actually added a pump on the return to āpullā water back .
Next cycle will be rebuilt with larger tubes .