RDWC top-off water question

[ColonelBlake]

This is a silly question, but here it goes.

I'm running a RDWC system with a reservoir ( 29 gallon tote ). This res feeds multiple 5 gallon buckets via a submersible pump which are in turn brought back to the res via gravity. Within this res I have a float switch that's plumbed to a 50 gallon drum filled with ph'd RO water. This keeps the water level correct so the pump doesn't burn out and compensates for water consumed by plants. I'd estimate that ~5 gallons of water is pulled from this drum daily.

So my question is, should this 50 gallon drum contain nutes or should it be just plain water? I have a separate 50 gallon drum for res changes.

Thank you in advance!

 

[Old Salt]

@West Hippie grows in DWC or RDWC.

My take on the problem is at a res change:
turn off the water from the drum, and fill it with pH'd water
after a day
- measure the TDS (PPM) of the reservoir
- measure the water needed to fill the reservoir
- compute the amount of nutrients needed
- bring the drum to 90% of that value
- turn on the water from the drum

This will give you some leeway for correction.

As an example, assume you have 4 buckets with 3 gallons in each, and 20 gallons in the reservoir, so 32 gallons in that part of your system. Let's say your TDS is 850 PPM.

After a day, your plants have consumed 4.5 gallons, and the TDS drops to 750 PPM.

Now you have 27.5 gallons in the system at 750 PPM, to bring it back to spec, you need 4.5 gallons of water and we need to determine the TDS, so

32gal * 850 PPM = 27.5 gal * 750 PPM + 4.5 gal * X
27200 gal PPM = 20625 gal PPM + 4.5 gal * X
6575 gal PPM = 4.5 gal * X
1461 PPM = X

90% of that is 1315 PPM, add nutrients to your drum to reach this level. You'll need to add a more concentrated nutrient solution to your reservoir every two to three days to bring it to your exact level.

This will work, but West Hippie may have a better method.

 

[West Hippie]

Mine is a 20 gallon reservoir, flood and drain. In flower . I change the reservoir every 7 days and would love to have 50 gallons of ro water ready to go . I top mine off to , but I want to put it in myself so I and everybody knows what went in there !
Five gallons a day wow you must have at least 20 going ?

 

[ColonelBlake]

Thanks for your reply gents!

Yes, I have more than that amount. The system is 100-120 gallons in total.

Ty for the formula above! I'm a bit high atm so I didn't completely comprehend it. But tomorrow it will sink it.

Thanks again to both of u and have a good night!

 

[ColonelBlake]

@Old Salt : The 50 gallon drum in question is just for top-off water ( ph'd ro water only ). It simply replenishes water that is consumed by the plants. Which is several gallons a day. I have another 50 gallon drum for res changes ( this contains ro water w/ calmag + MC at a specified ppm and ph ).

I think for now I'll just keep the top-off water plain RO and add MC to up the ppm as needed. But I'm not sure if this is the correct way to go with MC. Seems like it would be ok though. On most days I've been adding ~25g of MC per day to maintain a 800-850 ppm level. When I do res changes ( using other drum ), I'm now adding 6g/gal of MC + 1ml/gal of calmag. Res changes are done weekly. Top-off water is constantly being dripped into the res via float valve ( see images ).

 

[Old Salt]

It looks like you have it under control. Do you manually mix the Mega Crop in the reservoir, or do you have another method?

 

[ColonelBlake]

For daily top offs I mix 25g in a 2 quart pitcher with a quart of water, stir it with a wine making spoon for a minute or so (another hobby), and then put it in the res.

For awhile I was using a stirring mechanism ( wine degasser ) on a cordless drill. But it seemed like an overkill.

 

[Old Salt]

That works. I drop an aquarium wave generator into my 5 gal mixing bucket for half an hour. I'm just lazy, and work hard keeping it that way.

 

[ColonelBlake]

That's a smart idea!

 

[Old Salt]

I can't take credit for this. West Hippie introduced me to the idea.

 

[No Pain]

This is a silly question, but here it goes.

I'm running a RDWC system with a reservoir ( 29 gallon tote ). This res feeds multiple 5 gallon buckets via a submersible pump which are in turn brought back to the res via gravity. Within this res I have a float switch that's plumbed to a 50 gallon drum filled with ph'd RO water. This keeps the water level correct so the pump doesn't burn out and compensates for water consumed by plants. I'd estimate that ~5 gallons of water is pulled from this drum daily.

So my question is, should this 50 gallon drum contain nutes or should it be just plain water? I have a separate 50 gallon drum for res changes.

Thank you in advance!

You got some great advise from @Old Salt and @West Hippie

I run a rdwc system (current culture ) I run 6 grow modules 50 gallons circulating in the system and a 50 gallon auto top off bucket with a pump that recirculates the solution through its own chiller . At peak my ladies have been known to take up 5-7 gallons a day it is truly amazing to see . So I run a nutrient solution in my top off ..before I would suggest that I would suggest adding something like a Blue lab guardian to watch levels in the system , that way you know what's being taken up ..is it more water than nutrients , vise versa ..that tool easily aids you in the direction you need to go . You could measure it manually but I like to be able just to walk in the room and look at the meter .

also I use the top off tank for res changes , the day before im going to do a res change and its done every seven I fill the top off up mix the nutes and turn the valve to the system off and turn that chiller down to the same temp as my system , it makes for quick changes that does not shock the roots of the plants with large temp changes .

P.s depending on growth phase and drift i run the top off at a slightly different ph to aid in keeping it stable .

 

[ColonelBlake]

You got some great advise from @Old Salt and @West Hippie

I run a rdwc system (current culture ) I run 6 grow modules 50 gallons circulating in the system and a 50 gallon auto top off bucket with a pump that recirculates the solution through its own chiller . At peak my ladies have been known to take up 5-7 gallons a day it is truly amazing to see . So I run a nutrient solution in my top off ..before I would suggest that I would suggest adding something like a Blue lab guardian to watch levels in the system , that way you know what's being taken up ..is it more water than nutrients , vise versa ..that tool easily aids you in the direction you need to go . You could measure it manually but I like to be able just to walk in the room and look at the meter .

also I use the top off tank for res changes , the day before im going to do a res change and its done every seven I fill the top off up mix the nutes and turn the valve to the system off and turn that chiller down to the same temp as my system , it makes for quick changes that does not shock the roots of the plants with large temp changes .

P.s depending on growth phase and drift i run the top off at a slightly different ph to aid in keeping it stable .

Great advice! Thank you for your input!

 

[No Pain]

Great advice! Thank you for your input!

You are very welcome .

 

[West Hippie]

That's a smart idea!

I can't take credit for this. West Hippie introduced me to the idea.

I can’t take credit for it , it was the MC talking . It made me lazy not mixing 7 to 9 nutrients into the reservoir. And the clean up is the easiest I’ve ever had!