New(er) Hot Tub Trouble

[AClogston]

Hello everybody,

Our resort had a new indoor hot tub built a few months ago and I've been having a couple issues with it.

Ours is the only multi-tier hot tub in the whole state, and now I know why, this thing is a pain! The pH is constantly on the rise due to the aeration of the three waterfalls, not to mention the ridiculously powerful 3HP jet pumps that came with it. When the jets are on, a large mass of soapy smelling foam collects where the jets converge. When the jets are off it dissipates in a couple minutes, but it is annoying and I'd like to eliminate this.

Here's the latest set of test results:
Temp = 102
Bromine = 5.0
pH = 7.8
Alk = 30
CH = 250

While the ph and alk are off from ideal levels, this is almost spot-on on the CSI.

Every morning the pH is 8.0 and we have to add muriatic acid manually, this means the alkalinity is constantly low. Does the pH always being on the high side have anything to do with the foam? I know it's mostly caused by oils, lotions, etc., but is the bromine fighting (and failing) to keep up because of the higher pH? The water isn't cloudy, so it seems like the bromine's doing it's job.

I wanted to install a peristaltic pump to feed muriatic acid continuously, to keep the pH in range, but I don't know if this would help the situation. We've been following the WRI and the foam was gone for a couple days after the refill, then came back just as strong. The bather load wasn't all that high during this period either. I also change the filters every other day (every day at one point) and this seems to have no effect on the foam.

I've heard on here before that some people just have to have a lower alk and higher pH, but both levels are above or below the listed state code (ph max = 7.8, alk min = 80).

What should I be doing, aside from forcing every person to shower before using the hot tub at gunpoint, that is?

 

[chem geek]

One thing you can do to help control the rate of pH rise is to use 50 ppm Borates, assuming the state regs allow it. It's in products such as ProTeam® Gentle Spa (some report that this isn't really pH neutral) and ProTeam® Supreme PLUS as mostly boric acid which you can purchase separately from The Chemistry Store or from AAA Chemicals.

Is the spa a plaster one? If not, then you don't need to worry about the CSI being negative and don't need the CH to be that high -- usually 120-150 ppm is sufficient. On the other hand, higher CH helps to inhibit foaming though obviously not enough in your situation.

With your TA that low it's a bit surprising that the pH still rises, but with lots of aeration it is possible. At a TA of 30 ppm, the pH would technically stop rising from outgassing at around 8.0 which is pretty much what you've been seeing. If your regs actually require a minimum TA of 80 ppm, then you will be in really bad shape. Perhaps you can convince them that the borates are an alternative pH buffer without the side effect of rising pH from carbon dioxide outgassing -- that is, after all, the truth.

While the borates will likely help your pH issues, at least slowing down the rate of rise though may not reduce the amount of acid you need to add, I don't know what you can do to reduce the foaming since fundamentally it's from soap-like substances that people are bringing into the spa including swimsuits that aren't thoroughly rinsed. There are anti-foaming products available, but I don't know how well they work.

 

[PoolGuyNJ]

I would also ask what is the daily bather load and how often have you been changing the water?

Scott

 

[AClogston]

Thanks for the replies guys.

The state regs make no mention of borates, so I assume there's nothing to say I can't use them. Maybe that would be worth a shot.

The spa is indeed plaster, that along with the supposed reduction in foaming is why I thought a higher CH might help. To combat the foaming I've been using a self-floccing spa defoamer that seems to work and last longer than the regular defoamer, but instead of foam it makes the water appear kind of cloudy until the jets are turned off. So that isn't without it's own downsides. I've also tried using Zorbos, an oil scum absorbing sponge, and they haven't helped at all.

PoolGuy, the bather load in this spa varies greatly, but at its highest so far, it's at around 20 a day and at the lowest none, with many more low days than high. The spa is 3,200 gals and with 20 users a day the WRI is 52 days and the foaming happened within 4 days of me replacing the water, and I changed the filters every day at first to see if that helped. The draining, refilling, and reheating of it took over a day and I can't have it down more often than absolutely necessary.

 

[PoolGuyNJ]

Your user volume makes me suspect it's a body waste issue and an insufficient water change interval.

There's a lot of sweat and skin oils and such from 20 people that needs oxidation. This is where the foaming is coming from. The bromine alone won't do it. I would increase the shocking intervals, perhaps as often as three times a day.

Scott

 

[AClogston]

Thanks again for your reply Scott.

The 20 users a day figure is a really high estimate, in fact I'd say it only sees 20 users on Friday and Saturdays, and that's on a busy weekend. I can try to shock it more often and see if that helps.

Here's another question. To shock this hot tub, I use MPS shock, which is handy since you can swim in 15 minutes, so I might be able to do that 3 times a day, but it might get expensive. There's no way I can do that with Cal-Hypo shock, because it would result in too much downtime (which makes my General Manager hate me). Will the MPS help for this 3 times a day shocking interval in eliminating the waste, or should I try using Cal-Hypo shock at night, every night, after the hot tub is closed?

Another piece of advice I found on a couple other websites was to use an enzyme product. I tried using Pool Magic, when we first started having the problem and that also seemed to make no difference.

I appreciate your time.

*EDIT*
Also, back to one my original questions. Would having the feeder pump installed for muriatic acid help the bromine in eliminating the waste on a continuous basis? It's my understanding that with higher pH the sanitizer works harder to achieve the same effect. So I thought the lower pH might help in this case, but I don't want to expend the time, effort, and money to install it if it isn't going to help.

 

[JamesW]

Trying to maintain a TA of 80 ppm in a hot tub with plenty of aeration is really not practical. It's unfortunate that the regulations would be written by someone who does not understand why this is a bad idea. It will be a constant fight trying to keep the pH down and the TA up.

You could use carbon dioxide to lower the pH without lowering the TA, but that's really an unnecessary expense.

If the tub were not plaster, then you could use a phosphate-based buffer to increase the TA without increasing the carbonates. You might be able to use some phosphate buffer in a plaster spa, but probably not enough to maintain an adequate CSI. Using too much will cause the calcium to precipitate out.

(11) The total alkalinity shall be 60 to 180 mg/L.
http://des.nh.gov/organization/commissi ... wq1100.pdf

This reference indicates that the TA can be as low as 60 ppm.

An ozonator might be helpful for your situation. You would need a model that removes the ozone before returning it back to the hot tub. Perhaps it would be helpful to contact DEL Ozone (or another manufacturer) to request a proposal.

CALL 800.676.1335 x 222
EMAIL [email protected]
VISIT http://www.delozoneaquatics.com

http://www.delozone.com/special-projects/index.php

http://www.delozone.com/files/comm-pool ... ov2010.pdf

http://www.delozoneaquatics.com/request-ozone-quote/

As far as pH and bromine goes, any pH below 8.0 will be fine as long as you are maintaining adequate bromine levels. Hypobromous acid has a higher pKa than hypochlorous acid and is therefore not as affected as chlorine is (assuming no cyanuric acid).

I wouldn't put a muriatic acid feeder on a hot tub. As I noted above, using carbon dioxide might be helpful in your situation.

The number of bromine tabs will have an adverse effect on the bromine as the levels of DMH build up.

 

[chem geek]

Since this is a bromine spa, whether you use MPS or chlorine to shock the tub is irrelevant. Either one will increase the bromine level to a high level so I don't understand the comment about being able to swim in 15 minutes. That rule is for using MPS in a chlorine pool, not in a bromine spa that has bromide that will convert to bromine after adding MPS.

Anyway, chlorine often does a better job keeping the water clear so maybe it will help reduce foaming if you shock with it instead, but I wouldn't use Cal-Hypo since your CH level is already high. Remember the following chemical facts that are independent of concentration of product or of pool/spa size:

For every 10 ppm Free Chlorine (FC) added by Trichlor, it also increases Cyanuric Acid (CYA) by 6 ppm.
For every 10 ppm FC added by Dichlor, it also increases CYA by 9 ppm.
For every 10 ppm FC added by Cal-Hypo, it also increases Calcium Hardness (CH) by at least 7 ppm.

You can try using chlorinating liquid or bleach (both are sodium hypochlorite) to shock and yes, do that at night to have some hope of the level being somewhat lower the next morning. Worst case, if it's not, you an always add a neutralizer -- even hydrogen peroxide can be used for that purpose if you don't want to use sodium thiosulfate or similar product.

As for pH and bromine, it is still active at higher pH so I don't think lowering the pH is going to help that much. By the way, how are you maintaining the bromine level in the spa? Are you using lots of bromine tabs? Or did you initially establish a bromide bank (50 ppm or so) and then are adding an oxidizer to create bromine (and if so, what oxidizer -- MPS or chlorine and if chlorine, what type)?

 

[AClogston]

The bromine level is maintained via a standard tablet feeder and it gets shocked with MPS once or twice a week. The bromine level is usually around 5-6ppm (upper end of the limit), and I was hoping that keeping it constantly higher would eliminate the need for shocking as often and help keep the foam at bay. This doesn't seem to be the case, though keeping the bromine higher does help keep the pH in check slightly.

I'm going to do a full drain and refill tonight, but the last time I did was less than a month ago (1/2/12), and I'd like to not have to do it any more often than the WRI (52 days @ 20 users/day) suggests. This time 'llI try shocking it more often, like Scott suggested, and see if that helps. I've also ordered a couple quarts of Pool First Aid to try, should the foaming arise as quickly as it did last time.

 

[PoolGuyNJ]

At 20 people per day, daily shocking is a must. Water changes no less than every week.

I would use bleach or 12%, not MPS.

Do not skimp on a commercially operated hot tub, which you are doing, whether you know it or not.

Scott

 

[AClogston]

What are the advantages of using Sodium Hypochlorite for shocking? Doesn't it raise pH (which I'm constantly battling to keep lower), whereas MPS does not? Don't it and bleach accomplish the same thing.

I'm trying not to "skimp", but completely draining a 3,200 gal hot tub every week is a time consuming and potentially pricey proposition. I know the WRI of 52 days might be a little on the optimistic side, to say the least, but draining every week is daunting, and I can already hear the complaints (from guests and my General Manager) over all the downtime.

 

[JamesW]

Instead of periodically doing a full drain and refill, you might want to do a daily refresh by draining 200 to 400 gallons per day and refilling. That would limit downtime and keep the water fresher.

 

[AClogston]

Every day I have to add I'd say about 50-75 gallons of fresh water anyway and that also has no effect and it also puts the temp down to about 90, so I think doing so with 200-400 gallons daily would leave in a constant state on "not hot enough", which gets me yelled at.

 

[JamesW]

Every day I have to add I'd say about 50-75 gallons of fresh water anyway and that also has no effect and it also puts the temp down to about 90, so I think doing so with 200-400 gallons daily would leave in a constant state on "not hot enough", which gets me yelled at.

75 gallons is only 2.34 % of the tub's volume, so it won't be enough to do very much in terms of diluting any contaminants, or lowering the water temperature. Even if the water is ice cold at 32 F, adding 75 gallons would only lower the temp. to 100.36 F

If you add 100 gallons of water at 32 degrees Fahrenheit to 3,100 gallons of water at 102 degrees Fahrenheit, the result would be 3,200 gallons at 99.8 degrees Fahrenheit.

Even if you add 400 gallons of 32 F water to 2,800 gallons of 102 F water, the result will be 3200 gallons of water at 93.3 F.

You would have to add 548.57 gallons of 32 F water to 2651.43 gallons of 102 F water to lower the temperature down to 90 F.

So, something is off in your calculations. What is the fill water temperature?

You might have to get a larger heater for the tub to allow you to reheat faster. That way, at the end of the day you could drain, refill and have the tub reheated quickly. An 83 % efficient 300,000 Btu per hour heater will heat 3,200 gallons 9.33 degrees Fahrenheit per hour.

Commercial hot tubs are especially difficult to manage due to the high bather load relative to the water volume. You might need to consider using UV or ozone to obtain consistently good quality water.

 

[JamesW]

You might be able to rig up some sort of continuous water exchange. If you simultaneously added and removed 1 quart per minute, that would refresh 360 gallons per day, which is 11.25 % of the water volume. Perhaps you could pull some of the makeup water from the pool since it is already balanced and heated.

There are multiple ways of doing this, and it makes things more complicated. You would have to make sure that the chemical and water levels remained consistent. Heat should not be too much of an issue based on how slowly the fresh water is added.

If the tub has an overflow, then just adding the fresh water and allowing the excess to go out the overflow should work fairly well.

 

[AClogston]

Thanks for your effort James.

I think I'm going to try draining the upper tier (roughly 850 gallons) every other day, after the spa has closed for the night, in addition to more frequent shocking. If needed I'll also do a full drain refill weekly/bi-weekly.

There's no way my higher-ups are going to give me the go ahead to buy any other equipment for this thing (ozone, UV, etc.) , so water replacement is basically my only option. I'm going to give a product called Perfect Spa a shot too.

 

[JamesW]

If you plumb a valve from the spa suction to the pool return, you could quickly fill the spa by opening the valve and closing the other spa suctions. Perhaps you could use half pool water and half fresh water. If you plan ahead, you could overfill the pool so that it is the correct level after you fill the spa.

What heater do you have on the tub?