Backyard Aquaponics
A place to discuss aquaponics

+1 Tom's idea, Just came to the same conclusion myself, though will be using flood and drain and two digital timers.

Actually solves an issue with only 17 programmable times on the digital timers as well. With my CHIFT PIST setup as long as I check the height the water comes up above the SLO when each pump is running I have a quick and easy visual on whether they are working ok.

Should one cack it I can just run the other longer until I get a replacement. Only thing I need to check is that the SLO can handle two pumps if both happen to run at the same time.

Yup and timers are cheap as chips... pretty reliable too

Some great info here, I had a failure the other day.

I found it when I switch the feeding light on, it did not work?

the pump had tripped the RCD, so all power to the system was down.

So it would be a good idea to have the backup pump on a separate circuit?

would be good if possible. All my GPO circuits in the house are on the same RCD so can't do that.

I've got a UPS for my AC air pump so having two pumps just adds another layer of redundancy. Makes me feel a bit more secure when away for 3-4 days at a time.

My system out the back has a dc pump (powered from a battery supplied by a homemade float charger) on a timer that turns over 60% water volume through 200L of media so if the power goes down that will run for a day or so.

I've had pumps and timers fail (had 4 mechanical timers fail hence using digital now), though so far no RCD trips or significant power outages from Western Power. IMO pump and timer failure are the most likely failure mode, followed by blocked/broken plumbing. The latter can be dealt with mostly using routine maintenance checks.

So people using 2 water pumps, do you have 2 sets of plumbing for the GB ?
I would find that a bit inconvenient to run 2 sets. Maybe an air pump is the best way..

Nope. Same plumbing from ft to gb. Easy to do with chiftpist. Dual pipes from sump to ft though.

Actually you could just have both pumps on the same plumbing to the fish tank. Have one at the end, then a backflow preventer then the second pump off of a T or Y. That should work.

You can set it up so that the water level in the sump is what activates the pump. Everything in my setup is CF except one or two beds that drain through a weep hole in the standpipe. Since I use a small sump, the water level rise that occurs if the main pump goes out would be enough to trigger the second pump. This is close to what I've been working on setting up for my power out backup but that uses a 12V pump instead of a regular pump and is triggered by a combination of no power and water level.

Be great if I could figure a way to combine these systems.

Are one way valves reliable in an ap system with all its biofilm etc? That would be my concern. Would not trust float switches much either, though maybe that's just me.

Re the Biofilm, good question and one I can't give you a definite answer on. Pump pressure should be enough to open the valves but I can't be certain. I think you'd actually need one backflow preventer for each pump not just the one as I suggested before.

I don't recall many issues with float switches but Joel and others who've used float switches in systems probably could tell you more. It was pretty common at one point here on the forum to see members using float switches in AP.

Check valves or one way valves are fine for AP but they create a large friction loss. They are also relatively expensive.

Two pipes going to the FT is the way to go if your FT is close to the sump. Two pipes going to a header tank and one pipe going to the FT may be more economical if your FT is further away.

Yeah I looked into the check valve thing a while back and they seemed expensive and there will be certain flow losses and another potential point of failure... if the reason for using them was to save money on plumbing the two pumps separately to the FT I could not see it being worthwhile worthwhile.

I had 2 pumps in my ST for a while (pumps to GBs), and used oversize (40mm on 32mm pipe) non-return valves to reduce friction losses. They were timer operated alternately to ensure at least half the pump cycles continued in the event of one pump failing.
The reason you need non-return valves is that these are not positve displacement pumps, and any pressure that is applied to the outlet side will cause water to flow back through the pump.

Important lessons I learned were that the 2 pumps need to be identical - mine weren't, although they were reasonably close in spec. However, because they weren't identical the different flow rates meant the taps on each GB had to be adjusted when changing over pumps, as the distribution of the flow was thrown out by the different water pressure/flow from the 2 pumps. So some GBs ended up not filling as much as desired when the Pondmax 8000 was on, but all filled at the same rate when the UP sump pump was running.
Lesson 2- the non-return valves ended up not fully closing, probably due to biofilm build-up, meaning that some of the pump output was flowing backwards through the other pump, when it should have been all going to the GBs. Mine are 40mm poly spring loaded type- I think the flap valve type may be better suited to the job.

You only need a non return valve if you are using the same pipe for both pumps. Another likely reason your NRV wasn't sealing properly is because it was a cheap one. Good ones that seal well and reliably cost $. I recently bought one that was 20mm and it was $22 I think. Ages ago I bought a 1.5" one for, I think, $50 odd. For those sort of dollars a second pump line to where ever you need it is pretty cheap by comparison.

The header tank option can also be cheap if the header tank is only a blue barrel or similar.

My pumps in the ST were: Pump |> T T <| Pump 2 parallel 32mm pipes, joined at far end to make a loop, T'd off 25mm pipe to each GB)

Needs 2 NRVs, otherwise one will leak water back through the other one, and one will be ok.



That may be a reason for some other ones failing, mine sure were not cheap! They worked perfectly well for a few weeks, before I had to start cleaning one or the other out every week or 2. If I try it again, it will be a flap valve, which should be more resistant to leakage due to bio film build-up.



Not when you have to replicate 8 ball valves and all the poly and pipe fittings- hundreds of dollars worth!

Sounds like mostly a no go for covering it with the same pipe. There may still be situations where it's the better option for one reason or the other, like space or barriers or cost.