Newbie having problem with high Ph and TA in SPA

[dondaviduk]

Hi all,
I just bought an inflatable hot tub/spa a few days ago, and after its initial fill and chlorine shock dose, the following day I carried out a dip test (using ClearWater strips). Chlorine levels had dropped down to 5 but the Ph and TA levels were at maximum. I added 9g of Ph minus and waited the advised 4hrs, upon re-test i found all readings to be exactly the same. I left it overnight and tested it to be still high this morning (chlorine looks to have dropped off a little). I then added another 9g of Ph minus and 4hrs later I'm still seeing the same Ph and TA levels. My main concern is the continual adding of chemicals when I am so inexperienced with it all. A point of note is that I live in the UK in a hard water area (which I have googled to be high Ph in itself).

Could anyone leave any advice or tips? It has been mentioned to me to remove some water and re-fill from the hosepipe, and even adding white vinegar?

Thanks in advance
David

 

[jseyfert3]

Hey, welcome! This might get a bit long, please bear with me!

Test kits: You need a better one. Recommended models are they Taylor kits or ones from TFTestkits.net. You're looking for the FAS-DPD chlorine test. These test kits use a color-changing drop based test, and are much more accurate and have a much higher range than test strips. It's difficult to properly care for a pool/spa without one of these kits. Not sure how difficult it would be to get in the UK but you really should try to get one.

Test results & equipment: To best assist you, we need you to list your latest water test results & your equipment. Typically it's easier to list your equipment in your signature so you don't have to list that every time you start a thread. See my signature as one example.

Setup Guide: To get your water balanced, there's a fairly detailed thread that walks you though this, and is the starting place for anyone using chlorine in their spa: How do I use Chlorine in my Spa (or pool)?)

Some notes on your situation: Without knowing your exact water specs, I'll give my own spa/water as an example. My spa is ~290 gallons (1100 liters), and my water has a TA of 275 ppm. To reduce this to desired levels, which is approximately 50 ppm for a spa, I had to add acid, lots of acid. I used Muriatic Acid (Hydrochloric acid) instead of sodium bisulfate (dry acid or pH down), as dry acid will eat out metal components such as your heater eventually. And I needed to add a large amount of acid. Using 32% HCL, I had to add roughly 19 oz (560 mL) total to drop my TA to around the 40-50 ppm mark. Not all at once, of course, but a few oz at a time, aerating in between additions. This is laid out in the instructional thread linked above.

You said you added 9 g of pH down. According to PoolMath, 9 g of pH down will lower pH by 0.18 and will lower TA by 3.2 ppm. That's nothing. If your TA is anywhere near as high as mine, you'd need well over half a kg of dry acid (added over time) to drop the TA to normal levels. According to PoolMath, 500 g of dry acid will lower TA by 177 ppm. Of course don't add it all at once, you'll tank the pH and cause massive damage to any metal parts within the spa, it's just to give you an idea of how little effect that tiny amount has.

My suggestions: Try and get a recommended test kit, it really is needed. See if muriatic acid (HCL) is available in the UK to use instead of dry acid (pH down), here in the US you can buy it at any hardware store. Read and follow the linked thread for using chlorine in your spa. Ask here if you have questions along the way.

 

[ajw22]

Test strips are notoriously inaccurate. You need a simple drop test kit for PH and CL. A Taylor K-1000 Basic OTO Test Kit would do. Or you can get a more sophisticated test kit like the Taylor K-2006. I understand the Taylor test kits are expensive in Europe. See Test kits in the UK

I would not go chasing strip results adding chemicals until you had a reliable test kit.

Don't worry about TA unless it gets very low. Manage your PH and CL.