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Sulfur In Water, How To Get It Out?


steinbej
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Hi folks,

I just moved into a house with a small indoor pool. The water is well-water, which is good in every way except for a high sulfur content. So I got a Culligan oxidizer/filter system which has made the household tap water perfect.

BUT, the pool was obviously filled many many years ago with tap water from the well. The pool water is still quite sulfur-smelling. I talked to my local pool supply/support company about draining it and refilling it, but they advise against doing so because of the risk of water seeping in from the ground behind the liner while the pool is relatively empty during draining and refilling process. So that leaves me with a pool full of sulfur-y water. Pool supply folks have no further ideas about how to get the sulfur out.

Any ideas here? Perhaps some sort of float equipped with an absorptive chemical or perhaps with a catalyst? Or just a special filter or something?

-- Josh

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Reverse Osmosis (RO) could clean the water removing everything in it (including sulfur) while not changing the water level, but it's not cheap and not available in all areas. There's Clean Water Products in Arizona and Pool Services Technologies, Inc. in southern California, but you'd have to see if there is anyone doing this in your area.

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Any sulfur in the water that would cause a "sulfur smell" would be in the form of H2S (hydrogen sulfide), which is in equilibrium with the hydrogen sulfide anion HS-

(pKa H2S = 7.00). Any hydrogen sulfide should have been oxidized to sulfur or sulfate if the pool has been treated with chlorine.

HS- + OCl- --> S + Cl- + OH-

HS- + 4 OCl- --> SO42- + 4Cl-

Any elemental sulfur should be filtered out. The sulfur would be best filtered by a DE filter, although you might need to use an activated carbon filter to remove final suspended sulfur.

Sulfates shouldn't cause any smell. Shock to about 10 ppm using liquid chlorine (sodium hypochlorite) and keep it there until all of the sulfide has been oxidized.

Hydrogen peroxide can also be used to oxidize the sulfide to sulfur or sulfate if the chlorine does not work. Hydrogen peroxide is a chlorine reducer so you would have to use enough to reduce all of the chlorine and then add about 3 ppm hydrogen peroxide for every 1 ppm sulfide. pH needs to be raised to about 8.2 for this to be most effective.

A properly designed, installed and operated ozone system can give very good water quality. However, a well designed system is expensive for the initial setup.

Reference

Use of MPS (aka non-chlorine shock) to shock might help oxidize sulfides to either sulfur or to sulfate.

Have you had the water tested for hydrogen sulfide? What are all of your other chemical readings?

Free chlorine

Combined chlorine

pH

Total alkalinity

Calcium

Cyanuric acid

Temperature

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Our florida home has well water that REALLY stinks from sulpher, every trip to florida (apx every 3 months) we have to top off the pool with about 6 inches of this nice well water (we have a leak) I shock the pool with chlorine and MPS. The smell is gone the next day. I also clean the filters out after a couple of days

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Shocking and filtration should resolve the sulfur issue.

Note: Some pools use an alternative sanitizer called Baquacil. If the previous owners used Baquacil, then you cannot shock with chlorine or MPS (unless you decide to do a full conversion).

You should ask the previous owners if they ever used Baquacil. If the previous owners are not available, you could have the water tested for Baquacil at the local pool store. Also, what chemicals did the previous owners leave for you? Did they leave any test kits?

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  • 4 weeks later...

Shocking and filtration should resolve the sulfur issue.

Note: Some pools use an alternative sanitizer called Baquacil. If the previous owners used Baquacil, then you cannot shock with chlorine or MPS (unless you decide to do a full conversion).

You should ask the previous owners if they ever used Baquacil. If the previous owners are not available, you could have the water tested for Baquacil at the local pool store. Also, what chemicals did the previous owners leave for you? Did they leave any test kits?

I don’t know about the advice that you can never drain the pool, not positive on your location in the country, however, people drain their pools all the time to clean/paint/repair. You do want to make sure your water table is low when you drain a pool, you do not want to drain it when there is a lot of hydrostatic pressure, so wait until it has been dry and no snow melt. You also want to fill it back up right away after draining. So my advice to get rid of the sulphur smell is to drain and re-fill with your Culligan filter (if that kind of volume will go through it relatively quickly (or) have water trucked in.

As far as heat pump..... Heat pumps will heat the pool/spa water just fine, however, like you said not as quickly as a gas heater. Another fact about heat pumps is the colder the outside air is, the less efficient the heat pump becomes. I've heard positive things about this hayward heat pump if you do go that route.

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steinbej,

Often, the "sulfur" or "rotten egg" smell from well water is the result of a harmless bacteria that can exist and thrive at certain temps.

As others have said, shocking the pool with chlorine (if it is a chlorine pool) will very likely eliminate it.

Shocking an indoor pool is a little more problematic than outdoors. Posting the set of test results requested by quantum will be really helpful.

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Hi folks,

Great that so many are being helpful with suggestions. Also nice that they are all the same suggestion (shocking w chlorine), which keeps a novice like me from having to wonder about which suggestion is the right one.

However, if all these really elementary suggestions to shock are correct, why can't my local pool company in business almost 50 years offer me the same solution? That's what worries me. I don't know how smart they are, but I figure they've faced by now nearly every conceivable problem in pool management and maintenance, yet they had no answer for me on this issue.

Of course, I shouldn't ask you folks why they don't know this, I guess I'll have to ask them.

Thanks again for all the great generous suggestions.

Best,

-- Josh

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