Indexing Valves for Constant Height in Fish tank

I’ve had a few people ask about doing constant height in Fish tank systems with Aquaponics indexing/sequencing valves lately.

Doing constant height in fish tank (CHIFT) with an indexing valve does require a slight modification of thinking. There are ways to do it but I don’t think I would recommend doing it with only one pump. (It can be done but requires some complex plumbing and automated valves and probably isn’t worth it unless you really want to tinker with it to get it working properly.)

Why not just branch off from the pump to feed the fish tank and the aquaponics indexing/sequencing valve at the same time?
The reason is because the indexing valve requires a certain amount of pressure and flow to operate and if you T off to feed the fish tank before the indexing valve, you may not get enough flow/pressure to the valve unless you are very careful about choosing the pump and balancing the flow to the fish tank. I’ve not tried it this way so won’t guarantee it would work. Now if you are providing plenty of flow to not only flood the grow bed but be able to plumb back some of that to the fish tank it might work but sounds like a pain to me, extra plumbing and all.

What I would do is a spider CHTP (Constant Height two pump) system. Get one pump sized correctly to feed your sequencing valve and flood your grow beds in the time frame you wish. There are repeat cycle timers out there that can do what you want, they just cost more than the mechanical 15 minute increment timers. I’ve got one running 9 minutes on and 1 minute off so each of my six grow beds gets flooded once an hour. Then I would get a second pump sized appropriately to turn over your fish tank volume as much as you want and provide constant flow/aeration to your fish tank, I would even probably put this pump on the battery backup. Depending on the system configuration and the pumps in question, you might even have both pumps be the same model and then you could keep a spare as a backup that would work in either position if there were ever a failure.

As to the size of the sump tank for such a system. I would make it big enough to flood at least 3 or 4 of the grow beds at once (I am assuming flooding one grow bed per outlet of the indexing valve, if you are flooding more per outlet then the figures need to be for the entire outlet not per grow bed), this should give some leeway for pump height an a top up valve. Sizing the flow rate and holes in the stand pipes for this can be a bit of trial an error though. But I would expect that there are usually about two grow beds worth of water out of my fish tank at any one time on my 300 gallon system that is running the pump 9 minutes and one minute off. One grow bed is filled at the point the pump shuts off and the previous grow bed has usually drained about half way and other grow beds are usually still trickling for quite a long time. You don’t really want your sump to overflow if the power goes out and all grow beds drain completely.


12 comments to Indexing Valves for Constant Height in Fish tank

  • RupertofOZ

    Couldn’t agree more TCL, indeed looking at the “new” Chop2 design, the method you outline above is probably the only way it can realistically be done..

  • Hans Sparreboom

    Isn’t hard on the pump to stop and start? Wouldn’t it be better to use the timer to cycle the indexing valve?

  • TCLynx

    Depends on the pump. Some pumps are designed such that stopping and starting them a lot is really hard on them while other kinds of pumps don’t have those problems so much.

    The Indexing valve is purely Mechanical, it requires that the flow to it, start and stop in order for the indexing action to work. This can’t be done directly with a timer. It would require an automated valve.

    Now automated valves are possible but for an inexpensive irrigation valve to work, one would need a very powerful pump but there would be benefit of using the single pump to provide aeration to the fish tank as well as driving water to the solenoid valve and thus the indexing valve. But the added cost of electricity to run such a pump would probably negate the savings of perhaps not having to replace a little pump several years down the line and the solenoid valves are another possible failure point in the system and would need regular cleaning.

    Lower pressure automated valves are either going to cost much and still require a timer or you will have to design them yourself. I have done one of these but it still gives me regular issues in re tensioning the rubber bands when ever I have to replace them.

    Just seems simpler to do a smaller pump on a timer to me.

  • Pat Brown

    How important is it to keep a constant height of water in the fish tank?

  • TCLynx

    The water level in a fish tank does not need to be perfectly constant but it is important to keep the water level from fluctuating to the point that might stress fish too much and if a system were to pump a fish tank mostly dry, it is likely to kill the fish.

    For systems where a sump tank is a viable option constant height in fish tank is a really handy way to avoid the risk of fish tank being pumped dry by having the fish tank overflow at a constant height and the pump drawing water from a sump tank.

  • Pat Brown

    I’m just starting my system and have an 800 gallon fish tank and hope to flood 5 grow beds in sequence using an index valve. Each bed will hold a maximum of 115 gallons and will drain directly back into the fish tank. I figure the water will drop from 32 inches deep to approximately 28 inches deep when one bed is flooded. Will that much fluctuation make a difference?

  • TCLynx

    Pat, is that 115 gallons the total volume of the grow bed or the estimated amount of water needed to flood the bed?

    If the water fluctuation is only 4 inches in a tank that deep, I wouldn’t worry at all. I’m running a fish tank that is total possible depth of fish tank 25 inches and therefore the normal water depth of the fish tank is less and the water fluctuates lower that that. Fluctuating around 30 inches sounds very good to me.

  • Pat Brown

    That is the estimated amount of water to flood the bed.
    I just placed an order for a 11/4 indexing valve from you and have been undecided about the pump to use. As I said, the tank is about 800 gallons and about 32 inches deep. The grow beds will be about 48 inches above ground. I was thinking about the Danner 2400GPH Mag Pump.
    What do you think?

    • TCLynx

      Ok that sounds good. That also tells me which stem disk to include with the indexing valve. The Danner 2400 GPH pump should work fine for the pressure needed to operate the indexing valve. I know some one operating one with the Danner 1800 gph pump so the 2400 should allow you to flood quickly.

  • Pat Brown

    Thanks for the info. I now need to find a dependable timer to do the job 24/7. Any advice for me there? I appreciate your helpful assistance in this new adventure for me.

  • Andrew Smith

    I realize this thread is quite old. I set my timing by the size of my sump tank which is the same water volume as my beds and a float operated sump punp.

    1.Initally I added water to all the beds until they start draining.(all drain back into the fish tank)
    2.Add water to fish tank until it overflows into the sump.
    3.When the sump pump is triggered it opperates the indexing valve and pumps the volume of water that is in the operation range the sump then turns off.
    4.Keep adding water to the sump until the sump pump triggers again this provides a buffer against loss due to leaks and evaporation.

    In hot weather check that your pump is triggering an a regular basis and there is a steady flow from the beds to the tank.
    The sump can also act as a flood and drain bed for crops that do not mind wet roots.
    I also have a NFT system between the overflow and the sump.

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