Chlorine, CYA, and PH levels with a heat pump

[GalenL]

I am about to install a Crosswind 65-I heat pump.

The manual recommends FC in the range of 2-3 ppm, with a stern warning in bold in that FC MUST NOT EXCEED 5 PPM (see screenshot below):


I use a SWG. TFP recommends I bring my CYA up to 70 or 80, and target an FC range of 5-10 or 6-11. This exceeds the maximum per the installation manual by a considerable margin. Is this a reason for me to keep my CYA lower, along the lines of that for a regular chlorine pool (30-50)? Right now, my CYA is at 40, andI've been hesitant to raise it out of concern for the heat pump. I would also note that I use an opaque automatic cover, which prevents the breakdown of chlorine from the sun to some extent. However, I'm not sure what is behind the recommendation for using so much more CYA in SWG pools?

Separately, the manuals recommended PH is different from the TFP App's "Ideal Range" of 7.6-7.8. Does anyone have insight into this difference, and whether I should go with the TFP or Crosswind Manual's recommendations?

Thanks!

Galen

 

[Newdude]

Does anyone have insight into this difference, and whether I should go with the TFP or Crosswind Manual's recommendations?

That's like asking Ford if they think you should drive a Chevy or a Ford.

Manufacturers follow generic industry levels that haven't been updated since the 80s or 90s. We evolved with the times.

One big difference is the industry believing that there is no CYA / FC relationship. 5 FC with 0 CYA would in fact be very harsh and they treat 5 FC the same regardless of CYA levels. All of our recommendations are safe for swimmers, finishes and equipment.

Have a read :
FC/CYA Levels
Pool Care Basics

 

[GalenL]

OK, that's fair.

So my real question is, can I follow the TFP CYA/Chlorine guidelines without damaging my heat pump, notwithstanding what the Crosswind Manual says?

Same question for PH: Will keeping PH at 7.6-7.8 damage the heat pump?

EDIT: I guess your answer to both questions is yes, I can follow TFP's recommendations without fear of damaging the heat pump?

I'd also love to better understand the reasoning behind TFP's recommendations. What problems if any am I likely to experience if I keep my CYA at 30-40, FC at 3-5, and PH at 7.2-7.3?

 

[mgtfp]

The recommended TFP values will not damage your heat pump, but that's not the point here.

If you have any issues and lodge a warranty claim for whatever reason, they will use any excuse to weasel out of their responsibilities - that's why they've put these requirements up in the first place. Unfortunately, what's "legal" is not always ethical. Quite the contrary actually, in many cases.

A decision that you have to make for yourself.

Probably wouldn't hurt to collect a few pool store test results that show your water being in their range. That's probably the only "evidence" they'd accept in the first place.

The range that they are demanding is a range that they have verified to be OK for their heat pump. That doesn't mean that it's the only range, but they don't accept responsibility for other ranges. They also don't really care that their range is a pain to maintain from a pool owner's point of view. Not sure if it's a coincidence that this range is a licence to print money for any pool store...

Unfortunately that's the work of lawyers, marketing and business people, not scientists.

 

[ajw22]

What problems if any am I likely to experience if I keep my CYA at 30-40, FC at 3-5, and PH at 7.2-7.3?

You can work hard trying to maintain that. It will be more work then TFP What Are My Ideal Pool Levels?

Note that the Crosswinds water chemistry table does not even list CYA. They do not recognize the difference between active chlorine levels and reserve chlorine levels once you add CYA. Read CYA Chlorine Relationship - Further Reading

It is your pool, your equipment, and your choice of how you want to operate it.

 

[GalenL]

Thanks all, this was very helpful!

 

[Newdude]

I'd also love to better understand the reasoning behind TFP's recommendations

Start with clicking/reading the links I listed above (blue words). Ask away from there and we'll help fill in any blanks.

 

[GalenL]

Start with clicking/reading the links I listed above (blue words). Ask away from there and we'll help fill in any blanks.

Thanks! I was up to date on the basic primers in the pool school, but I spent some more times digging through the forum and found this discussion that helped me understand what's behind the recommendation to maintain SWG pools at much higher CYA levels: CYA in salt vs non-salt pools

 

[Newdude]

found this discussion

Awesome. !!!

Also check the Wiki towards the bottom of any forum page, or in the left sidebar.

Many topics are discussed into the nitty gritty there. Peruse anything relevant to you in your free time.

 

[reggiehammond]

View attachment 573594
I'd also love to better understand the reasoning behind TFP's recommendations. What problems if any am I likely to experience if I keep my CYA at 30-40, FC at 3-5, and PH at 7.2-7.3?

Just to answer this specific question. You can 100% be within TFP recommendations with the above values and experience no issues. Your FC would be above the min for the FC/CYA relationship.

TFP recommends higher CYA for SWCG pools because it lessens the FC demand, lengthening the life of the SWCG (they're consumable.) Other values that are recommended in Pool Care Basics are based around trying to make pool care as easy as possible. Managing pH to .1-.2 resolution is possible, but will be a lot more work when the evidence is that it's not worth it.

With a SWCG, you are freed from a lot of the daily need to care for the pool chemical levels. But the trade off is that you do need to manage CSI levels to avoid scaling at the SWCG.

 

[GalenL]

Just to answer this specific question. You can 100% be within TFP recommendations with the above values and experience no issues. Your FC would be above the min for the FC/CYA relationship.
it.

Thanks! I wonder if the downsides of a maintaining lower cya (and corresponding FC) levels might be lessened for me by the fact that I use an opaque auto cover most days. I seem to be stable at 4.5 FC running my swg for 6.5 hours a day at 15%. Hard for me to imagine more cya taking me much lower than that.

Admittedly my FC dropped last time we used the pool in all afternoon in full sun, so I’ll need to watch my FC while in use. I’ve since upped my CYA from 30 to 50, so I’ll see how it goes this weekend.

I did check the heat pump warranty, and it didn’t specifically mention chlorine as something that would void warranty, whereas it did mention low PH as something that would. So I’m feeling better about following TFP recommendations.

Still, for things like cya and calcium carbonate I’m upping my levels slowly as I learn my pool, that are easier to add than remove.

Thanks again all!

 

[Newdude]

the fact that I use an opaque auto cover most days.

You effectively have 2 pools.

98% of the time the covered pool behaves more like an indoor pool.

If you're using the pool, then it will swing like a regular outdoor pool. In the evening there will be little loss. If it's a lunchtime swim or full afternoon party, you'll see much more loss.

Said loss can be mitigated with more CYA, or simply paying attention to the FC at the time and planning ahead.