Ideal flow rates for NFT and DWC AP

[Chandara Khan]

Hello everyone. I am really curious about the ideal flow rate for NFT and DWC AP. Can anyone clear my curiousness out? Well, I'm using PVC pipes which have 4 meters in length and 9 centimeters in diameter. Last but not least, tell me what does Ib stand for? (measurement) .Please help answering me my questions.

Cheers !

[Chi Ma]

Lb = Pound = 16 ounces. My NFT is sort of a flood and drain. It runs for an hour and off for 3. Plants look like they are doing fine. Fish tank is sparkling. But I'm not looking for maximum plant growth. Just enough to filter the water.

[TCLynx]

more important than the flow through the DWC or the NFT is to make sure the water gets filtered enough to keep the water quality high in the fish tank (of course if one is using only DWC or NFT then separate filtration is necessary.)

 

I have about an inch of water flowing through my 15 foot long NFT pipes and it flows about what a faucet opened half way would give from the sink, I've never measured the gallons per hour.

 

I don't know the recommended flow rates for DWC

[Chandara Khan]

Hi Chi Ma! Thank you so much for your response. But, I wanna ask you for further information about your system. Well, if you run your NFT in the form of flood and drain, don't you have problems with your plant root system. I mean aren't those plants rotten when the water stop flowing? For my system, even I allow my pumps to run constantly still there is so much sludge and sediment from fish waste surrounding my net pot and the plant root.

[Chandara Khan]

Yeah, I see TCLynx getting the water filtered is really important in NFT, but  a suitable flow rate is also important since it deals with the amount of dissolved oxygen in the culture water.If it lacks DO, the plant root will be rotten. Isn't it?  Well, the flow rate of your system is about over 4 liters/minute which is contrasting to what I have been told only 0,3 liter/ minute. For the plant root in my NFT, they get surrounded with sludge or sediment from the culture water though it is pump through a clarifier, 4 biofilters and one settling tank. Some of the root systems are rotten. The dept of the water flowing through the hydroponic pipes is one centimeter (half of an inch) and each pipe is 4 meter long which is  a bit shorter than yours. Because of this , I'm think about making this dept shallower than this. What do you ?

[TCLynx]

Yea, it is important to filter the gunk out before sending the water to the NFT or in most cases DWC.  My filtration is gravel beds, if you are getting enough sludge building up in you NFT pipes to cause the roots to rot, then your filtration isn't doing the job or your flow rate is just too small to keep things well aerated.  In DWC generally additional aeration is used in the raft tanks.  NFT generally relys on the thin film being good enough for aeration but long runs can become depleted especially in hot weather or if there is sludge building up.

 

I expect my flow rate is keeping my pipes from having any major issues and the water is being pumped from a well aerated sump tank with constant plashing and additional aeration.  Even though my pipes are not "classic" nft troughs but just 4" pipe and some parts of them sag a bit so the water is deeper at some points.  They are still working for me.  I sometimes need to root prune the large basil plants to keep them from clogging the pipes.

[Matt Denten]

I have a 45 gallon vertical NFT aquaponics system set up in my office now.  I've done a few things to keep the so called "sludge" down.

 

First, my sump tank is at the very top of the unit.  This allows me to run the system with only one pump, as gravity brings the water all the way back down.  Second, the sump needs to be filled with gravel or (preferably) sand.  With sand, you can pump the water into the bottom of the sump, under the sand.  This will remove airborne sludge and trap it in the sand.

 

Also, I have 2 bamboo shrimp that seem to like the brown organics that still collect in my grow tubes.  I will often get those particles suspended by adding fresh water directly to the beginning and ends of the grow tubes.  The brown organic particles float back to the fish tank and are (mostly) eaten by the shrimp.  I have thought of putting a shrimp directly in the grow tube to eat the sludge, but I am afraid he might get caught in the roots and die.

 

As far as flow rates go, I have found them to not be critical.  Think about it in cycles.  How many times do you want the water in your system to cycle in an hour? day?  I have a 250gph pump that pumps vertically 6 feet, so in reality it might pump 100 gph or less.  My system holds a total of around 50 gallons, so it cycles about 2x an hour.  I use PVC pipes in my system and the water level is at the bottom of the last net pot in each tube.  

[TCLynx]

I'm not really trying to be picky but to avoid confusion, a sump tank is generally the lowest point in a system where the pump resides.  Also, sump tanks normally have fluctuating water levels.  Saying your sump is at the top and filled with sand, well personally, I would call that a bio filter or a sand filter.

Anyway, sounds like you have a pretty good little system going there.  Turning over the fish tank volume twice an hour is a good thing.  Generally the bare minimum is one time an hour and then one usually needs additional aeration.

 

Matt Denten said:

I have a 45 gallon vertical NFT aquaponics system set up in my office now.  I've done a few things to keep the so called "sludge" down.

 

First, my sump tank is at the very top of the unit.  This allows me to run the system with only one pump, as gravity brings the water all the way back down.  Second, the sump needs to be filled with gravel or (preferably) sand.  With sand, you can pump the water into the bottom of the sump, under the sand.  This will remove airborne sludge and trap it in the sand.

 

Also, I have 2 bamboo shrimp that seem to like the brown organics that still collect in my grow tubes.  I will often get those particles suspended by adding fresh water directly to the beginning and ends of the grow tubes.  The brown organic particles float back to the fish tank and are (mostly) eaten by the shrimp.  I have thought of putting a shrimp directly in the grow tube to eat the sludge, but I am afraid he might get caught in the roots and die.

 

As far as flow rates go, I have found them to not be critical.  Think about it in cycles.  How many times do you want the water in your system to cycle in an hour? day?  I have a 250gph pump that pumps vertically 6 feet, so in reality it might pump 100 gph or less.  My system holds a total of around 50 gallons, so it cycles about 2x an hour.  I use PVC pipes in my system and the water level is at the bottom of the last net pot in each tube.  

[Chandara Khan]

Yeah, now everyone I got the ideas saying that flow rate should be between 0.5 to 1 liter / h and the depth the of the water should be 1 millimeter, but I find it hard to keep my system with these suggested rate and depth.

[TCLynx]

Perhaps that is the best in Hydroponics but Aquaponics and bio-slime will make sticking to that more difficult.  I flow way more water through my NFT pipes that that.

[Chandara Khan]

Yeah, to my idea , I think depth is not a major concern comparing to the the sludge or suspended solid that enter the pipe. Thus the crucial thing to do is to eliminate the amount of this kind of thing from covering the plant root system. Anyway the flow rate is import. By the way TCLyxn, could tell me the how high the slope of your pipes?

[TCLynx]

My pipes have minimal almost no slope.  There is between and inch and half an inch of water in the bottom for the most part.  The flow is probably close to a liter a minute though I've never measured it.

 

The really important part is the water going to my NFT pipes (if you can really call them NFT with that much water in them.) has been filtered through media beds so there isn't a problem with sludge or suspended solids.  You really must filter out the solids before you send the water to NFT pipes.

[Matt Denten]

Just wanted to add my NFT pipes are about 3-4 feet long and are only raised about 1/2"-1".  The beginning of the pipe has just a few centimeters of water, whereas the end has <1 in. of water.  Pipe diameter is about 3 in.