Starting up a hot tub

[dogsbody]

@DangerBoy - Hey, Roj.

I'm in a similar situation, but worse. New install of an old Dynasty tub out in the woods, and filled with soft water simply because it was convenient (i.e. the house's plumbing) and nobody told me otherwise. Now that I'm trying to get the chemistry right I couldn't get the pH to come down, so I drained and refilled with hard (well) water. I mean, really hard. My old and in need of calibration TDS meter says 900ppm (for reference, it reports our RO water at 40ppm). So where do I go from here? I gather that 200-300ppm of Ca is optimum, but dog knows what else is in there along with it, including iron.

I don't consider using RO water a practical option as a starting point, given the low production rate. I don't know how people who say they do it do it.

Suggestions for getting on track would be most welcome.

 

[DangerBoy]

@dogsbody 900 ppm TDS is actually fairly low for well water or let's just say it is not extraordinarily high and actually would be considered low in some areas. The question is, what does your water chemistry look like? What type of water is it? The major cation could be sodium or could be Ca-Mg or it could have a mixture of both. The major anion could be Bicarbonate but also could be sulphate or even chloride. It depends so much on the local geology and what types of rocks and sediments are present in the subsurface there.

What might be helpful, informative and worthwhile is to go to an environmental lab, ask for a bottle for doing a routine water analysis and a small cooler and an ice pack. They should give those things to you on the understanding that you will be bringing them a water sample to analyze. The bottle they'll give you will likely be either a 250 or 500 ml plastic bottle. Maybe get a chain-of-custody form from them as well. You can use that to order the analysis you want.

Let your tap or hose run quite a while before you collect your sample. You don't want the sample to be biased by any stagnant water that might be in the wellbore if your well hasn't been pumped for a while. What you want is a sample that is representative of the water that's in your aquifer so pump the well for quite some time to purge any stagnant water that might be in the well and to ensure that your sample is of water that is fresh and straight out of the aquifer.

Place the sample in the cooler packed with ice or with the frozen ice pack the lab may have supplied you with when you got the bottle. Get the sample into the lab as quickly as you can. I think the holding time limit on a routine water sample is something like 48 hours. After that, the sample starts to degrade and the results aren't as accurate any more. Get the lab to run a routine water or routine potability analysis on the sample. That will give you the concentrations of all the major ions (Ca, Mg, Na, K, HCO3, CO3, SO4, Cl) and a few metals like iron and manganese which are important to know the concentrations of. It'll also calculate TDS, Total Alkalinity and Calcium Hardness and give you a few other parameters as well. If you're in the US, make sure they report the results in mg/L (ppm) and not grains per gallon. Grains per gallon has to be the most stupid and useless set of units I've ever heard of. And just ask for regular turnaround on the sample results. No sense paying a premium for expedited results unless you're in a real hurry to see them.

Once you get the test results you will be in a much better position to know what you're dealing with and whether you should be using your raw, untreated well water or if you should go with using the RO water from your house. You might want to do that if you find out you've got really high iron and/or manganese in the well water. If either of those metals is in high concentration in your well water you will likely run into problems with staining and the metals precipitating out as oxide unless you've got some sort of treatment system other than RO for knocking those metals out.

If you want, you can forward the test results to me and I can help you interpret them and understand what they mean. I look at that type of test result everyday as part of my job so it would be no problem for me to do that.

 

[dogsbody]

Let your tap or hose run quite a while before you collect your sample. You don't want the sample to be biased by any stagnant water that might be in the wellbore if your well hasn't been pumped for a while. What you want is a sample that is representative of the water that's in your aquifer so pump the well for quite some time to purge any stagnant water that might be in the well and to ensure that your sample is of water that is fresh and straight out of the aquifer.

Well (oops, pun...), it's not even that straightforward. You probably don't recall these details from when we were talking about my well a few years ago, when it was acting weird and we thought the level of the aquifer may have dropped (it turned out to be a pump that was acting very strangely in addition to being much further from the bottom of the bore than necessary), but getting "fresh" water from the well won't be representative of the water we use, because the well fills a 1200gal cistern in the basement, and we pump to the house plumbing from there. That was done at the suggestion of the neighbor we bought the land from, as the well's production was marginal and we were sharing the aquifer, so we throttled the well to a couple of gpm and use the cistern as a buffer. That gives the water some time to settle, as well as (I suspect) outgas, as I'm pretty sure that there's a lot of gas dissolved in there - CO2 is my suspicion, as it isn't sulfurous or otherwise smelly, or flammable. Which is a good thing, given that we're in the middle of an awful lot of sour gas, the Quirk Creek plant is just a few miles down the road, etc.

And as I mentioned in the other thread (it's a little hard to keep up with - I initially jumped in here, and when I didn't appear to get any response for a few days I started a new one - which got merged into a different thread, "Starting up a hot tub"), using RO isn't practical - I only have a small domestic unit used in the kitchen and it'd probably take a month to fill the tub from it. So the choice is hard, soft, or a combination of the two.

 

[dogsbody]

Okie-doke, I'm back - with a brand spankin' new Taylor test kit.

In our previous episode the tub was drained and refilled with hard (well) water. But there's a leak (that I'm going to get on ASAP, now that I also have the Plast-Aid repair kit), and in the meantime I've been topping it up with soft water. So there's a slowly-growing mix of the two in there (~425gal).

My initial state is:

pH => 8.0 (it's a little darker pink than the highest on the scale)
TA = 750ppm (based on the 10ml sample test)
CH = 75ppm (ditto)

I think that's about all I can test at this point, but may be wrong. Given that starting state, what should my first step be? Bringing the pH down? Or perhaps adding dichlor so I can get an initial CYA measurement, then lower the pH?

 

[Mdragger88]

Okie-doke, I'm back - with a brand spankin' new Taylor test kit.

In our previous episode the tub was drained and refilled with hard (well) water. But there's a leak (that I'm going to get on ASAP, now that I also have the Plast-Aid repair kit), and in the meantime I've been topping it up with soft water. So there's a slowly-growing mix of the two in there (~425gal).

My initial state is:

pH => 8.0 (it's a little darker pink than the highest on the scale)
TA = 750ppm (based on the 10ml sample test)
CH = 75ppm (ditto)

I think that's about all I can test at this point, but may be wrong. Given that starting state, what should my first step be? Bringing the pH down? Or perhaps adding dichlor so I can get an initial CYA measurement, then lower the pH?

Are you sure about the ta ?
Its a 25 ml sample test - each drop counts as 10ppm
Give that a redo
Add 10ppm worth of 99% dichlor- this will get you some fc & about 10ppm worth of cya.
It will also lower the ph some.
Then re test & work on the ph (& subsequently ta) with Muriatic acid. Using
PoolMath
Lowering ph to around 7.2 then aerating back to 8.0 and repeating the process - each round of this will lower the ta.
In a spa this happens quickly- a round of aeration may only take 15-30 minutes especially with a high ta.
As you get further along (ta gets lower) the bites each round takes out of the ta will get bigger in my experience. You don’t have to get to a ta of 50/60 today. Just work on it as you have time.

 

[dogsbody]

Are you sure about the ta ?
Its a 25 ml sample test - each drop counts as 10ppm
Give that a redo

Quite sure. The instructions state:

"When high TA is anticipated: Use 10ml sample, 1 drop R-0007, 3 drops R-0008, and multiply drops in Step 4 [R-0009] by 25."

I anticipated high TA because this is (mostly) well water from the foothills at around 4000 ft. The colour change took place at 30 drops.
The only surprise to me is that the CA hardness is as low as it is, but not too much of a surprise, as @DangerBoy suggested that it may
be the case, and he knows the geology of this area intimately.

Add 10ppm worth of 99% dichlor- this will get you some fc & about 10ppm worth of cya.
It will also lower the ph some.
Then re test & work on the ph (& subsequently ta) with Muriatic acid. Using
PoolMath
Lowering ph to around 7.2 then aerating back to 8.0 and repeating the process - each round of this will lower the ta.
In a spa this happens quickly- a round of aeration may only take 15-30 minutes especially with a high ta.
As you get further along (ta gets lower) the bites each round takes out of the ta will get bigger in my experience. You don’t have to get to a ta of 50/60 today. Just work on it as you have time.

Thanks - will be out to get supplies today.

 

[Mdragger88]

If your ta is really that high you may just want to carefully manage ph to keep it in the high 7’s and not worry about it too terrible much. Quite a battle to get ta to under 100 from 750

 

[dogsbody]

Yes, my first goal will be simply to get the pH within measurement range rather than (what I think is somewhat) off the top of the scale.

The other tool I have available is diluting the (present) hard water with soft, or starting over with soft water. I'll just have to see how much of a wrestling match it is. I expect much trial and error.

 

[mknauss]

Water softener does not remove TA.
Why do you have a water softener if the CH of the fill water is 75 ppm?

 

[dogsbody]

Excellent question. The fact is that (notwithstanding the measured 75ppm CH) the well water here fouls everything to an unbelievable extent. Every plumbing fixture is covered in white deposits within months, if not weeks. If I put a double-boiler on the stove, by the time the chocolate (or whatever) is melted, the lower pot will be dusted white. Our well water is a real hassle that a conventional NaCl softener solves. So - and as I wrote previously - I've always assumed the majority of that hardness to be coming from calcium compounds, and was surprised when @DangerBoy told me it was probably other stuff. It might, as he suggested, be useful (or at least interesting) to have a lab do a full analysis of it, but unless there's something about it that creates problems for this tub, I can do without the expense.

 

[dogsbody]

This is exactly the problem I'm having as well - my TA is 550ppm and it's going to take days to bring the pH down below 8 if I follow Taylor's "Acid Demand" test and add muriatic 150ml at a time. I'm on my first go at this and it's good to see you post some kind of estimate of what it's going to take - it would appear that in my case it'll be more than a litre, so it would appear to make sense to bump my additions up to 250ml at a time until the pH budges.

Unless someone can explain why that's a bad idea.

 

[wickflair23]

This is exactly the problem I'm having as well - my TA is 550ppm and it's going to take days to bring the pH down below 8 if I follow Taylor's "Acid Demand" test and add muriatic 150ml at a time. I'm on my first go at this and it's good to see you post some kind of estimate of what it's going to take - it would appear that in my case it'll be more than a litre, so it would appear to make sense to bump my additions up to 250ml at a time until the pH budges.

Unless someone can explain why that's a bad idea.

I got a really good suggestion from a user on reddit. See below

If you mix the muriatic acid solution–aka hydrochloric acid aka HCl(aq)–with water in a 5-gallon bucket first, you can probably add more at once. The important things here are to add the acid to the water and not vice versa, to dilute it at least 1 part acid solution to 10 parts water, to wear PPE (acid-resistant goggles, gloves, and respirator), and to not splash it while mixing. As you've discovered, the fumes from 31.45% HCl are corrosive, and they can kill you if inhaled.

If you need to add 26 fl oz of 31.45% acid, that means you'll need at least 260 fl oz of water, which is a little over two gallons of water. With the acid solution added, that's 2.2 gallons and weighs about 19 pounds. So, you still may want to do it in two or more batches, depending on how much weight you can lift easily to tub height.

By the time you dilute it that much, it's under 3% acid and its density is only 1.01g/mL, almost exactly that of water itself, so you won't need to worry about it sinking and damaging your tub before it mixes in with the tub water. However, 3% HCl can still cause skin and eye irritation, so continue to be careful with it when pouring it into the tub. Make sure you run the circulation pump while you're adding it.

 

[mas985]

I got a really good suggestion from a user on reddit. See below

If you mix the muriatic acid solution–aka hydrochloric acid aka HCl(aq)–with water in a 5-gallon bucket first, you can probably add more at once. The important things here are to add the acid to the water and not vice versa, to dilute it at least 1 part acid solution to 10 parts water, to wear PPE (acid-resistant goggles, gloves, and respirator), and to not splash it while mixing. As you've discovered, the fumes from 31.45% HCl are corrosive, and they can kill you if inhaled.

If you need to add 26 fl oz of 31.45% acid, that means you'll need at least 260 fl oz of water, which is a little over two gallons of water. With the acid solution added, that's 2.2 gallons and weighs about 19 pounds. So, you still may want to do it in two or more batches, depending on how much weight you can lift easily to tub height.

By the time you dilute it that much, it's under 3% acid and its density is only 1.01g/mL, almost exactly that of water itself, so you won't need to worry about it sinking and damaging your tub before it mixes in with the tub water. However, 3% HCl can still cause skin and eye irritation, so continue to be careful with it when pouring it into the tub. Make sure you run the circulation pump while you're adding it.

You should still not go below a PH of 7 no matter what method you use to add the acid.

Also, this is really no different than slowly pouring the more concentrated acid into a running spa in front of one of the jets. In both cases, the acid gets diluted very quickly and should not cause an issue to the surface.

 

[dogsbody]

Sure - that's all obvious to anyone who passed high school chemistry. Since I'm really trying to get my hot tub legs under me for the first time, I'm going to see if I can get into the neighborhood 250ml at a time, and if that exercise shows that a litre or more of acid is going to be needed for a fresh fill, will pre-dilute it in a five-gallon bucket. Lifting it (safely) isn't an issue, as the tub is sunk into the deck.

High TA sure does buffer the stink out of the acid, though. It's going to be interesting to see how it behaves when I (finally) hit the threshold.

 

[dogsbody]

You should still not go below a PH of 7 no matter what method you use to add the acid.

Dude, I'm just trying to get it below 8 .

 

[wickflair23]

Dude, I'm just trying to get it below 8 .

Worked well adding every 10-20 minutes and testing the TA every 3-5 times. Aeration the entire time.

 

[dogsbody]

Worked well adding every 10-20 minutes and testing the TA every 3-5 times. Aeration the entire time.

Was that with the 8oz doses you suggested above?

 

[wickflair23]

Was that with the 8oz doses you suggested above?

Only 2-3oz the first 2 fills. This time I started with 7oz and then 2-3oz after that.

 

[dogsbody]

Wow - that was a workout. The pH finally dropped, landing at 7.4 , though it looks like it's bouncing up a little... 7.6 . And with it came a TA of 75 and CH of 20, so everything now looks to be within the range of sanity, and I can finally begin to address the Cl. But it took more than 1.6 litres of muriatic acid in 425 gal. of softened well water. I expect that with the next water change I'll toss in 1.5 litres right off the bat, then tune it from there.

[edit]

Now, stop me if I'm missing something, but where should CH actually be? @Nitro's sticky says 130-150. However, the pool calculator (web version) says 250-650 - a big difference. Why the discrepancy? What should my target actually be?

 

[JoeSelf]

You need just enough to keep foaming at bay. If I recall correctly above 100 should do the trick.