Is Spa Water Really Safe For Garden?

[arnspa]

We have a Master spa H2X Crosstrainer 2, 1300 gals. I've drained it into barrels and was planning to use it to water trees in the yard. (We have 4-5 months zero rain) I've read here posts that say Sure, no problem, but elsewhere I've seen warnings that plants cannot tolerate such water.

I had been putting chlorine, etc, in it for 6 months. I let sit for a week before draining, open to the sun. In the barrels, after 2 months I see that what look like salt rings have condensed near the bung hole. I worry that this stuff may be much too salty.

Is there any way of testing or judging this? We have fruit and citrus trees I don't want to harm. Still, I hate to run all this water down the drain. Any wisdom about this?

Thanks,

[Dr. Spa]

There's WAY less chlorine in your spa water at this point than in any municipal water throughout the country. Water the trees is fine.

Where have you seen ANYTHING saying it might be bad for the plants???

[arnspa]

Thanks for your reply. It's not chlorine I'm worrying about so much as salts. I've been using Sodium DsTD. I understand the chlorine burns off, but what's left?

Some garden sites warn about using salt water from (fish) pools and spas. One says it's OK for grass but not edibles.

I think it's may be typical of garden sites to be overcautious, and spa sites to be the opposite.

I've read that Bermuda grass can take much more saline water than, say, Kentucky blue, but I have no idea what the tolerance is for lemon, pear, plum, apple, persimmon, avocado, etc. I'm reluctant to experiment with such trees. Still, I'd hate to be putting 2600 gals down the drain every year when we could use that water if it's safe enough.

Is there an easy way to measure water salinity, and to tell whether it will harm trees? Are there Ag sites that have info on salinity, etc?

Thanks again,

[bart6453]

Thanks for your reply. It's not chlorine I'm worrying about so much as salts. I've been using Sodium DsTD. I understand the chlorine burns off, but what's left?

Some garden sites warn about using salt water from (fish) pools and spas. One says it's OK for grass but not edibles.

I think it's may be typical of garden sites to be overcautious, and spa sites to be the opposite.

I've read that Bermuda grass can take much more saline water than, say, Kentucky blue, but I have no idea what the tolerance is for lemon, pear, plum, apple, persimmon, avocado, etc. I'm reluctant to experiment with such trees. Still, I'd hate to be putting 2600 gals down the drain every year when we could use that water if it's safe enough.

Is there an easy way to measure water salinity, and to tell whether it will harm trees? Are there Ag sites that have info on salinity, etc?

Thanks again,

well...after much debate and showing my wife the posts from this site and the discussion of chlorine going to basically zero in a few seconds....my wife let me drain my tub down the hill(through her lilly garden) on the last refill. the free chlorine was at .5 ppm and combined was at basically zero. The water had borates added, and not much else. TA was at 80.

The rest of the story.....I have been hearing about it for the past month. All her lilly's and hostas down the hill have severe burn and are extremely growth retarded. Seriously.......12 feet wide by 100 feet long....it's bad...really bad. So...just a heads up....some things are sensitive. My grass is just fine though.

[chem geek]

If someone uses Dichlor at around 4 ppm FC per day then after 3 months this results in around 288 ppm salt (sodium chloride) and 324 ppm Cyanuric Acid (CYA). There is probably also calcium based on Calcium Hardness (CH) of around 100 ppm or so.

If someone uses Dichlor-then-bleach at 4 ppm FC per day, then after 6 months this results in around 1152 ppm salt and the same 30 ppm or so CYA that you initially built up and the CH as noted above.

I would be very surprised if the 0.5 ppm FC was the culprit given that many water systems have 1 ppm FC or more (nowadays, many have switched to monochloramine so around 1 ppm CC instead). So if you were using Dichlor-then-bleach and didn't change the water for 6 months then my best guess is that the problem is from the salt. As for borates and plants, see here where you should read the section on Toxicity and see if the symptoms are the same a what you saw. Note that 50 ppm Borates (Boron) is 50 mg/liter and that it looks like much above 5 mg Boron / kg soil can be a problem. So if you were watering such that there was more than 100 ml (3.4 fluid ounces) over 2.2 pounds of soil, then that could be the issue.

Richard

[bart6453]

If someone uses Dichlor at around 4 ppm FC per day then after 3 months this results in around 288 ppm salt (sodium chloride) and 324 ppm Cyanuric Acid (CYA). There is probably also calcium based on Calcium Hardness (CH) of around 100 ppm or so.

If someone uses Dichlor-then-bleach at 4 ppm FC per day, then after 6 months this results in around 1152 ppm salt and the same 30 ppm or so CYA that you initially built up and the CH as noted above.

I would be very surprised if the 0.5 ppm FC was the culprit given that many water systems have 1 ppm FC or more (nowadays, many have switched to monochloramine so around 1 ppm CC instead). So if you were using Dichlor-then-bleach and didn't change the water for 6 months then my best guess is that the problem is from the salt. As for borates and plants, see here where you should read the section on Toxicity and see if the symptoms are the same a what you saw. Note that 50 ppm Borates (Boron) is 50 mg/liter and that it looks like much above 5 mg Boron / kg soil can be a problem. So if you were watering such that there was more than 100 ml (3.4 fluid ounces) over 2.2 pounds of soil, then that could be the issue.

Richard

I am fairly certain that it was the borates.....But does confirm that not all spa water is safe for everything. Not a biggie for me, just looks bad...but if it was a garden full of expensive stuff...I would be pretty dissapointed for sure.

[arnspa]

I have lately got a TDS (total dissolved solids) meter ($20), and found some info at the Texas A&M website, Water Management Guidelines for Nursery/Floral Producers, and at USDA Handbook 60.

Tap water at my house is 40-50 ppm. Rain water collected from my roof is 140-150. The water currently in our swimspa (after 10 weeks) is 500. The water I saved in barrels from our last water change (6 months) measures over 1100 ppm.

The A&M site rates irrigation water as Excellent = 175, Good = 175-525, Permissible = 525 -1400, Doubtful = 1400 - 2100, Unsuitable = >2100.

USDA Handbook 60, pp 65-67, shows some plants to be much more sensitive than others. Avocado and lemon most sensitive, then stone fruit, then apple and pear. Figs and olives are more tolerant, date palm most tolerant. They give other tables for vegetables and grasses. Bermuda is more tolerant than perennial rye.

It was primarily fruit trees that I wanted to save the spa water for. Although 1100 ppm falls within the "permissible" range it's at the high end, and too close to "doubtful" for me to take the risk with fruit trees. (Also, this water has been standing 10 weeks. I measured only at the top of the barrels. If the salt settles at all, it may be much more saline than my numbers indicate.)

The one time I ran the water through a soaker hose to roses and yard plants, there was white residue (salt) left on it.

Also (embarrassing report): Last fall I planted two 5 ft avocado. One was injured by frost but recovering, the second was fine. Then in July, I watered them once with the spa water, not a lot, a couple gals.. The next week I gave them a big drink of rain water. In 3 days they were dead. My best guess is that the rain water carried the spa water and that killed them.

In any case I won't be using the spa water for my trees, and I sure wish I had not read so many posts here saying it was just fine. Maybe for others, not for me.

My next project is to see if I can I can plumb the barreled water to our toilets.

[arnspa]

If someone uses Dichlor-then-bleach at 4 ppm FC per day, then after 6 months this results in around 1152 ppm salt and the same 30 ppm or so CYA that you initially built up and the CH as noted above.

Richard

Richard, Please see my last post here, at bottom. With a Master swim spa, I'm trying to keep the chlorine level about 1 ppm, the 1300 gal. spa has an ozonator. I take your post above to imply that there's no advantage for me to switch to a Dichlor/bleach regimen? That is, with Dichlor for 6 months I got 1100+ ppm DST. And with bleach I could expect 1152?