Question for the Water Experts

[Bucketeer]

I have a question regarding the corrosiveness of the reject water coming out of my R/O unit. The prefiltered water (1655 uS) is softened using Sodium Chloride, then it's run through the R/O unit and discharged into the laundry tub in the basement. The reject water is 1815 uS which is only 160 uS more than the prefiltered water, but is the constant flow of salt-rich water going to eventually corrode my iron/steel sewer line?

Incidentally the pre-softened water is 1328 uS. Or, as some might say.....close to liquid rock. The R/O water is 34 uS :) Soft enough for me.

Thanks,

Bill

[LizStreithorst]

Here I go opening my mouth without being sure of the answer. jBut this thread needed to be bunped back up, anyway.

I always thought that it was RO water that is corrosive. Since it has virtually no mineral content, it drawn minerals from your pipes to it. That is corrosion, or rust.

Water with a high mineral content on the other hand will leave deposits or give up minerals to the pipes.

Please someone correct me if I'm wrong.

[dishpanhands]

I don't think the TDS will tell you how corrosive the water is..Its the PH that tells that..

[Bucketeer]

Here I go opening my mouth without being sure of the answer. jBut this thread needed to be bunped back up, anyway.

I always thought that it was RO water that is corrosive. Since it has virtually no mineral content, it drawn minerals from your pipes to it. That is corrosion, or rust.

Water with a high mineral content on the other hand will leave deposits or give up minerals to the pipes.

Please someone correct me if I'm wrong.

Don't be worried about not being sure of the answer, that's
why I asked the question ;)

[Bucketeer]

I don't think the TDS will tell you how corrosive the water is..Its the PH that tells that..

I'll check the pH and get back to you.

Bill

[Bucketeer]

Just checked the pH. It's between 7.5-8.0.

Is that alkaline enough to cause corrosion? Wouldn't think so, but what do I know! ;)

Thanks,

Bill

[korbi_doc]

Just checked the pH. It's between 7.5-8.0.

Is that alkaline enough to cause corrosion? Wouldn't think so, but what do I know! ;)

Thanks,

Bill

:D I'd have killed for water like that in NJ...that is not corrosive....try a ph of 2.0 or 3.0, the copper water pipes were old in the house & you would've been appalled by the look of the pipe walls....paper thinnnnnnnn.....that is corrosive, that's why I had so many sudden floods in the basement, pipes would just pop!!!! The water softener had a cylinder for acid buffer that didn't do much good, lol...anyway, now my water is much better here in Tn, very soft, except that it has too high a ph, 8.2 or so...tough to keep down...just another challenge, lol, Dottie ;)

[Bucketeer]

I'd have killed for water like that in NJ...that is not corrosive....try a ph of 2.0 or 3.0, the copper water pipes were old in the house & you would've been appalled by the look of the pipe walls....paper thinnnnnnnn.....that is corrosive, that's why I had so many sudden floods in the basement, pipes would just pop!!!! The water softener had a cylinder for acid buffer that didn't do much good, lol...anyway, now my water is much better here in Tn, very soft, except that it has too high a ph, 8.2 or so...tough to keep down...just another challenge, lol, Dottie

Wow Dottie, pretty strong acid back in NJ. Good thing for the fish and your bank account you moved!

Bill

[discussmith]

The water that comes out of your softner is not salt water. The salt is the source of sodium ions that the softner resin needs to use to replace the carbonate ions that cause your water to be hard. So instead of carbonate laden water which causes lime scale and the inability for surfactants (soap) to work as well, you have sodium laden water.

[annieb]

The water that comes out of your softner is not salt water. The salt is the source of sodium ions that the softner resin needs to use to replace the carbonate ions that cause your water to be hard. So instead of carbonate laden water which causes lime scale and the inability for surfactants (soap) to work as well, you have sodium laden water.
I don't think an R.O system will remove sodium chloride from the water.Your meter is giving you PPM or uS TDS based on calcium, Magnesium, and some trace minerals in the water. Your water might give you a TDS reading of 35uS after flowing through the R.O unit and the water might contain 900 mg of sodium chloride per 8 ounces of water. Something to think about.

[dishpanhands]

Just checked the pH. It's between 7.5-8.0.

Is that alkaline enough to cause corrosion? Wouldn't think so, but what do I know! ;)

I was saying that an RO makes the TDS go up and doesn't change the PH of the waste. Its about the sames PH as the water going in, so it won't be more corrosive then your tap water will be...now for the product water the PH of it can change a great amount in a short time..

[Bucketeer]

The water that comes out of your softner is not salt water. The salt is the source of sodium ions that the softner resin needs to use to replace the carbonate ions that cause your water to be hard. So instead of carbonate laden water which causes lime scale and the inability for surfactants (soap) to work as well, you have sodium laden water.

Got it! Makes sense the Cl-- ions are attached to the positively charged Ca++ ions..right? I think I'm beginning to recall some of that general chemistry stuff now.


I was saying that an RO makes the TDS go up and doesn't change the PH of the waste. Its about the sames PH as the water going in, so it won't be more corrosive then your tap water will be...now for the product water the PH of it can change a great amount in a short time..

Yep, R/O water doesn't have the buffering capacity. Thus the need for R/O Right.

Thanks,

Bill

[Buckeye Field Supply]

What folks are thinking of is DI water.

DI water is very aggressive - so you'll never see it used with metal fittings, pipes, etc.

Your RO waste water is a non-issue.

On another note, you mentioned that your waste water is constantly flowing. Really? It shouldn't be.

Russ @ BFS

[Bucketeer]

On another note, you mentioned that your waste water is constantly flowing. Really? It shouldn't be.

I think it flows constantly because I'm constantly tapping off the pressure tank :shocked2: Otherwise it's not working correctly......can't say that yet.

Once I get a booster pump it should be able to keep up with my needs and then the auto shut-off valve will be put to work.

Bill