Backyard Aquaponics
A place to discuss aquaponics

I'm trying to figure out what size drains I want to use so I can order uniseals / bulkhead fittings... I know the main thing is to make sure my drain is capable of handling at least as much water as my pump will pump, but I wanted to see if this all makes sense or not to someone who has actually done it before I get started...

The pump I am currently using is a Jebao DC9000 which is capable of pumping 9000 L/hr (2377 gal/hr) and capable of up to about 4.2 meters (14.1ft) head. I'm not sure what the actual head will be that I'll be pumping, but I would not expect more than about 1.2 meters (4ft). Looking at the flow chart for the pump that drops me down to about 7000 L/hr (1849 gal/hr) at 1 meter head. Originally I was thinking I would use a 2" (50mm) drain in each of the grow beds and in each of the fish tanks, as well as the filters, but I believe a 2" drain would be capable of up to 12491 L/Hr (3300 gal/hr). If my pump is only going to pump 7000 L/hr at 1 meter head then I think I could get away with 1.5inch drains which should allow 2100 gal/hr (7950 L/hr)...

Do you think that would be adequate or should I go with the 2inch drains just for a little safety factor? Not all of the water will flow through each of the grow beds, so really I think as long as the filters are capable of handling the flow then the grow beds could actually go with smaller drains really...

Looking at it from a total volume stance, my fish tanks will be roughly 300 gallons + 200 gallons plus 60 gallon filters (two 30 gals), and the maximum grow bed water capacity would be 259 gal (assuming they were all DWC, which they won't be so it will be less due to the grow bed media taking up most of the grow bed space) that puts me at about 819 gallons in the entire system. That only puts me at about 2.5x turnover per hour (and that's assuming constant flood... so if I tried to do flood/drain I'd have even less), do I need more than that? My fish tank experience tells me I should be looking for more like 10x turnover per hour for proper filtration but I'm not sure if that holds true for aquaponics?

The rule of thumb for aquaponics is turning over the FT at least once an hour - a lot of people go for twice, but you definitely don't need ten times! With aquariums you're dealing with a much smaller total water volume, so a reasonable water flow through the filter becomes many more tank turnovers.

For the SLOs etc in the FTs, definitely go for the bigger piping you're thinking of or even size it up some more; friction and corners etc will slow the flow down and you need the wiggle room. I went with 5cm (2") piping in my SLO and through my RFF, aiming for 3,500 L per hour flow and thinking I'd given myself plenty of extra capacity, and ended up with it being juuuuust enough to handle about 3,000 L/h after I diverted part of my pump capacity back to the sump. You can get impressive flows through small pipes under pump pressure, but you are not gonna get 3,000+ gallons per hour through two inches under gravity, not even close. The drains from the growbeds can be considerably smaller, but if they need to run a long way (some of yours definitely do) they'll work much better if the smaller pipe from the growbed dumps into a larger pipe to run back to the sump.

Also, quick question, are you thinking of possibly doing timed flood & drain? The bit in your last paragraph about getting lower tank turnover if you do flood & drain makes it sound like you are. Timed flood & drain gives you muuuuuch more flexibility in sizing your growbed drains than siphoned flood & drain because it's basically impossible to make them too big. (It's possible to make the little holes in the bottom of the standpipes too big, but not the standpipes and drains themselves.)

I haven't really decided on what I was going to do for flood/drain or constant flood etc. Currently I'm running constant flood because it's just the easiest for my test system, but long term I might go with a timer flood/drain just for the energy savings since I would like to make the greenhouse run completely on solar panels eventually that way it's not increasing my electric bill in the long run.

As for the flow rates I was going by this chart (water flow chart #1) https://flexpvc.com/Reference/WaterFlow ... Size.shtml I don't know the validity of it, but I'm sure there is probably a calculation out there for it (just a little above my math level or interest in validating the chart!)

I think what I'll do is run a 2" SLO in each of the fish tanks and I will also run a 2" drain from the filters, but then I'll drop down to 1.5" drains out of the grow beds. I don't think I will need to run multiple drains together if I put my sump in the middle, but I'll build the growbeds before I do any plumbing and then figure out at that point if I think it would be neater/cleaner to run a larger 3 or 4" drain across the greenhouse or if I'll be OK just running individual drains back to the sump. I think running the individual drains might result in fewer fittings to reduce the flow rate of the drains.

Howdy,
I agree with Mel. Go with 3" (76 mm) on the SLOs. Stick with 1.5" on the drains, I think you'll be happier if you do.

Also, if you're still planning to consolidate the flow from the FTs after the RFFs, those pipes will have to be bigger again!

I'm going to consolidate the flow, but I don't anticipate needing more than 2" drain for the entire system, so the 2" SLO's in the two tanks will be pretty oversized already since the pump will split the water in two tanks. It's also pretty easy to reduce the flow if I get to a point where the 2" isn't capable for some reason because the Jebao DC9000 has an adjustable flow rate with five different speed settings. So if all I need is 1-2x+ turnover rate per hour I will not need to run the pump at full speed.

....I really don't think that's gonna be enough. I know the diagrams and tables you've linked to say it will, but they also say those figures only apply to straight (and probably short) pipes; your plan has multiple sharp turns going through two filters and then long, loooong pipes. The flow rate is gonna drop like a stone.

I've got 2" pipes, sharp turns going through one filter, and a very short distance between FT and sump. If I put the full output of my pump through my FT (3,500 lph according to my pump's flow chart and my head height), it backs up above my SLO outlet; if I tried to put 7,000 lph through there I'm pretty sure it would overflow! So, er, I strongly suggest you put together a trial setup with 2" pipes coming out of your IBCs and then joining together and going through a bunch of 90 degree turns before dumping into your sump, and see what happens when you turn the pump on to your planned level, before building the whole thing.

(If I'm wrong and it works perfectly I will totally admit that I am wrong and bear it in mind for the future, I promise! )

...and I have just reread your last post, and it looks like you're actually planning much lower flow than the 7,000 lph you mentioned in an earlier post? and also I have just noted that it is Really Late and I should have gone to bed about two hours ago, so I may not be mathing well. Please disregard earlier post if you are actually bringing your total system flow down below 3,000 lph or so, and forgive tired twitchy me for inappropriate panic.

I don't have any way to measure the flow that I'm actually getting out of the pump, so I'm just trying to get a rough idea to make sure I'll be OK. I think my pump will be plenty powerful, so it probably won't need to run at full speed... I should be able to run it at whatever speed I need to not cause a flood. Right now it is running on the lowest speed since it is only about 200 gallons of water and one grow bed. I currently have two 1" drains in the grow bed and it is pretty much keeping up with just one of them, the other drain just gets a very slight trickle through it.

I received the uniseals yesterday that I had ordered last week. I ended up getting four 2" uni-seals and two 1" uni-seals, so my plan is that I will build the filters and get the plumbing from the fish tanks to the filters worked out, then I will run the plumbing from the filters to a temporary sump tank that I can move my pump to and have the water pump from the sump to the grow bed (and maybe split it in to the other fish tank even though I don't have anything in it right now.. idk I might wait on that and just run the fish tank through one filter for now for testing and to try and clean up the fish water for them) then drain back in to the fish tank from the growbed. This will just be a temporary / testing system until I get my other growbeds up and running so I won't have a ton of money invested in plumbing yet.

I need to pick up a couple of smaller bulkhead fittings because I am going to put the filter on a stand with a drain in the bottom of it to be able to drain water to hopefully help remove solids that settle in the filter. We will use that water for watering the wicking beds / dirt beds. I figured a bulkhead fitting would be lower profile than the uniseal with a piece of pipe sticking through it so didn't order extra uni-seals for the drain out the bottom of the filter... but I can buy small bulkhead fittings locally, just not anyplace locally to pick up the 2" and up sizes so had to order them online (and I've never seen uni-seals locally.. looking on amazon and ebay people wanted as much for uni-seals as for bulkhead fittings but I did manage to find one place that was about half price finally and only took a couple days to receive them).

The 1" uni-seals that I bought I figured I would put as an emergency overflow in the fish tanks as a safety precaution in case the 2" SLO's are too small... but I think worst case I'll just turn the pump on a lower setting if the 2" can't keep up.

I need to stop and buy hole saws too because I don't have anything large enough for the uni-seals. Then I just need a little bit warmer weather on the weekends so I can spend some time working on building the filter and updating the plumbing situation. We are actually above freezing right now (38F, 3.3C feels like a heat wave after the last couple weeks... too bad I'm stuck at work).

I should have noted that I think part of the reason that the second 1" drain in my current set up is getting used at all is because I don't have enough cuts in my media guard on the main drain. I think if I put a few more cuts in it down low it would drop the water level down and never get close to the height of the second drain (the main drain I do not have a standpipe in, so the lack of cuts in the media guard and the stand pipe on the second drain is what is actually setting my water height in the GB). When I get my permanent GB's built I will fill them with water and test everything before I add media to the entire bed, that way I can make sure the drains function how I want and can adjust the media guards without having to remove all of the media.

I figured I'd make all four grow beds have exactly the same drain design to make it easier to build. The thing is though they all still act differently because the outflow from the siphons are all a little different because of how and where they are located. Where the siphons drain to seems to have a noticeable effect on whether or not they shut off or keep on dribbling.
I turned off all our grow-beds and put a five gallon bucket under the return line to the FT at the end of the pipe which snakes around to all the grow beds. That last valve is normally shut off. I can measure the outflow from the biofilters in the same way.

I can't remember if I posted this video in December of my tilapia...
https://youtu.be/nDw81bXAe3s



Here is a video of them today a little after a month later...
https://youtu.be/BwE0TNsIKxY

Those are growing pretty fast. They are looking good.

very cool. Maybe they'll be less skittish now they seen you up close.