Hey guys,

So this has probably been done but I couldn't find anything.

I thought of a simple way to automate feeding to keep steady ppm and ph values with use of a fertilizer feeding tank above the reservoir connected to a float valve.

I guess it can be used in any hydro system but I will use a RDWC here as an example.

Please excuse the crude drawing.

So we see here FT is the fertilizer tank, R is the reservoir and B1-4 are the buckets.

The fertilizer tank feeds into the reservoir when the water level drops.

Basically we are going to measure how much water and fertilizer the plants use to calculate how strong to make our nutes in the fertilizer tank.

It would be best to dilute your ph down so that 1 drop of ph down drops the ph of 1 liter of res water by 1 ph.

First we need to know how much water is in the RDWC system (reservoir + buckets).

Starting with an empty system, measure how much water you use to fill up the res and buckets making sure to fill the last bit from the fertilizer tank so as not to submerse the ball valve beyond the shut-off level. In this example the res + buckets hold 100 liters.

Next, add your nutrients to your desired ppm and adjust ph taking note of the ph before adjustment and how much ph down you are using to get to your target ph. In this example we will make a 300ppm solution and add 100 drops of ph down to adjust from 6.8 to 5.8 ph.

Now fill up your fertilizer tank with water, taking note of how much you put in and then measure the ppm. In this example I will be using water that reads 60ppm filled up to 40 liters.

Now that we know all the different numbers going in, we wait. Say we leave the system for 4 days (could be any number of days, as long as there is a significant change in ppm) and come back to see that 10 liters have been depleted from the fertilizer tank. We then check the ppm and ph in the reservoir. Lets say the ppm is at 250ppm and the ph is at 6. Take a note of that and adjust the ppm and res back to 300ppm and 5.8 ph.

So we saw that the ppm has dropped by 50ppm and the ph has risen by 0.2.

PPM

To calculate how many ppm we should increase our solution in the fertilizer tank by, we take the rise in ppm (50ppm) times the volume of water in the system (100L) divided by the volume of water depleted from the fertilizer tank (10L).

So 50 x 100 / 10 = 500ppm is how many ppm we have to increase the solution in the fertilizer tank by.

Our fertilizer tank currently has 60ppm water in it so we add nutes till we are up to 560ppm, then ph to 5.8.

PH

To calculate how many drops of ph down

So 0.2 x 100 / 10 = 2 drops of ph down per liter is how much we have to increase the solution in the fertilizer tank by.

Our fertilizer tank currently has 0 drops of ph down in it, so 0 + 2 = 2 drops per liter

Our tank holds 40 liters so we will need 2 x 40 = 80 drops of ph down.

Now if the plants keep feeding at the same ratio of water to nutes, all you have to do is refill the fertilizer tank with a nutrient solution at 560ppm and 2 drops of ph down per liter and your res should stay at 300ppm and 5.8ph indefinitely.

Your plants may start changing their feeding habits though, so lets say you go check on them a week later. There are 12 liters gone from the fertilizer tank,the res is at 280ppm and your ph is at 5.9.

Write those numbers down and then adjust the ppm and ph in the res back to 300ppm and 5.8ph

Now we do the same calculation again:

PPM

Drop in ppm (20ppm) times the volume of water in the system (100L) divided by the volume of water depleted from the fertilizer tank (12L).

So 20 x 100 / 12 = 167ppm

That is how many ppm we have to increase the solution in the fertilizer tank by.

So 560ppm + 167ppm = 727ppm is our target ppm.

PH

Rise in ph (0.1 ph) times the amount of ph down needed to drop the res ph by 1 ph (100 drops) divided by the volume of water depleted from the fertilizer tank (12L).

So 0.1 x 100 / 12 = 0.83 drops of ph down per liter is how much we should increase it by.

So 2 drops + 0.83 = 2.83 drops per liter, so for a 40 liter tank we would need 113 drops.

28 x 2 drops = 56 drops

So the total amount of drops needed to get to 113 drops would be 113 - 56 = 57 drops.

---------------------------------------------------------------------------------------------------------------------

Dunno if I explained this in a way that normal people can understand... but yeah, this should keep ppm and ph really steady and drastically reduce the amount of times you need to check on things.

I wrote this in kind of a rush so let me know if I made any mistakes or if the whole thing even makes sense lol

So this has probably been done but I couldn't find anything.

I thought of a simple way to automate feeding to keep steady ppm and ph values with use of a fertilizer feeding tank above the reservoir connected to a float valve.

I guess it can be used in any hydro system but I will use a RDWC here as an example.

Please excuse the crude drawing.

So we see here FT is the fertilizer tank, R is the reservoir and B1-4 are the buckets.

The fertilizer tank feeds into the reservoir when the water level drops.

Basically we are going to measure how much water and fertilizer the plants use to calculate how strong to make our nutes in the fertilizer tank.

It would be best to dilute your ph down so that 1 drop of ph down drops the ph of 1 liter of res water by 1 ph.

**SETUP**First we need to know how much water is in the RDWC system (reservoir + buckets).

Starting with an empty system, measure how much water you use to fill up the res and buckets making sure to fill the last bit from the fertilizer tank so as not to submerse the ball valve beyond the shut-off level. In this example the res + buckets hold 100 liters.

Next, add your nutrients to your desired ppm and adjust ph taking note of the ph before adjustment and how much ph down you are using to get to your target ph. In this example we will make a 300ppm solution and add 100 drops of ph down to adjust from 6.8 to 5.8 ph.

Now fill up your fertilizer tank with water, taking note of how much you put in and then measure the ppm. In this example I will be using water that reads 60ppm filled up to 40 liters.

**MEASUREMENT**

Now that we know all the different numbers going in, we wait. Say we leave the system for 4 days (could be any number of days, as long as there is a significant change in ppm) and come back to see that 10 liters have been depleted from the fertilizer tank. We then check the ppm and ph in the reservoir. Lets say the ppm is at 250ppm and the ph is at 6. Take a note of that and adjust the ppm and res back to 300ppm and 5.8 ph.

**ADJUSTMENT**So we saw that the ppm has dropped by 50ppm and the ph has risen by 0.2.

PPM

To calculate how many ppm we should increase our solution in the fertilizer tank by, we take the rise in ppm (50ppm) times the volume of water in the system (100L) divided by the volume of water depleted from the fertilizer tank (10L).

So 50 x 100 / 10 = 500ppm is how many ppm we have to increase the solution in the fertilizer tank by.

Our fertilizer tank currently has 60ppm water in it so we add nutes till we are up to 560ppm, then ph to 5.8.

PH

To calculate how many drops of ph down

**per liter**we should increase our solution in the fertilizer tank by, we take the rise in ph (0.2 ph) times the amount of ph down needed to drop the res ph by 1 ph (100 drops) divided by the volume of water depleted from the fertilizer tank (10L).So 0.2 x 100 / 10 = 2 drops of ph down per liter is how much we have to increase the solution in the fertilizer tank by.

Our fertilizer tank currently has 0 drops of ph down in it, so 0 + 2 = 2 drops per liter

Our tank holds 40 liters so we will need 2 x 40 = 80 drops of ph down.

**RE-ADJUSTMENT**Now if the plants keep feeding at the same ratio of water to nutes, all you have to do is refill the fertilizer tank with a nutrient solution at 560ppm and 2 drops of ph down per liter and your res should stay at 300ppm and 5.8ph indefinitely.

Your plants may start changing their feeding habits though, so lets say you go check on them a week later. There are 12 liters gone from the fertilizer tank,the res is at 280ppm and your ph is at 5.9.

Write those numbers down and then adjust the ppm and ph in the res back to 300ppm and 5.8ph

Now we do the same calculation again:

PPM

Drop in ppm (20ppm) times the volume of water in the system (100L) divided by the volume of water depleted from the fertilizer tank (12L).

So 20 x 100 / 12 = 167ppm

That is how many ppm we have to increase the solution in the fertilizer tank by.

So 560ppm + 167ppm = 727ppm is our target ppm.

PH

Rise in ph (0.1 ph) times the amount of ph down needed to drop the res ph by 1 ph (100 drops) divided by the volume of water depleted from the fertilizer tank (12L).

So 0.1 x 100 / 12 = 0.83 drops of ph down per liter is how much we should increase it by.

So 2 drops + 0.83 = 2.83 drops per liter, so for a 40 liter tank we would need 113 drops.

**However**, our fertilizer tank still has 28 liters of solution which contains 2 drops of ph down per liter.28 x 2 drops = 56 drops

So the total amount of drops needed to get to 113 drops would be 113 - 56 = 57 drops.

---------------------------------------------------------------------------------------------------------------------

Dunno if I explained this in a way that normal people can understand... but yeah, this should keep ppm and ph really steady and drastically reduce the amount of times you need to check on things.

I wrote this in kind of a rush so let me know if I made any mistakes or if the whole thing even makes sense lol

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