TDS: Is this really a critical water paramet

[solo]

My water is 3 months old, but the water chemistry actually seems really good right now and stable.  

ph is hanging at 7

TA is hanging about 120

Calcium hardness is in the low 200's

For close to last month the water has been in this range.  All I do is add a little dichlor when I get out and shock every other week or so (with dichlor).  I hate to empty the tub and lose this great chemistry.

But the TDS is at 1600 at last check and will probably soon be at 2000.  What impact does too high a TDS have on your water chemistry/system?

[Chas]

When I was servicing commercial pools and spas, the county inspector would shut us down - or sometimes just be nice enough to make me promise to fix it - if the TDS got too high. Of course, the only way to get that parameter down was to change all or part of the water.

Since you are using diclor, you should be able to go four months between water changes. Six in a pinch. At that point, I would say you are due to change regardless of the TDS.

So I guess I'm saying no, TDS is no biggy since I like to recommend water changes every four months.

HTH

 8-)

[wmccall]

To me, this says your doing a good job overall, but eventually, there is a cliff type event where despite all your good care you just can't keep it where it should and the water gets cloudy when you use the jets and gets cloudy faster between dichlor addition.

[Steve]

In my expereince, it is impossible to give people a "timeline" on water longevity unless you have a clear understanding on the source water, potential usage of the spa and its initial TDS reading.

If your TDS starts off at 150, sure you may get close to 6 months (which is pushing the envelope a bit IMO), but if your TDS is starting off at 800, you may only get 2-3 months (if that). We had many people on well water that had initial readings of 1000+ TDS that only got 4-6 weeks out of a fresh fill.

The best analogy for TDS is a coffee cup. You can keep adding sugar to it but at some point the coffee becomes saturated and the sugar will not dissolve and instead, sit in the bottom of the cup. Anything past 1500 TDS in a spa prevents your chemicals from properly doing their job as the water is now becoming saturated essencially throwing good money after bad.

The mistake many people make is that they base their water quality off of clarity. Battery acid is also clear...

[Chas]

That's a very good point about the fill water TDS Steve.

If your source water is high in TDS, then yes, you may want to use this to determine the water change interval. You should be able to take some tap water to a dealer and have it tested.

 8-)

[stuart]

TDS is one of the most overlooked problems in water chemistry. People often keep water in their spas for way to long and don't understand that "stressed" water will not maintain good levels.

Often you drift into adding more products to the water to balance it without realizing your doing it. With a busy schedule you may not even recall what you did last time, you just adjust for the moment your out there.

Every dealer should have a TDS meter to offer testing for their customer but most don't.

Wow! I just went back and read the people answering...Solo you got lucky on who picked up this topic, I wonder if that is significant of us "old-timers" being more concerned about TDS than most. 8-)

[Pathfinder]

TDS is the first thing I check in testing when dealing with a new customer or problem water. If the readings are too high no sense testing the rest.  Our city water is pretty good from the getgo  ph 7.0  alk 80 hardness 70 and TDS  usually between 70-90ppm

[TubsAndCues]

In my expereince, it is impossible to give people a "timeline" on water longevity unless you have a clear understanding on the source water, potential usage of the spa and its initial TDS reading.

If your TDS starts off at 150, sure you may get close to 6 months (which is pushing the envelope a bit IMO), but if your TDS is starting off at 800, you may only get 2-3 months (if that). We had many people on well water that had initial readings of 1000+ TDS that only got 4-6 weeks out of a fresh fill.

The best analogy for TDS is a coffee cup. You can keep adding sugar to it but at some point the coffee becomes saturated and the sugar will not dissolve and instead, sit in the bottom of the cup. Anything past 1500 TDS in a spa prevents your chemicals from properly doing their job as the water is now becoming saturated essencially throwing good money after bad.

The mistake many people make is that they base their water quality off of clarity. Battery acid is also clear...

Thank you, thank you, thank you!!!   I so often use almost this exact same analogy to explain this to my customers.  

And moreso, thank you for the battery acid comment!!!  Once again, I have the hardest time getting people to understand that just because your water is clear it doesn't mean it's not harmful to your tub.


And Solo, thank you for asking this question.  It's refreshing to see someone who is actively seeking out the information so they can keep their investment up to snuff.

[tony]

Acceptable TDS levels can be a confusing number.  ANSI/NSPI-4 1999 changed the standard to a maximum of 1500 ppm greater than pool/spa startup.  The NSPI guidelines show 300 pm minimum, 1000-2000 ppm ideal and 3000 ppm maximum with 1500 ppm maximum at pool/spa startup.  To get value from a TDS measurement, you need to know what the TDS level of your water is at a new fill.  Add 1500 ppm to that number to get to the level you should change your water.  3000 ppm is the absolute upper limit.

[Steve]

Acceptable TDS levels can be a confusing number.  ANSI/NSPI-4 1999 changed the standard to a maximum of 1500 ppm greater than pool/spa startup.  The NSPI guidelines show 300 pm minimum, 1000-2000 ppm ideal and 3000 ppm maximum with 1500 ppm maximum at pool/spa startup.  To get value from a TDS measurement, you need to know what the TDS level of your water is at a new fill.  Add 1500 ppm to that number to get to the level you should change your water.  3000 ppm is the absolute upper limit.

I haven't read this data but my opinion is that a spa and a pool are entirely different creatures when it comes to what is exceptable TDS readings and should not have similar data or requirements for suggested draining. The drastic difference in volume of water alone would be enough to suggest differing requirements of TDS IMO.

I have always suggested that 1500ppm is MAXIMUM for a spa and 2500-3000ppm for a pool but that's just what I was taught many years ago. I'm guessing water hasn't changed much over that period of time...

[yt]

Is there a TDS kit you can buy or do you have to take a H2O sample to your dealer to test?

[Vinny]

I haven't read this data but my opinion is that a spa and a pool are entirely different creatures when it comes to what is exceptable TDS readings and should not have similar data or requirements for suggested draining. The drastic difference in volume of water alone would be enough to suggest differing requirements of TDS IMO.

I have always suggested that 1500ppm is MAXIMUM for a spa and 2500-3000ppm for a pool but that's just what I was taught many years ago. I'm guessing water hasn't changed much over that period of time...

I have found this to be true on all the water parameters between pools and spas. I had a heck of a time getting my water to stay nice in the spa even though I had 4 years of water care under my belt. After about 6 months (yes, I'm dense) it dawned on my that I had to change the way I took care of my spa water.

TDS in a pool may not be as problematic for most people, winter has us dumping out the water in our pools. TDS shouldn't be problematic in our spas as long as we follow the dump and refill every 3-4 months. I guess guess using MPS may get your TDS higher during that time but as long as the water is managable you'll be a short time away from a refill.

Although I don't measure TDS there are definate signs of it - ozone bubbles getting really small is my indication I'm getting close to a water change. I'm at that point now since I had to fight that bacteria problem in my tub, I was planning on refilling in March - I may do it sooner if this weather stays the way it has.

[tony]

I have found this to be true on all the water parameters between pools and spas. I had a heck of a time getting my water to stay nice in the spa even though I had 4 years of water care under my belt. After about 6 months (yes, I'm dense) it dawned on my that I had to change the way I took care of my spa water.

TDS in a pool may not be as problematic for most people, winter has us dumping out the water in our pools. TDS shouldn't be problematic in our spas as long as we follow the dump and refill every 3-4 months. I guess guess using MPS may get your TDS higher during that time but as long as the water is managable you'll be a short time away from a refill.

Although I don't measure TDS there are definate signs of it - ozone bubbles getting really small is my indication I'm getting close to a water change. I'm at that point now since I had to fight that bacteria problem in my tub, I was planning on refilling in March - I may do it sooner if this weather stays the way it has.

I completely agree...a pool is a whole lot easier to maintain than a spa.  As Steve mentioned earlier, source water can make a lot of difference in water care, especially regarding TDS.  Most start up water issues can be adjusted but if your TDS starts high, you will most likely have a more difficult time with your water and may need water changes sooner than another might.  All water has some TDS or at least should have some TDS.  For instance, the calcium in your source water will be part of the makeup of your start up TDS.  This is why the standards state a minimum of 300 ppm TDS to start.  Ideal water gets changed at 1000 - 2000 ppm TDS.  If you start at 300, add 1500...at 1800 ppm you're in very good shape.  If your source water has 800 ppm TDS, to stay in the ideal range you should only add a maximum of 1200 ppm.  The worst acceptable source water, according to NSPI, would be 1500 ppm of which you could keep until TDS levels reach 3000 ppm....but this would be a worse case situation...but it may be a situation some people need to deal with.

[Shaamus]

Is there a TDS kit you can buy or do you have to take a H2O sample to your dealer to test?

AquaChek makes a TDS strip, but I don't know how effective they are.

[Steve]

I completely agree...a pool is a whole lot easier to maintain than a spa.  As Steve mentioned earlier, source water can make a lot of difference in water care, especially regarding TDS.  Most start up water issues can be adjusted but if your TDS starts high, you will most likely have a more difficult time with your water and may need water changes sooner than another might.  All water has some TDS or at least should have some TDS.  For instance, the calcium in your source water will be part of the makeup of your start up TDS.  This is why the standards state a minimum of 300 ppm TDS to start.  Ideal water gets changed at 1000 - 2000 ppm TDS.  If you start at 300, add 1500...at 1800 ppm you're in very good shape.  If your source water has 800 ppm TDS, to stay in the ideal range you should only add a maximum of 1200 ppm.  The worst acceptable source water, according to NSPI, would be 1500 ppm of which you could keep until TDS levels reach 3000 ppm....but this would be a worse case situation...but it may be a situation some people need to deal with.

Interesting post Tony and I've heard this before. I agree with the first part of your post but it's the last few sentences I question (understanding you are just quoting NSPI guidelines).

It confuses me and I haven't had someone explain this theory to me clearly...
If water is water and TDS is TDS and we understand that water becomes saturated at a certain ppm (1500 -2000ppm) why are we just adding 1500ppm to the source water reading to come up with a refrence point of draining (ie 3000ppm)?

Water doesn't care what its initial reading was when it reaches a point of saturation does it? :-?