Water Quality question

[AdamD]

Ok, so I've been growing for a decade, but just got my first TDS and pH meter last week. Testing the water out of my tap, I got a reading of almost 350 ppm with a pH of around 6.9. Testing the water out of my RO system I've had readings of between 100-120, which is better than the tap by a long shot, but still not where I expected it to be. I realize an RO system can only do so much with what it's given. The filters were changed in January. The pH of the water out of the RO system is also around 6.8, 6.9.

I guess my question is, should I send off for a water analysis? Should I expect more from my RO water? The system itself has only been in operation for about a year. Any comments or suggestions are appreciated.

 

[gonewild]

350ppm tap water is not so bad. Is it city water or from your own well?
120ppm from the RO is not so good.
Have you verified the accuracy of your new meter with a test solution?

 

[AdamD]

Yea I calibrated it. It is city water. I live in MO, lots of limestone, so I'm hoping most of the mineral content is Ca. But many of my friends are on wells, and they say the iron content is incredible. Also sulfur is a local problem as well.

 

[gonewild]

Yea I calibrated it. It is city water. I live in MO, lots of limestone, so I'm hoping most of the mineral content is Ca. But many of my friends are on wells, and they say the iron content is incredible. Also sulfur is a local problem as well.

Ask the city for a copy of the water analysis, no sense spending money on a test yourself. Do you see iron stains on your plumbing fixtures?

 

[AdamD]

No, mostly just calcium deposits. Every once in a while though the water will run a murky red in the bath for a day or two.

Would it be worth it to send off a sample of the RO water with fertilizer added for analysis? Has anyone ever done this? Just to get a sense of where your levels are at?

 

[gonewild]

It would be interesting and useful to know the content of the output from the RO unit. But dont add fertilizer to it for the test.
If you know the exact content of the water you start with it is easy to calculate the final content of the RO+fertilizer by using math.
But first make sure your RO unit is working properly or the water analysis will be of no use if you change the unit.

 

[tomkalina]

Output from your R/O system should be somewhere around 10-20 ppm TDS if your meter is correctly calibrated. If it's much more than this, somethings wrong.

 

[John M]

Output from your R/O system should be somewhere around 10-20 ppm TDS if your meter is correctly calibrated. If it's much more than this, somethings wrong.

Agreed.

 

[NYEric]

Output from your R/O system should be somewhere around 10-20 ppm TDS if your meter is correctly calibrated. If it's much more than this, somethings wrong.

Yep.

 

[Justin]

agree--R/O should put out 10-20 so there is something wrong with either the measurement or the R/O system. you can calibrate the pen with distilled water which should be approx 0.

 

[Ray]

Adam, when did you last changed the membrane? The filters are there to protect the membrane, but that should be changed periodically, as well. For example, since 2008, I have replaced mine 3 times.

 

[AdamD]

I haven't replaced the membrane, but that might be my next step. It's only been in operation for a year and a half, I planned on changing it in January. I think I'll change all filters and the membrane and report back. Knowing myself it will probably be a few weeks lol...

 

[gonewild]

In a year and a half how many gallons of water passed through the membrane?
Volume of water processed is more critical than the amount of time.

 

[AdamD]

True. I use at least 2.5+ gallons a day out of it on average. I fill up a gallon water jug for work (yes, I drink a gallon at work). Then I use on average a gallon a day for plants (sometimes less, sometimes more). Then I'd say at least another half gallon for drinking water for the household.

 

[AdamD]

Comes up to about 1,400 gallons. You could probably even round it up to 15. When ctsms are in full swing I can use a gallon a day on just them.

 

[gonewild]

You should get 3 or 4 times that amount of a membrane so something is probably not correct.
Or maybe the filter combo is set to remove only a part of the tds as a water conservation theme?
It's completely possible that the minerals that remain in your RO water are an asset to your plant nutrition.

 

[Ray]

Typical residential membranes are good for about 20,000 gallons.

Adam, if this is the system you purchased from me in 2008, I suspect that the lack-of-use over the 5 years you didn't use it led to membrane degradation.

New (dry) membranes are treated with a preservative and sealed in a theoretically air-tight bag to prevent bacterial degradation. Once that bag is opened, they need to be put into use immediately and the membrane housing kept full of water, as that prevents the bacterial attack.

 

[gonewild]

New (dry) membranes are treated with a preservative and sealed in a theoretically air-tight bag to prevent bacterial degradation. Once that bag is opened, they need to be put into use immediately and the membrane housing kept full of water, as that prevents the bacterial attack.

Ray, if the membrane is degraded and not working correctly what minerals are in the water? Will there just be a reduced equal amount of the minerals or will the membrane remove some minerals and leave others?

 

[AdamD]

Yes Ray it took me a while to install it lol... I bought it, moved, moved again, lost my collection, rebuilt, moved, moved again, and put it in last year. If the membrane is bad, should I replace the overworked filters as well? Also curious to know which minerals would sneak in.

 

[gonewild]

Adam did the membrane remain wrapped and sealed when it was not isn use? or did it come installed in the unit already?