Pump Flow

[GpsFrontier]

Ya, I can see how that wouldn't work if you were trying to divide the water flow to both tubs evenly. I have a couple suggestions, but first I want to ask a few questions:

1. What is the lower solid line between the too tubs and reservoir supposed to be? Is that supposed to be a return line?
2. Also are these tubs supposed to have water in them all the time?
3. Is the water level in the reservoir supposed to be the same level as in the tubs? Or is the reservoir actually lower than the two tubs?
4. What kind of system is this supposed to be (a recirculating water culture system, flood and drain system, NFT system etc.)?
5. Do you have an overflow tube to keep the water from overflowing the two tubs?

[MickR33]

Very good questions you have, ok the botton lines between the tubs are 32mm piping that connects them all together so the water level is always the same in each tub and resivor are are even, so the 19mm top tubing is just used to circulate the water to the tubs from the resivor to keep it fresh, and yes there is always water in them. The setup actually has another tub on top of tub 1 and 2 that has rockwool slabs in then and the bottom of those tubs is like a mesh so the roots and water can come out the bottom into the bottom tubs, i have another pump with another 19mm tube running to the top tubs that had little drip tubes feeding the plants.

[GpsFrontier]

OK, I wasn't sure but I thought that might be how you have it set up. What you have is a recirculating water culture system. I can see two simple ways to fix your problem. The first is to change your T connection around like I show in the first attachment. That will equalize the pressure to both sides. Try and keep the length of tubing to both sides/tubs close to the same length. They don't need to be exactly the same, but you don't want one side 8 inches long and the other side 3 feet long.

The other option that I show in the second attachment is to simply bypass the middle tub altogether. If you pump from the reservoir all the way to tub 2 bypassing tub 1, all the water still needs to pass through tub 1 to get back to the reservoir. Making one continuous circulating loop.

Either way there may be the possibility of the tub's overflowing if the return tubes (32mm piping) cant handle the amount of water volume your pump is putting out. I realize your return piping is almost twice as big, and that's great because it needs to be. Even if you haven't experienced it backing up so far, once you change it, you may get more water volume from the pump than you did before. So you just want to keep an eye on it for an hour or two, and if it doesn't start backing up by then, it wont unless your return lines somehow get clogged with debris.

If it does start backing up just reduce the water volume from the pump. Either by a adjusting a valve on the pump if it has one. Or install a ball valve in the water feed line from the pump to the tub's and close it off some.

[MickR33]

wow thats very good information and superb diagrams, what i didnt add in the picture was that there is also a 32mm pipe going from tub2 all the way back to the resivor as well so it is like a big loop. I like your idea about putting a t at the pump and running 2 hoses so that way it should split it evenly, what about if i turned the t on tub1 upside down and so the hose is facing upwards and then bending the hose around and pointing down, im using the very fexable black hose so its not the stiff type, that way the water would have to push upwards to get it into tub1 and it should get the pressure by the time its flowing into tub2.
Thankyou so much for your reply you are very helpful and i aopreciate it mate

[GpsFrontier]

what about if i turned the t on tub1 upside down and so the hose is facing upwards and then bending the hose around and pointing down

Then you will have the same problem, just with the other tub. Water takes the path of least resistance. Even if you had lots of pressure from the pump, the water will fallow the low path.. That's exactly why the water went in tub 1, and not tub 2. Even though your T connector was set so there was a straight line going to tub 2, the side going to tub 2 was facing down, and water flows down hill. Even if you turned it sideways so both outlets were level, you will have uneven water flow because water takes the path of least resistance. It will fallow the straight path before it turns a 90 degree corner. That's why you need to change how the water goes into the T connector to equalize the pressure. So both lines going to the Tub's (1 and 2) need to take the same 90 degree turn to get it to work.

The only way to get the water to flow uphill that way is if the line from tub 1 to tub 2 is smaller than the line from the pump going to the T connector, thus causing back pressure between the pump and T connector. But good luck getting it to flow evenly that way, you'll still likely wind up with one side getting more water flow than the other. You may be able to do it if you install a ball valve between tub 1 and tub 2 so you can adjust the size of the opening the water can flow to going to tub 2. But all that time, effort, and extra parts just make it more complicated for no reason.

Just remember the two rules,
1 Water flows down hill
2. Water will fallow the path of least resistance

what i didnt add in the picture was that there is also a 32mm pipe going from tub2 all the way back to the resivor as well

So if I understand correctly, the 32mm return pipe from tub 2 does NOT go through tub 1 on it's way back to the reservoir. Instead, you have one 32mm pipe from tub 1, and one from tub 2 each going back to the reservoir separately. So each tub has it's own direct return back to the reservoir. If that's the case the second option I gave you wont work because you don't have the return going through tub 1.

If I have it wrong and do have it like you drew up, but mean you also have a second return from tub 2 that runs directly back to the reservoir as well as the one going through tub 1. You can cap off the one from tub 2 going directly back to the reservoir, thus diverting it and forcing all the water to flow back through tub 1 on it's way back to the reservoir like intended in the second option I gave you.

[MickR33]

Thankyou for such a quick and helpful post again, yeah the tubs are all houned together with 32mm hose like in the photo i just added, thats a top view obviously and thats just for the bottom layer, tub 1 & 2 have another tub on them with a rockwool slab in it like in the other photo i just added. Yes i see what you mean about water following the path of least resistance, it will only goto tub1 and when i want i just block the hose on tub1 to get it to flow to tub2, but im going to just add another pump and hose so the reservoir will have a direct pump going to tub1 and another one going straight to tub2. Any idea how fast i want the pump to be pumping into the tubs to circulate the nutrient solution? the tubs are 45ltr ones i think and the pump i have at the moment i think is just a 350ltr an hour pump and i have it turned to maximum.
Thankyou so much for your time mate.
I also have a few questions about the drip feed if your up for it lol

[GpsFrontier]

Hello MickR33,
You can use two pumps if you want, but for me that's waste. Not only is it a waste of electricity running two pumps instead of one to do the same job, doubling the electrical cost. But it's also a waste of materials. Instead of having two pumps tied up in one system, two pumps could be running two different systems. If you designed it like in either option I gave you, there would be no need for a second pump.

Any idea how fast i want the pump to be pumping into the tubs to circulate the nutrient solution? the tubs are 45ltr ones i think and the pump i have at the moment i think is just a 350ltr an hour pump and i have it turned to maximum.

There isn't any real defined standard for circulating water or air. Circulating more or less just means not remaining still/in one place. But I typically use a standard rule of thumb "1 hour" for calculating circulation. Meaning to circulate the entire volume in 1 hour. For water once an hour, for air 5 times per hour. Here your circulating water, so I wont go into calculating for air. You say your tub's are 45 liters (about 12 gallons) each. So I would want circulate the entire 12 gallons through the system every hour. You have 2 tubs for a total of 24 gallons to circulate each hour.

You said your pump is rated for 350 ltr (about 92.5 gallons) per hour. Normally you would need to take into consideration Head Height (the back pressure/weight from the water when pumping it above the water line). But because of how you have the system set up, your not needing to pump it more than one foot above the water line. So the head height doesn't really come into play here. So assuming your using the maximum size tubing the pump is designed for and not otherwise restricting water flow from the pump, your pump should be able to put out around 92 gallons per hour. 46 gallons (173.8 ltrs) per hour to each tub.

In other words, the way you have the system set up, and with the pump you have. That pump is capable of circulating the entire water volume of both tubs more than 3 times per hour (3.83 actually). There will be some natural points of restriction of water flow from the "T" and elbow connector's etc.. But their minimal and you don't have many. So even rounding down from 3.8 times per hour to 3 times per hour to compensate for the "T" and elbow connector's. That pump is more than capable of providing enough water circulation if set up right.

P.S.
Ask anything you have questions about, that's what the forum is for.