Questions about moving to TFPC method

[TobyB]

Hi,

I've got a 1000litre vinyl hottub which I've had for 4 years. I currently use a number of pool chemicals and test strips (although I am looking to change this).

As well as the standard chemicals, I currently use:

• Scale control (to reduce hard water)
• Clarifier
• MPS spa shock

Is my understanding correct that:

1. Using bleach/liquid chlorine I won't need to use clarifier and spa shock anymore? (and that this will be replaced by raising the FC to 12ppm whenever the CC is greater than 0.5ppm?)
2. Using the TFPC method, should I stop adding scale control? According to my water supplier the calcium hardness in my area is 270 ppm. I am worried that if I stop, the heater may get blocked with scale.
   • I've never measured calcium hardness before but I see it is a measurement on the PoolMath app. My hot tub liner is vinyl, so I understand calcium hardness isn't as important.
   • My previous hot tub heater failed after 2 years and was blocked with scale. At the time I wasn't so good at adding the scale control on a weekly basis as suggested by the hot tub supplier as the water generally looked clear, the PH, TA and chlorine were balanced (according to the test strips which I now know through this forum aren't accurate).
   • Is this something I will need to measure if using water from the same source or would I be able to just use the figure my water supplier has provided?
3. I have never tested the water for metals but as I will be cutting out the spa shock and clarifier, is this something I should start monitoring in case they build up over time?
4. Is there anything else I should be monitoring for a hot tub apart from PH, TA, Chlorine (CC, FC, TC) and CYA?

Thank you in advance for your help and I apologise for the many questions.

 

[Methuselah]

If you've been using it and it's been clear, no skin rashes or chlorine smells over 4 years, aside from heater issues you must be doing something right.

How often do you change water, clean filter, how much use (bather-hours a week), and how long does the filter cycle run (is there a circulation pump)?

If you have a scale problem saturation index would be a good search term. As for metals it is not typically an ussue if your fill water is municipal, but having your source water tested couldn't hurt.

 

[TobyB]

Hi,

Thanks for the help and sorry for the slow reply. I was reading about the saturation index and other chemicals and ended up down a bit of a rabbit hole. I wanted to get my bearings a bit more with the TFPC method before I replied.

Previously I was generally changing water about every 3 months (although after the heater failed I have had issues with getting the water right and being able to use the hot tub). Since I've had a new heater as the hot tub was out of action for a few weeks I had multiple issues with the water quality and was slightly guessing what was wrong, this involved purging the pipes, shocking and continuously checking chemicals. I also had some leaks and eventually had to replace the liner as the liner had come away near an air jet hole.
Once I would get the water clear again / repair the tub I would find if I went away for a few days without monitoring it, it would be bad again and I would be back to guessing.

I used to use the hot tub about 4-5 days a week although since the heater failed and the other problems it has often been 1 day if I'm lucky. The filter cycle runs 24/7 and I would clean the filter every 1-2 weeks.

I have been testing using the TFPC method for about a month now and the water has been very clear and I've got a proper test kit which has shown me how wrong some of the test strip readings were. After getting used to the method a bit more I am feeling more confident and won't be using clarifier, shock or scale control and am monitoring the CSI index as part of my tests. I may eventually add borates into the mix if I have issues with my alkalinity creeping up although it's been ok so far.

As part of my tests everything has been within range apart from the CYA s I was still waiting for liquid chlorine. I also let the FC drop slightly lower the last couple days while I was waiting for this to arrive as I didn't want to add to much more CYA. I added the liquid chlorine today and was a bit surprised.

My CYA is 71 and my FC was 1.61 and my CC was 0.74 . I added 45ml of 15% bleach as suggested by poolmath and when I checked 2 hours later my FC is 2.24 and my CC is 0.

I was a bit surprised by this as I was aiming for a FC of 7. I'm not sure if having a CC of 0.74 would use up 4.76 FC or if the bleach I bought could maybe be bad. Anyway I'll raise another thread for this so I don't go too off topic.

Thanks again for the help

 

[JoeSelf]

I would keep it all in here. If you CYA is 70 you need to raise your CYA per the chart.

Bleach check the date code. Usually is the year XX, than sequential day YYY. XXYYY - 23135 is the 135 day of 2023.

 

[TobyB]

Thanks, so I understood my CYA was slightly high and so I aimed to raise my FC to 7 as suggested by the poolmath app for my measurements.

I checked the label and it doesn't seem to follow that format but I assume it was produced on 23/05/2023 based on the batch number which I've attached.

I had unfortunately already started the new thread before you replied. I thought it may have been better as it's a bit more specific to my bleach query. It's on this link: Liquid bleach didn't increase FC by what I was expecting but I don't think I should remove it now as I see I've already had a reply.

Thanks

 

[Methuselah]

CYA is too high, and @JoeSelf meant raise FC commensurate with that CYA level.

Yes, you used up the CHL bringing down the CC level.

The other thread is more aptly titled for continuance. Whew, all those $2.00 words wore me out