Backyard Aquaponics
A place to discuss aquaponics

Hi Taz

No float switches required in my system, the pump runs 24/7 but other do use them. I have a large sump that holds nearly double the amount of water needed to fill my grow beds so it cannot run dry unless I forget to check it. I don't have the issue of freezing so I have not considered it. Others may be able to help you on that one

On the pump issue, mine is a Laguna, very cheap to run, about $100.00 a year 24/7.

Taz, I've had the water freeze coming out of the pipes, but never the top of the tank (and it gets pretty cold in Canberra). You can always put a second overflow that goes back down to the sump. Means that whenever the water level rises just that little bit too much (for whatever reason) you don't lose all your water out the top of your tank. Just put it slightly above the outlet to your growbeds.

+1 on the second overflow.
If the overflow to the growbed blocks up or even slows the water in the FT will rise and could even overflow. A second overflow back to the sump means that the pump should always have water unless there is a blockage in the syphon from the growbed.
An overflow from the growbed that takes water back to the sump if a syphon blocks is another good idea and this will solve 95% of water loss issues. The other 5% being broken pipes and holes in tanks/GBs

Thanks gemmell, yeah I might do that in anticipation of a long sub-zero night. It could save me the heart ach later on.

How do you guys go about throttling back your pump so that the inflow into the FT isn't that great that it will fill up quicker than what is being let out to the GB's? Having no experiance yet with pumps, pipes and flow rates and the sort I'm thinking there may be a chance that you overflow your FT purely by too much inflow (especially if pumping for 15min.) and not enough outflow? Or isn't this a factor when your using 90mm pipework from your FT? Do you place a tee in the line and run a tap into the FT for control and plumb the excess back the sump?

Thanks guys, Taz

My pump actually has a little thingo you can turn to throttle back the flow rate. Otherwise, the standard T with tap would work. You tend to find that 90mm pipe is going to accommodate a large volume of water - unless you've got a MASSIVE pump, the water should flow out as fast as it flows in. Put it this way, my 3000L an hour pump comes in using 20mm pressure pipe. The SLO is 50mm pipe. I find that the water level rises almost to the top of the outlet, but never gets any further. I think this is more the delay introduced by the SLO than anything else.

Taz what i was trying to say was that you don't need to throttle it back if there is a second overflow back to the sump. I have 5000l/hour going into fish tank but only about 3000l/hour goes into the growbed and the rest goes through the top overflow back to the sump where it splashes down and get pumped back into the tank this way the tank gets heaps of DO and i don't have to adjust/throttle back anything. If the GB feed blocks then more water just goes back to the sump and it can't ever overflow.

i doubt throttling back on a pump is very good for them unless of course they already come with a thingo to do the cutting back

TCL helped me realize i do not need as much head height as i thought i did so im now thinking continuous flow

its about 7m from FT to sump and right at 1320mm combined height from base of sump to inlet at FT so i can go with smaller pump thanks to this discussion and TCL

Yep, head height is the elevation not the distance, thought running water through really long pipes will add some resistance which will affect how much water it can pump but running 7 m of pipe up a slope is not the same thing as running 7 m straight up.

You should not throttle back a pump or restrict the pump inlet or outlet, it is hard on the pump and a waste of power. You should base you pipe size on what the pump wants and then size your other piping to handle the flow rates you will have.

I see one drawback of having an overflow from the fish tank back to the sump tank. If you do that, you wind up with solids going into your sump tank without being filtered by the grow beds. I agree that it is nice to have extra flow for aeration to the fish but one of the major benefits of the CHIFT PIST design is the "pump clean water" thing. As soon as you introduce unfiltered water back into the sump, you can't simply split off from your pump feed to towers of NFT troughs. Just something to think about before falling back on such an overflow in a design. You might be better off having the larger pipe going to the grow beds or the overflow going to the grow beds and make sure the grow beds have an extra overflow to handle the added water flow as needed.

Thanks FF, your right that's a lot simpler and better for DO too. That solves all the freezing then overflowing problems.

TCL, as far as overflowing solids back into your sump from the FT I would have thought there'd be very little solids floating around at the top of the FT, unless the inflow from the sump stirs it back up again?

Fish can stir up solids, inflow can stir up solids but the primary thing likely to flow from a fish tank overflow into the sump, would be floating fish feed, leaves, and any plant material you might through in for the fish (duckweed, or greens.)

No leaves make it through the mesh on the top overflow. It also has an elbow on it so the water is taken from 40mm below the surface. Also because my tank swirls the water any crap goes to the centre drain at the bottom and any floaties would stay spinning in centre at top. So I would have to say nay to dirty water making it to the sump. I don't use floating food but if i did i'm sure it would still work. The benefits of the second outlet far out weigh any potential problems.
I pump 24/7 and if I didn't want to flood the growbed at night to help with temps, i could just turn off a tap conected to the bottom outlet without any hassle. Fish still get DO and water still circulates how can this be a bad thing?

Oh and should you want to waste electricity and throttle back a pump you can but only with a magnetically driven pond pump as the magnetic drive works like a clutch in a car. A pump like a pool pump will burn out and die if it is stopped completely but a mag drive will just use the electricity and not move any water. Can someone back me on this one?

Technically, yes, but deadheading a pump is never good for it, and not recommended.
Sure it will just use more power, but using more power means more heat dissipation, as the power is not going into moving water, but overcoming friction.
of course for pool pumps etc, it is disastrous, as they aren't covered in water, assisting cooling.

You are not stopping it completely as long as there is a bit of water flowing its just like pumping to max head as for the mag pump slowing down the flow would make it use more power but only miniscule amount like $10 a year

You would never dedhed a pump on purpose but if it got jammed on something a mag pump is just going to chew electricity and not die on ya. A bypass is a far better idea than a throttle and a timer is an even worse idea.