Salt water pool - effect on concrete surround

[Kevandra]

Hello,

What a fantastic and informative forum. We made the big decision to have a pool installed in our backyard. The big dig is planned for the first week of October and we are first time pool owners. I've been reading as much as I can over the last few weeks. I have one question/concern I would like to post: Will a salt water pool limit the life of the concrete surrounding the pool? Is it any harder on the concrete than chlorine is?

The pool company is going to enlarge the concrete surrounding the pool (more than the standard three feet) to accommodate a path to our shed and a sitting area at one end. I read a couple of frightening articles about salt water affecting patio furniture and brick close to the pool. This approach will save us a bundle in landscaping with traditional interlock. I would like to ensure this is a good and cost effective idea that I won't regret down the line.

Any information or advice you can provide is appreciated. Thanks.

Kevin

 

[chem geek]

Welcome to TFP!

Salt splash-out is more of an issue with softer stone than for concrete, but it also depends on the amount of salt build-up and that depends on how much you splash-out how frequently, whether you get summer rains that would dilute or remove the salt, and how hot and dry the air is since that determines the rate of evaporation. It is the cumulative splash-out with evaporation that builds-up the salt. If it gets into softer stone or into concrete crevices, then the evaporation can recrystallize the salt putting pressure on the surrounding material. This is worst with magnesium sulfate, but it's still a problem with sodium chloride, only less so. Most people don't have any problem with their saltwater chlorine generator (SWG) and surrounding hardscape. Most problems seem to be in certain areas of the country like drier parts of Texas where some particularly soft local stone hardscape materials are used and where the weather is hot and dry in the summer. There are some issues reported in places like Arizona, but less so in places like Florida where there can be frequent summer rains or in the Northeast where there is also either rain or humid air.

If you are concerned about your concrete, you can seal it. That's probably a good idea to do anyway, especially if it's textured, and even if you don't have an SWG pool. For our hand-troweled concrete shown here we seal it every year with Glaze 'N Seal Multi-Purpose Sealer and also seal the plain coping as well.

 

[toofast]

I know this is an old thread, and I was 99% leaning toward a SWCG for my in-ground fiberglass new pool. Talked to my pool guy this AM, (who is also a concrete guy) and he was crazy against salt water around a stamped concrete patio. He claims that over time (10 plus years) the concrete will start to pit and eventually bad things will happen. Only way to avoid is to constantly wash down with fresh water, etc.

In all my research I just can't find a ton of pool owners that have this problem...of course if you look at our streets it is very evident, but we all know the levels are so much different. Figured I would add on to this thread as it was the only one I could really find.

Guess I am hoping to find some long term story's good or bad of stamped concrete and salt pool ? Any feedback is appreciated.

 

[mrshanes]

I know this is an old thread, and I was 99% leaning toward a SWCG for my in-ground fiberglass new pool. Talked to my pool guy this AM, (who is also a concrete guy) and he was crazy against salt water around a stamped concrete patio. He claims that over time (10 plus years) the concrete will start to pit and eventually bad things will happen. Only way to avoid is to constantly wash down with fresh water, etc.

In all my research I just can't find a ton of pool owners that have this problem...of course if you look at our streets it is very evident, but we all know the levels are so much different. Figured I would add on to this thread as it was the only one I could really find.

Guess I am hoping to find some long term story's good or bad of stamped concrete and salt pool ? Any feedback is appreciated.

I don't think salt alone damages concrete. What typically happens, especially in northern locales where salt is used to melt snow and ice is that it increases freeze/thaw cycles as the temperatures fluctuate. That's why roads, driveways, sidewalks, etc.. are damaged from using salt. Throwing salt on the concrete in the summer doesn't damage it. It may kill plants/shrubs next to it from runoff though. It certainly can also rust any patio furniture sitting nearby. My problem is the salt build-up on the railings, etc... over the season. It really calcifies on that stuff and is a pain to clean in the fall when I remove them.

 

[toofast]

Mmm....so this is where I struggle. In the NORTH we get hard freezes all winter. Below is what my buddy (who owns a concrete company shared with me)

Believe it or not, while concrete appears to be a very dense material, it is in fact quite like a blotter. It can and does absorb water. You can actually see this happen on a hot summer day. Sprinkle some water on your sidewalk or driveway and look very closely. You can actually see the water penetrate the surface of the concrete.

When you spread salt on your concrete to melt snow and ice, or if saltwater in spread in concrete, the salt dissolves the snow and makes a salt water mush or you have just pure salt water. The melting action of the salt allows water to enter the concrete. If the temperature then drops and the water freezes, the growing ice crystals can blast apart the concrete.

Salt is also hygroscopic. It attracts water. It can cause concrete to become more saturated with water than it would otherwise. The presence of this extra water in freezing conditions can spell trouble. The volume of water increases by 9 percent when it freezes within the concrete matrix. The pressure of the growing ice crystals can cause the surface of the concrete to fail. It usually spalls off.

So - is it safe to say that in the area of the country where we get lots of freezing, this may be an issue ?

 

[chem geek]

Welcome to TFP!

This paper talks about salt recrystallization pressure that is what causes some salts to damage concrete and soft (porous) stone surfaces. It is the repeated splash-out and evaporation cycle that is the problem. In areas of the country where there are summer rains, these often wash away and dilute the salt. The bigger problems are seen in climates without regular rain and with higher evaporation rates such as Texas and Arizona. The quality of stone matters as well.

What your buddy said about salt being hygroscopic is not really the issue. If you are going to get freezing, then any splash-out of water even without salt is going to freeze and technically if there was salt then the freezing point temperature is lowered. After all, that's part of why salt is put on roads -- to lower the freezing point temperature to prevent icing. So I would separate out the winter freezing issue from the summer splash-out. Besides, during the winter when the pool is closed there shouldn't be any splash-out so no salt getting onto the concrete anyway.

As I noted in an earlier post, if you are concerned with salt splash-out, you can seal your concrete. We have concrete coping and hand-trowled concrete made to look like flagstone and we seal it every year even though our pool does not have a saltwater chlorine generator and is lower in salt (usually in the 700-1400 range, though, due to use of chlorine and some dilution each year).

 

[toofast]

Ok....I will dig into that paper, but looks like I need to buy it which is not that big of a deal.

I guess I am "freaking" out about the salt and concrete, especially since my pool installer is so against it in climates that freeze...and we do for sure up in Ohio. We also don't have a ton of rain in the summer normally...spring and fall for sure. But then again we don't have a super high evaporation rate. So who knows ?

I tend to be a science geek, so the salt absorbing into concrete then freezing, seemed like an accurate assessment of what might happen.

I certainly don't mean to be second guessing anyone, I am just struggling to totally understand what I might be getting into.

 

[JasonLion]

In most places, any splash out from the pool will be washed away by fall rains long before any freezing can happen. In practice concrete simply isn't at risk from SWG levels of salt anywhere except in the driest climates, and even there it just takes an occasional rinse off with a garden hose to take care of it.

 

[toofast]

Yep it makes sense, except the strange thing is, that in OHIO VERY VERY VERY few people have SWG - I think everyone is freaked because of what salt does to the roads.

I talked to my concrete guy again...his thoughts are this:

1) concrete absorbs water, period - unless sealed all the time.
2) if the water contains salt, it will absorb into the concrete as well.
3) in the fall, even though the surface water is washed away, rain will continue to absorb and mix with the salt crystals already absorbed, as you can't get rid of them
4) ALL THE ABOVE MAY LEAD TO PREMATURE CONCRETE / REBAR FAILURE

Technically this makes sense....but I hear all of you saying in reality it is not true.

Do we/you have any feel for how many people in FREEZING Climates have SWCG systems vs. not...as once again it is not the salt on concrete that hurts, but the freezing in the winter combined.

If I am making everyone crazy....sorry !

 

[mrshanes]

Do we/you have any feel for how many people in FREEZING Climates have SWCG systems vs. not...as once again it is not the salt on concrete that hurts, but the freezing in the winter combined.

I'm in WV and we have plenty of freezing weather. I'm going on 3 years with a SWG and at least 10 feet of concrete on all sides of my pool. It's still rather new, but no concrete issues yet. As I said earlier, my only issue is the salt calcifying on the railings where they go into the anchors in the concrete. I take them out each winter and have to clean them really well. No rusting, just a pain.

Good luck with your decision.

 

[toofast]

Ok thanks much, this is the kind of real world feedback I am looking for...any more keep em coming!

 

[Cathy9887]

I'm just west of St Louis where it freezes a lot in the winter, yet SWG pools are very popular now. According to our installer, over half the nee pools they installed in the last 2years have been SWG. And I know 2 friends who converted just this year. I realize this doesn't help for the long term results, but I wanted to mention it since we're a freezing climate & they are DEFINITELY being installed a lot.

 

[BobbyR]

We live in Toronto and salt water pools are very common here. I'd say most new pools are done that way around here. Ours isn't salt but all the other pools on the street are. Haven't heard anyone complaining of salt damage to surrounding stone and concrete. That said, I decided against salt when we built our pool in 2005 because of fears of corrosion of the steelwork in the pool, not damage to the surrounding stonework. These fears were probably unfounded but that was my reason at the time.

 

[KBKilgore]

We started having problems with our stamped concrete crumbling around our salt water pool after the first year! It is starting to look bad. I would never do it again and really don't know what the answer is. We have sealed the concrete....always rinse the area. I feel we should have been warned by someone! The pool company or the concrete guy?
DON'T DO IT!