Question about TDS - RO Filter

[dr exum]

Recently got a TDS meter,

oh my.... three big tanks are 1200 / 800 / 800 -

tested a little 75g and they are 130...

turned my RO, have a cheapie, makes only 50 gpd - (gallons per day) - its running into my 625g (750g w/sump)

will this take a month to dillute or what? have a 150g stock tank, considering filling that and pumping water in during w/c fill up if this will not work

i understand it will work eventually, this is the math question,

pumping 50 gallons per day into 750 g tank with TDS 1200 - how long we thinking

ty

 

[jjohnwm]

You can't calculate how long it will take without knowing what's causing those high numbers in the first place. If that factor is still affecting the tank, you'd need to know how fast it is raising the TDS while you are trying to lower it by dilution.

 

[dr exum]

need to read more about the TDS, my tap is 30 it seems,

i had drip system / auto w/c and nitrate reactors running for years in there with big fish

its not been stocked for at least 2 years
now its got a dozen 3" fish and 2 pleco in there, nitrate reactor and pumps turned all the way down,

 

[dr exum]

guess the question i have now is whats the difference between adding tap water (30 tds) vs my RO water (0 tds)

my water is hard AF in that tank too from the nirtrate reactor,

gonna get junk outta sumps...

 

[M1A1]

You can't calculate how long it will take without knowing what's causing those high numbers in the first place. If that factor is still affecting the tank, you'd need to know how fast it is raising the TDS while you are trying to lower it by dilution.

This is 100% accurate as we can't calculate exactly how long it will take with what you've stated but we can make some assumptions to get an idea of how long it will take. Assuming there's nothing increasing the TDS in the tank and that your drip system perfectly removes only high TDS water and replaces it with 0 TDS water then it would take 12 days to get to 600, 21 days to get to 300, and 30+ days to get to 150. Neither of these are good assumptions by the way.

If you just do big 150 gallon water changes (WC) on the 750 gallon system then one WC gets you to 960, two WC is 768, three is 615, four is 492, etc. Multiply the starting TDS by 0.8 (because (750-150)/750 = 0.8) to estimate the TDS after the WC.

Using tap water that has >0 TDS is more complicated to calculate but since you're starting at 1200 then the results should be about the same as the 0 TDS RO water replacement until the tank gets to much lower TDS. Like it'll take longer to reduce the TDS once the tank TDS is at 150 but that's pretty low to start with.

 

[dr exum]

i

This is 100% accurate as we can't calculate exactly how long it will take with what you've stated but we can make some assumptions to get an idea of how long it will take. Assuming there's nothing increasing the TDS in the tank and that your drip system perfectly removes only high TDS water and replaces it with 0 TDS water then it would take 12 days to get to 600, 21 days to get to 300, and 30+ days to get to 150. Neither of these are good assumptions by the way.

If you just do big 150 gallon water changes (WC) on the 750 gallon system then one WC gets you to 960, two WC is 768, three is 615, four is 492, etc. Multiply the starting TDS by 0.8 (because (750-150)/750 = 0.8) to estimate the TDS after the WC.

Using tap water that has >0 TDS is more complicated to calculate but since you're starting at 1200 then the results should be about the same as the 0 TDS RO water replacement until the tank gets to much lower TDS. Like it'll take longer to reduce the TDS once the tank TDS is at 150 but that's pretty low to start with.

i was always cautious to change water when nitrates were 5ppm or below, did not want to disrupt tank cycle or this is not accurate?

i took 200 gallons out two days ago and 200g out today

it was at 1600 before i did w/c today,
will turning up my filter help?

i turned it down as nitrate was not measurable

 

[duanes]

A lack of nitrate does not disrupt the tanks cycle, the sessile bacteria "needed" in the cycle consume ammonia and nitrite, their waste product is nitrate.