Backyard Aquaponics
A place to discuss aquaponics

I've just hooked up another set of GBs about 1m higher than the initial GBs. I'm having a little bit of trouble regulating the water flow. All beds have taps on the end of the irrigation running to them, and I'm adjusting them to regulate.

Sometimes, no water at all reaches the upper beds, until I close all the lower taps. Once the top is running, I can turn the lower taps on again, with differing degrees of success. All in all, it's a bit fickle for my liking.

Is this a fundamental fluid dynamics issue?

I'm thinking about different soultions, including using a solenoid to pump alternatively to the top and bottom GBs, or perhaps even pumping to the top beds and having them drain into the lower beds before the water returns to the FT.

Any ideas?

Is this a fundamental fluid dynamics issue?

I think so ryan, but others will confirm...
My system, the most distant GB has the G/valve
open considerable more than the others...
Friction loss for me.

Could be your pump just doesn't have enough head. The other issue can be how the piping is run and there may be air trapped blocking flow. One way to deal with this is to use a head tank that is higher than all of the trays. You then drain from the head tank to any of your trays.

Good idea, except I'm trying to keep the weight down on the back deck where the upper growbeds are.

The pump is suited for the head height, however one thing I never factored in was running at 2 levels. Top GBs would be about 2.5m and the lower GBs about 1.5m above the pump. The pump is 6000lph @ 70w. Perhaps a bigger pump is the easiest solution.

If I did get a bigger pump, I would consider one with a float switch to ensure it never runs dry. Any suggestions on suitable pumps would also be helpful.

If the pump is capable of the head why not try running the pipe to the top bed, no tee offs then tapping off on another pipe which is the return to the lower beds.(worth a go anyway)

To make this clearer, perhaps .
Pipe from pump to hight of top bed 90 degree bend. Pipe running towards top GB Tpiece pointing just up off vertical to 90degree bend (your flow to the bottom bed). Water goes from pump to tap on top bed closing this gives you a header to flow water up T piece and then down to bottom bed. Control is then mainly on the top bed tap.

Hi Ryan:

I had two tiers of beds, and made a thing that looked kind of like goal posts using tees to split the flow. It has to be pretty level but worked for me. To minimize leveling inaccuracy make the segments off the tee as short as possible, so that the flow doesn't try to go to one side exclusively.
HTH!

Thanks Dave - does it matter that all the watre is being pumped to the maximum height? I was thinking it would be more efficient to pump as little as possible up to the higher GB, hence I have mine splitting at the level of the lower GB. I'll take some photos this aftrenoon to help explain.

Pumping and efficiency is way overblown. If a pump isn't running at max design flow it wastes most of the energy. The best design it to run the pump at otimum design flow and then shut it off. If you set up for flow to the top bed and give it extra flow so it can supply the lower beds, the energy cost will be minimal. Throttling flow costs more energy believe it or not.

If you want to stick with what you got, I agree with those saying to lift the piping for the lower growbeds to match the top beds just to make the fluid dynamics of it all a bit simpler to cope with.

Or, you could let the top beds cascade into the lower beds which could mean a bit less fluctuation in the fish tank normally (provided you don't wind up with them all flooded at the same time anyway for whatever reason, which can always still happen occasionally so plan accordingly.)

The issue with solenoid valves is that they are generally meant to deal with very clean water and an AP system is likely to gunk them up and require more maintenance than most of us really want to mess with on such a regular basis.

Good luck!

I think I got it sorted. After some adjustments this afternoon, it now appears all GBs are filling in about 12-13 minutes - within the 15 minute increment on my timer. If I remove some of the elbows and replace them with curved poly, it might become that little bit more efficient and fill that bit faster. I might also experiment with pushing all the water to the top GB level and divert it at that height between the 2 levels. I'll keep you posted.

Thanks everyone for the advice and comments.

BTW, photos should be up in my system thread soon

I use a 2in main pipe and have the GB feed from this. At the end I have whats left go to a higher swirl tank and 200ltr bio-ball filled return to the tank. I use taps on every outlet before this to control flow.

I'd only send the water that you need to up high - why push it all up there when you dont need to?

That's exaclty what I thought when I set it up. Currently, the split is at the same level as the lower GBs. Whilst it's working at the moment, I'm not too concerned

This does seem like the logical thing to do, but, all the water would rather stay at the lower level of course. To divert some water up higher from the lower level, you have to restrict the water at the lower level and any fluctuation in pump flow or that restriction can send everything out of whack, especially if you are operating at or near your pump capacity. Gets really fiddly to keep balanced.