In-ground spa aeration (not another aeration post!)

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alexsmith1

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Oct 11, 2018
33
Gold Coast, Australia
Hi all,

Newly home owner (no pool/spa experience) with a 5,000L (1320 gallon) in-ground spa with an aeration problem.
* No heater
* SWG
* Onga LTP750 pump (280LPM / 74 GPM) - only 1 speed mode
* Pump runs daily for 45 minutes
* Pebble creek spa with waterline tiles (grout) - Not my spa but something like this http://2.bp.blogspot.com/-l_WBVPbxxjs/TWkjdLHqsfI/AAAAAAAACIY/C0M7JWL7YmQ/s1600/SSPX0124.jpg )
* Spa was re-surfaced 3 months ago and hasn't been used!!

The spa is pretty much a glorified pool (a lot smaller) with jets. My problem is I can't bring down the pH. I'm constantly adding Hydrochloric acid AKA Muriatic acid daily! I believe the issue is the spa doesn't have a "non jet mode". With a venturi system hence why the rise in pH because of aeration!

I'm adding about 1/2 - 3/4 cup of acid daily to keep the pH under 8.0-8.2. Most days it's around the 8 mark!!
Obviously with the fighting pH I'm fighting TA. Which is around the 50-80 mark depending on how much acid I've put in.

I guess my question is:
1) I can't seem to stop the aeration out of the jets - is there anything that can be done? I've checked the pump seals & pipes no issues. My gut feeling is the internal pipes have a venturi system which doesn't allow me to turn off the "bubbles".
2) Will a variable pump help?
3) Do I need to run the pump daily to turn over the water if it's not being used?

Here are my results from last weeks pool shop test. I have a test kit that I check pH & TA daily!
FC: 1.89 (low need to bring FC up a little)
TC: 2.18
pH: 8.2
AK: 97
Adjusted Alkalinity: 76
Hardness: 354
CYA: 64
Salt: 7000 (yes I know way too much salt in the spa.. I need to bring it down to 3500)
Iron: 0.1
Copper: 0
Phosphate: 40

I have a pool (completely seperate - its own pump etc) with NO problems. Water is balanced to a tee!

Any help/suggestions would be greatly appreciated. thanks!
 
New plaster makes your ph increase for awhile. May want to try boric acid 50ppm to help stabilize the PH a little. I use the boric acid in my spa after we close the pool in the fall and it helps a little. Also if it is a venturi system there is usually air intake ports somewhere. Closing them would create less bubbles.., at least that's how my system is setup.
 
@wjr75, thanks for the prompt reply! I'll suss out if any shops in Australia sell boric acid (never heard of it before). I have tried closing the air intake ports however theres still a number of bubbles somewhere. I'm wondering if the pipe has a "built in venturi system"? Is that possible?

Do you run your spa pump daily? Can I go without running it every day considering the size - 5,000L. thanks!
 
Curing plaster, a SWG, and constant aeration all combine to pretty much ensure you will have an insatiable thirst for acid. About all I can suggest is to target 7.2 when calculating doses, if you aren't already.

My spa has an air intake pipe that I capped with an old spray paint cap. I can remove it easily if I ever want more bubbles. Note that it didn't eliminate bubbles completely. I suppose if I glued a cap on, it might.
 
Duda Diesal sells boric acid granules in the US..not sure if you can get these from them in Aus. When I have the spa just open in the fall after closing my pool I run the spa 1.5 hours in the morning and 1.5 hours in the evening...probably over kill. I also have it covered.
 
Geday Alex and welcome aboard, one of the fundamentals of TFP is self testing and for that us Aussies are a bit limited. The best kits we can get are from ClearChoiceLabs, CCL - Total Pool Water Testing Kit, Fresh Water Clear Choice Labs Most local pool shops sell an Aussie Gold 4in1 which has a good pH comparator and may be the one you have. The OTO FC test in the 4in1 is a bit useless, you need the FAS-DPD FC kit from CCL. If your up to it you can import a Taylor K2006 or K2006C and a Speedstir from PoolVacParts, the Speedstir is worth gold; http://www.poolvacparts.com/

Your spa pH is most likely constantly rising due to the new finish. Airation and high alkalinity will speed up the rate of rise but isn’t driving it. Target a low TA, ~60ppm. I got my boric acid from eBay. Testing for borates is difficult, TFP doesn’t advocate for guess strips (test strips) but you can get the Lamotte borate strips from hear; https://www.teststripsonline.com.au/

Your test result are typical store results - too precise. Rounded you get FC 1.5ppm, CYA 70ppm, pH8.2?, TA 100ppm, TH(?) 350ppm. Stick with your pH rests. We don’t adjust TA, you’ll end up over dosing it. That is most likely total hardness, we only care about calcium hardness, magnesium is way too soluble to cause any issues in a pool or spa.

I am the most sceptical about any LPS salt readings but there is a big difference between 7000ppm and 3500ppm. Salt levels that high will cause damage - don’t run you SWC above 80% until you get it down. I assume 3500ppm is your SWCG manufacturers recommended level? Is your SWCG indicating ‘high salt’?

You will need to run your pump enough to manage your FC. If you run it any less you’ll need to manage your FC with liquid chlorine - stay away from powdered chlorinated products or acid.
 
Hi @AUSpool, appreciate the reply!

I have been using the Aussie gold 4in1 (only for pH & FC) along https://www.mrpoolman.com.au/products/water-technix-5-in-1-test-kit-pool-spa-chlorine-bromine-ph-alkalinity-acid . Reason being the Aussie gold reports extremely high TA (incorrect) compared to pool shop and the water technix kit. I'll look at getting a CCL kit!

As mentioned, I think you're right about the finish (after speaking to various pool shops). I'm only running the spa (5,000L) for 30min a day - pebble creek, SWG. Should I run the pump longer to 'break in' the pebble creek? My biggest concern is my pH jumps from 7.3-7.8 within a day! I'm adding 1/4 of acid every second day to keep in check.. my wife and I are overseas for 3 weeks in a few months and I'm freaking out about the spa having excessive pH over this time!

Yesterday's pool shop spa readings (1/4 cup of muriatic acid was added previous day):
FC: 4.83
pH: 7.7 - comparable to Aussie Gold kit
TA: 70 - comparable to Water Technix kit
CH: 427
CYA: 73
Salt: 4533 - is high, SWG is at 20%. Should be around the 3500 mark as per manufacturers recommendation (as you mentioned). SWCG does indicate high salt if cranked up to 100%. I'm trying slowly getting rid of the salt haha!

Appreciate your help mate!!
 
Boric acid won’t reduce your acid demand, but it will let you add the acid less frequently which is still a win. As a bonus, it inhibits algae growth and I think the water feels nicer.

If you cannot find boric acid in Oz, check around for “Borax” in the laundry/cleaning supplies aisle of you local bigbox store. You’ll have to add still more acid with it since it is a base, but the pool calculator will show the proper amounts in the “Borates” section.
 

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alexsmith1 said:
Hi @AUSpool, appreciate the reply!

I have been using the Aussie gold 4in1 (only for pH & FC) along https://www.mrpoolman.com.au/produc...-pool-spa-chlorine-bromine-ph-alkalinity-acid . Reason being the Aussie gold reports extremely high TA (incorrect) compared to pool shop and the water technix kit. I'll look at getting a CCL kit!

As mentioned, I think you're right about the finish (after speaking to various pool shops). I'm only running the spa (5,000L) for 30min a day - pebble creek, SWG. Should I run the pump longer to 'break in' the pebble creek? My biggest concern is my pH jumps from 7.3-7.8 within a day! I'm adding 1/4 of acid every second day to keep in check.. my wife and I are overseas for 3 weeks in a few months and I'm freaking out about the spa having excessive pH over this time!

Yesterday's pool shop spa readings (1/4 cup of muriatic acid was added previous day):
FC: 4.83
pH: 7.7 - comparable to Aussie Gold kit
TA: 70 - comparable to Water Technix kit
CH: 427
CYA: 73
Salt: 4533 - is high, SWG is at 20%. Should be around the 3500 mark as per manufacturers recommendation (as you mentioned). SWCG does indicate high salt if cranked up to 100%. I'm trying slowly getting rid of the salt haha!

Appreciate your help mate!!
Click to expand...

If I were you I would use the Technix TA & pH reagents, and the 4in1 comparator and CH. CH doesn’t normally move that much so don’t worry about it much for now. The yellow OTO FC test is a bit useless to you. You don’t need to get the entire kit from CCL - just what you need, the FAS-DPD FC test is a must and you’ll need a CYA kit although be warned the disappearing dot CYA test is the most suggestive of them all. I’ll be comfortable to think you CYA is at 70ppm.

Both of my pools will go strait back to a pH of 7.8 when lowered to 7.2. I lower it occasionally to lower my TA. Don’t worry to much about leaving your poll for a few weeks, its still a few months out. You will find your pool will level off at a pH of 8.3 for a long time. There’s been lots of pools that have been poorly managed and left at 8.3 for much longer without any real long term damage.

Dont worry about chasing a salt level - listen to your chlorinator. It it says to much salt then lower your salt and similarly if and when it says ‘low salt’ add a bag, or for your small pool, probably only 1/4 of a bag - enough until you chlorinator is happy.

Try hard to ignore the pool store advice, they don’t recognise the relationship between FC and CYA. With a CYA of 70ppm you need to maintain a minimum of 5ppm FC, I’m happier with my pools at 6-7ppm. Stay away from powdered chlorinated products, particularly when your almost at You CYA limit.

Have a go at putting your pool details into your signature, it helps us to help better. ;)

And it you haven’t already have a read through the pool school pages.
 
Hi AUSpool, definitely looking into the CCL kit. I'm currently using the Technix for TA & Aussie Gold for pH.

Reason for the CH to move up to 427 is due to additional hardness addition. I guess I'm trying to ensure my CSI is in the -0.3 - 0.

Generally how long would you let your pool sit around the low 8's?

Re salt, I'm referring to the manufactures recommendation levels, I'll check the chlorinator tomorrow to see what it says.

I'm definitely ignoring what they have to say - keep trying to sell me ph buffer! As they report on adjusted TA as well. Don't I need to maintain a minimum FC of 3?
Thanks mate!
Sorry, do you think running the spa for more than 30min a day help cure the pebblecrete? thanks!
 
alexsmith1 said:
...

Reason for the CH to move up to 427 is due to additional hardness addition. I guess I'm trying to ensure my CSI is in the -0.3 - 0.
...
Click to expand...
I keep my pools on the low side of the CH scale. In the absence of heavy rain my CH constantly creeps up from calcium in the top up water.

alexsmith1 said:
...Generally how long would you let your pool sit around the low 8's?...
Click to expand...

Never, not that it would hurt much for a little while. What I was saying is that both my pools bounce back to 7.8 very quickly and tend to stay at 7.8 for long periods of time. A rising pH will tend to pause for a while at 8.3.


alexsmith1 said:
...
Sorry, do you think running the spa for more than 30min a day help cure the pebblecrete? thanks!
...
Click to expand...
No. Dont know. But you need run the pump long enough to manage your FC. Or you’ll soon have little green swamp to deal with.
 
Hi AusPool, thanks for the prompt reply.

1. May I ask for your general CH target? I was under the impression to aim between 350-450

2. Will you add acid when your pH creeps above 7.8? I too find my pool likes to sit on 7.8. I'm not sure if I should keep adding acid to bring it down to 7.4-7.6ish

3. Spa is 5000L and my pump turns over 250 or so litres a minute.. pump isn't a "spa" pump. I actually need to ensure it doesn't pump too much chlorine haha!

Many thanks
 
TFP’s recommended target for calcium hardness CH is 350 - 450ppm for a plaster (concrete, pebblecrete) pool with a SWCG. Be careful not to get confused, its just calcium hardness CH, not general CH. General hardness includes magnesium which is not worth chasing because its way more soluable than calcium.

I target a CH of 350ppm. Having said that one of my pools is exposed and uses lots of top up water. With ~60ppm CH in my top up water the CH and TA are constantly increasing. It’s currently at 450ppm. The other pool is a little cooler and doesn’t use as much top up water. It just tested at 325pp so Ive brought it back to 350ppm. Targeting the lower end gives me ’wriggle’ space, I think its easier to add CaCl than remove water.

Both my pools sit at a pH 7.8 and if I lower it, it will bounce back to 7.8 very quickly so I just leave it a 7.8. I occasionally dose it down to 7.2 to lower my TA as needed.
 
:p I’m not 100% sure why my pools seem to pause at 7.8. I just checked my top up water again and it was at 7.4, a lot of top up water may have a lot to do with it. But to be clear I check my pH at every minor test, (TC, pH, salt), If my pH was above normal I would dose it down to 7.6. If my TA has creeped up I’ll dose the pH down to 7.2. pH rise in non stabilised chlorinated and swg pools is a function of CO2 out gassing. It is not linear, it will move quite quickly from 7.0 to 7.5 then low as it gets above 7.6.

You can manage your pool in your absence or just leave it. If you keep records you will get an idea of your weekly acid demand and prepare two - three diluted acid doses for a friend or relative to add at intervals. Get in a pool service on a temporary basis to do the same. Or install an acid pump - unfortunately I haven’t found one that doesn’t use a pH meter for control.
 
I feel like my pool too pauses around 7.8! I generally leave it at 7.8 unless the Aussie Gold kit reports an 8.

I actually have a log book (best idea!). I generally add 2cups of acid every 3-4 days. Where as the spa needs 1/4 cup acid every second day along with some buffer.

Acid pump hey.. why are you after one with no pH meter? I suspect $$? Cheers mate!

EDIT: My top up water pH is 7.2
 
Last edited:
alexsmith1 said:
...

Acid pump hey.. why are you after one with no pH meter? I suspect $$? Cheers mate!

EDIT: My top up water pH is 7.2
Click to expand...

Simplicity. Wont need a probe port, no calibrating. Simply test, log and adjust as I would with a SWCG. Going to start a new pool build soon and am expecting a high initial acid demand.

I had previously tested my top up water at 7.2, but got 7.4 this weekend, might have to split the difference at 7.3. For interest sake a 2014-15 water quality report gives a range of results between 6.6 and 8.6 with a average at 7.5 for my area.
 

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