Rheem/Raypak, TDS, and Maintenance

[crustfan]

I have a salt water pool and a new Rheem P-M206a. The manual recommends:
Salt - 4500ppm Max
Total Dissolved Solids - 3000ppm Max **

Underneath the table the ** is explained as:
**In salt water chlorinated pools, the total TDS can be high a 6000ppm.

Does this mean 6000ppm is the TDS max for a salt water pool or is it a warning for swg pool owners and 3000 is still the max? The second option doesn't make sense to me since 3000 is a normal salt level and they even state 4500 max for salt.

The manual advises:
"If the mineral content and dissolved solids in the water become too high, scale forms inside the heat exchanger tubes, reducing heater efficiency and damaging the heater."

I had my chemistry tested at the store the other day and TDS was 4000ppm, outside their range of 300-3000ppm.

My salt was 2700ppm. What does this mean? Does my reading mean 4000 total = 2700 salt + 1300 other things (my guess)? Or 2700 salt + 4000 other = 6700? I would guess that my TDS & salt is within Rheem requirements ie less than 6000 and less than 4500.

I've read on here not to worry about TDS. I checked a Pentair and a Hayward manual and they don't mention TDS. What's the real story?

In addition to water chemistry, the manual recommends periodically checking flame (easy visual inspection), checking the voltage on the water pressure switch, cleaning burners, and tube cleaning. Anyone do these themselves or best to have it done annually by a serviceman?

I dismantled the old corroded Raypack 2100 millivolt heater so I can bring it to the junk yard and learned alot in the process about how they are built. It seems pretty much to be the same design except for the digital control and electronic ignition. Are there any parts worth salvaging?

http://www.rheem.com/documents/digital-and-millivolt-pool-spa-heaters-duplicate

 

[JasonLion]

Salt counts towards TDS, so TDS of 4000 and salt of 2700 means 1300 of other things. Their recommended TDS limit is 6000 with a salt pool, so you are just fine.

TDS is the total of all dissolved solids. In reality it very much matters which particular solids are in the water. It is perfectly possible for TDS to be very very high and everything just fine, and it is equally possible to have TDS quite low and still be in big trouble. Rheem seems to have decided to write it down in approximate terms using TDS as a proxy for other levels, but TDS isn't the number that matters. The real risks are from salt at 6000+ or CSI at 1.0+. (Best to stay well below those numbers to give yourself some room for measurement errors, etc, thus their 4500 salt limit.) In any case, those are more complex numbers that not everyone understands, so it seems they have decided to simply things to something more people have a better chance of understanding, even if it loses some technical accuracy in the process.

 

[ps0303]

I do not know of anyone that does any regular maintenance on a gas pool heater. Either it works or it doesn't. It's not like an AC unit that you should clean and perform regular preventive maintenance on.

 

[crustfan]

Thanks.

I got the following response from Rheem/Raypak. btw, Pool School recommends a 24hrs pump run when adding salt; below it suggests 48 hours. I also guess that he means the "typical" run time is 8 hours on, *16* hours off otherwise the time of day would change with 8 on / 8 off. I've read that you want to make sure the pump runs during the day.




From Raypak:
Pool chemicals of all types need to be reviewed daily during the warmer months to ensure they maintain the levels necessary for sanitation and protection of the various components of your pool system.

With the popularity of "salt systems" all manufacturers had to readdress their chemical requirements as it relates to warranty and failures. The main concern has been the need to add salt and the failure to "totally dissolve" the salt before turning off the circulation pump. When a pool is controlled by a remote or a time clock, homeowner must reset these controls to allow for continuous running for at least 48 hours rather than the typical on 8 hours and off 8 hours.

Normal chlorines sanitation used chemicals that would "lower" the Ph of the pool water which would cause failures with copper or cupro nickel tubes as well as anything else within the system that was metal or copper. Now with salt it is just the opposite of Ph ranges as salt raises the Ph and will cause the same problem. Salt also raises TDS - total dissolved solids- which is basically the "health" of the water. When TDS rises above allowable limits there is not an additive that will adjust this...you have to drain the pool and refill. Outdoor pools did not suffer nearly as much from TDS before salt due to the constant evaporation of the water and the automatic refill of lost water sometimes as much as 2 inches a day.

Raypak raised the allowable TDS to accommodate the new salt santitation usage but you have to check the TDS level far more frequently than with just chlorine.

Cupro nickel is not a "cure" for salt, it is just a different blend of copper and nickel but will eventually fail just as basic copper, so you did not make a mistake, in fact, if you pay attention to your pool chemistry, you actually saved money by buying the standard copper waterway.

Warranties do conflict with heaters and recommendations by salt manufacturers so this is an ongoing problem. What is all comes down to is maintaining your Ph levels based on the type of pool you have and this is normally the usage of "stabilizer" and also understanding the movements caused by your other pool chemicals.

I would suggest visiting a national pool retailer and taking a water sample with you so they can see firsthand what you are facing.

Dave


-----Original Message-----

I just replaced a corroded Raypak heater after 8 yrs service with a Rheem 206a. The unit that was installed has a standard copper heat exchanger and I am very worried about maintaining the proper water chemistry given that I have a salt water pool. My installer did not tell me about the cupro-nickel option and I wonder if that is a mistake. Is it possible to keep this new heater corrosion free? I am confused by the guidelines on the first page of the instructions. Currently my salt is 2700ppm (Hayward recommends 2700-3400) and TDS 4000. I'm confused by TDS. What is meant by maximum allowable salt level is 4500ppm but maximum TDS is 3000ppm. Doesn't TDS include salt, so how can the max TDS be less than the max salt or is this number of dissolved solids in addition to salt ie 4500 + 3000? Also there's mention of a 6000ppm number for salt below the chart. Does this mean that the max allowed level of salt for salt water pools is 6000ppm. Plus another 3000 for TDS?

 

[JasonLion]

Curious, they are spot on for some of the things they say, and way off for others. As they mention, PH is by far the most important thing. Low PH can damage the heater fairly quickly. On the other hand their discussion of TDS and outdoor pools is just dead wrong. TDS is higher in outdoor pools. Evaporation removes only water, leaving the dissolved solids behind. Adding more fill water brings in more dissolved solids, so the TDS level slowly goes up. TDS tends to go up in indoor pools as well, just not as much. Not that that makes much of any difference, as TDS really doesn't matter and certainly does not indicate "the "health" of the water."