Reverse DWC

Rahz said:

There will be a single 1/2 inch supply and 2 or 3 returns, so I'm going to try 3/4 inch returns first and see how it goes. And yes, your system is exactly what I'm talking about. Good to see it's been put into action.

Click to expand...

2 or 3 returns and I think you'll be fine. Please post results if you try it that way, I would love to use smaller lines.
I think the size of the pump is going to be a key factor. The water is only going to move through the return lines at a certain speed because it isn't being pushed by a pump. So you really want a smaller pump size than what the returns can handle, obviously I guess. I'm only saying this because I've seen a lot of guys using huge gph pumps in their rdwc's that would be way too much force for this type of setup.
Good luck

Airwalker16 said:

Rahz, you gave me so much great advice that saved me headaches when I was learning. Please take my word and use AT LEAST 1" To start, so you'll only have to go to 1.5" when you see its not enough.

Click to expand...

I appreciate the consideration. If 3/4 tubing is overwhelmed my first thought would be to use a smaller pump. I don't want to save tubing or PVC between grows so 3/4 makes more sense. We'll see how it goes.

Another idea I'm having, to avoid building a manifold and using more tubing would be to do a circuit path but have the input at the bottom of each grow bucket and output at the top. Pump get's dropped in the rez and feeds the first grow bucket. This would have only one outlet after the pumps inlet so it might be more prone to run into flow problems, but there again, it's just a matter of getting the flow volume right. I don't want to wait hours to be able to check the PH in the rez after adjustment so that would be one consideration. I think there's probably a benefit to having higher GPH through the buckets so that's another consideration. Back before I took a break from hydro I was doing waterfall DWC with high flow rate and getting 1.5 GPW. Currently with just the gravity feed and no PH adjustment's it's between 1.25-1.3 GPW. I suspect a lot of that is the PH issue I will be solving with recirculation, but in theory it seems like the more water flowing through the roots the better.

2WorldsFrog said:

2 or 3 returns and I think you'll be fine. Please post results if you try it that way, I would love to use smaller lines.
I think the size of the pump is going to be a key factor. The water is only going to move through the return lines at a certain speed because it isn't being pushed by a pump. So you really want a smaller pump size than what the returns can handle, obviously I guess. I'm only saying this because I've seen a lot of guys using huge gph pumps in their rdwc's that would be way too much force for this type of setup.
Good luck

Click to expand...

Agreed, and I'll post an update once it's running.

I'm willing to consider using pumps again because I've been having great success with beneficial microbes. When I was trying to run sterile I had issues that were hard to clear up and would reoccur in new equipment. I would soak the chiller and pumps in heavy bleach water to no avail... probably not good for the equipment either. I'm thinking with beneficial bacteria contam issues won't be a concern with pumps, but I'm wondering if there will be buildup issues. I'll probably just rinse between grows or soak in a light bleach solution. Any thoughts on this would be appreciated.

All I can say, is I had 6X 5gal buckets EACH with their own 1" return to a res, and that pump drained that fuckin res in 15 seconds flat.
Once I got 2", on 8 buckets and all connected together 4&4, 2 inlets, you can't even tell the waters being pumped out. It flows back so well that the water level stays completely still.

Airwalker16 said:

Rahz, you gave me so much great advice that saved me headaches when I was learning. Please take my word and use AT LEAST 1" To start, so you'll only have to go to 1.5" when you see its not enough.

Click to expand...

lol,I think he means using 3x 3/4.So Using what he has I assume.

Airwalker16 said:

All I can say, is I had 6X 5gal buckets EACH with their own 1" return to a res, and that pump drained that fuckin res in 15 seconds flat.
Once I got 2", on 8 buckets and all connected together 4&4, 2 inlets, you can't even tell the waters being pumped out. It flows back so well that the water level stays completely still.

Click to expand...

I think I can make 3/4 lines work, but I'll put some thought into what you're saying. I would like to have a high flow rate, or at least know for sure how much of a difference it makes. I have several stations so I will probably try higher flow in one to compare at some point. And if I can't make the 3/4 work, you told me so.

The pump I'm going to start with is 293 GPH. Split between 4 buckets that's only 1.2 gallons per bucket per minute, so one exchange every 4-5 minutes. If I go with the inline circulation I mentioned I could get by with a 100 GPH pump or less and get similar flow.

Being able to adjust the PH and check it a couple minutes later would be nice.

Rahz said:

Being able to adjust the PH and check it a couple minutes later would be nice.

Click to expand...

I did a food coloring test in plain water with the 250gph pump after everything was set up. Within 5min. there was color in every bucket, and it took 30min. for all of the water to be a uniform color throughout the buckets and res.
30min. goes by pretty quick for me in the garden, it's mostly smoking bowls and daydreaming, but I'm familiar with my nutes/up/down so I can adjust things and basically walk away.
Faster would be cool, I just haven't needed it yet.
Here's a few from a 5wk veg, day 11 from flip in my 4x4. 1 before defol, the rest after.

Fwiw my opinion is if your getting 10x the volume of the sites (not system) turnover an hour any more is not necessary but also not harmful to a point. More than adequate for stable ppm, ph and o2 levels. I see people running huge gph and just kinda shake my head at the more is better concept because that's only true to a certain point. Of course you need to take head pressure into account but imo most systems are way over done.

I also agree a live system with beneficial bacteria, fungi and or enzymes (which bacteria produce) provides a much healthier plant far more resistant to infection.

Ph swings I feel there are 2 main considerations. The larger the quantity of water in a system the more stable. The other option is increasing the buffering capacity and using more acid. This will help to a point but can start giving negative effects at a certain point and you need to really do some calculations in order to make sure your not throwing the nutrients ratios to far out of whack.

Another major consideration for a new system is adequate gas exchange. It's not so much the temps that are important as anything under 80f has enough DO for our needs. I find 72-74f to show a significant difference in growth over 65-68f. The important part is enough surface agitation to replenish o2 and keep it near saturation levels for the given temp. Sorry to anyone who buys into water temps causing root rot it's just not the case. It does however speed up the reproduction and metabolic rate of almost all bacteria etc so things can go wrong faster but in a healthy system all your going to see is faster growth.

Just my 0.02 take it or leave it. Hope this works out for ya

So the 293 GPH pump is a bit too much for four 3/4 inch lines. I've used clamps to close up the feed lines and have the system stable. You were right @Airwalker16 I could probably get by with a 150 GPH pump.

I don't really like all the extra tubing. This is replacing a gravity feed system that uses a 1 foot section of 1/2" tube for each bucket.

I'm going to use it for a run but will be considering alternatives for my next grow. Might go back to tubs. Only drawback with them is they need about 10 gallons more per plant.

Another idea I just had...

So I decided I didn't like it, tore it down and put my gravity feed system in place. I thought if I could put one tiny pump in the rez feeding to a grow bucket I can recirculate and basically keep the same system. I did a search and see 40-50 GPH pumps for $8 each, so I think that's what I'm going to try. Less than a gallon per minute I shouldn't need to worry about the grow buckets overflowing. This will let me adjust PH in the rez which is all I really wanted to accomplish.

I just ordered a couple 50GPH max pumps, 3 watts each, adjustable water flow. I'll update when I have some results.

Tiny pumps have been installed. They seemed to have equal pumping capacity. I was worried they would be cheap and water flow would be hit or miss but it looks like they will be consistent. At full flow a single pump was changing the water level up in the rez, low in the grow bucket. They have 4 flow settings via a small toggle switch. I selected the 2nd lowest and took some measurements. At this setting each pump moves 10 GPH and water level is stable with 1/2" tubing from rez to grow buckets.

I'm going to play around with them like this for a while, maybe not make any changes. The flow is low but it will allow me to adjust PH in the rez. If I check it a couple times a day I should be able to keep the PH right where I want it and after a week or two I should be able to get a better guess at how much adjustment is needed and adjust once a day. If the low flow starts bothering me I can always switch to 3/4" tubing.

I tested the wattage, hoping that the 10 GPH would use substantially less power that full flow. These pumps are listed as 3 watt units. At full power they are using 3.9 watts. When turned down to the 2nd lowest setting they use 3.7 watts, so not what I was hoping for. My water stays at a consistent 70 degrees. I'll check it tomorrow and see how that changes. I don't know how quickly heat will dissipate from the buckets but I did some math and found they will raise the temp of the water about .5 degrees Celcius per hour so I think it will be fine. As long as it doesn't climb past 72-73F I'll be okay with it.

So there you go. Temp test pending but other than that I'm really happy with the tiny pumps.

I'm not measuring any temperature increase. It's actually a degree lower in the rez.

The new 50gph pumps have arrived. They don't have as much flow control as the first two I ordered so I'm turning them on to check and adjust PH. Takes about 15 minutes. I'll be converting the gravity feed tubes to 3/4" on all my buckets eventually. I've already got one system set up that way and can run the pumps at 30-35 GPH without a change in the water level.

I'm using them in the grow buckets so remains to be seen how well they'll handle roots, but it should be easy to clear the roots if it becomes an issue. I considered running them from the rez but that would put the roots in a position to grow into the feeder tubes.

Very happy with this solution. I used to grow in tubs, 2 plants per tub and got REALLY good results. Plenty of room for the roots, port to check and adjust PH. Only issue was that it required about 2x the nutrient solution as the bubble buckets. Hopefully this will put me back on my game. If anyone is interested in these tiny pumps, they can be found on Amazon for 7-8 bucks each. They disassemble down to the motor casing so should be a snap to clean between grows.