Low calcium hardness in vinyl pool ok?

[waste]

Hi Shaggy;

Watermom asked me to take a look at your post -- she's right, it reads like you've been drinking a lot of the pool industry koolade, whether you are in the biz or not.

Several important points:

1. Low pH will damage copper pool heaters; low hardness does not.
2. Hardness -- at ANY level -- is only an issue in a 'plastic' pool (PVC pipes, vinyl liner, polymer pump) if it's HIGH. A hardness of 10 is fine in a plastic pool.

In general, the whole saturation index thing the pool industry has wasted so much paper on, doesn't apply to most pools. It's significant in PLASTER (cement & marble dust) pools, but overblown or inapplicable almost everywhere else. The entire situation is a mess.

If you are a pool owner, the answer is don't worry about it much unless it's too high, or unless you have a plaster pool.

If you are in the pool biz, this is a discussion that belongs in the China Shop.

Best wishes,

PoolDoc

Speaking as someone in the business - GREAT ANSWER! (but I wouldn't know that, if I hadn't joined this site)

[chem geek]

There's a lot of discussion among the experts on whether calcium carbonate saturation helps to prevent metal corrosion and you can read just one such discussion here:

http://corrosion-doctors.org/Cooling...orrosivity.htm

The bottom line is that it is pH that is a critical factor in corrosion and next would be a low TA since that would allow for a low pH locally when there is no water flow. The presence of chlorides, sulfates and generally the conductivity of the water are also important. Of course, one must have an oxidizer in the water as well such as dissolved oxygen or, of course, in pools we have chlorine. Calcium carbonate saturation is iffy at best since getting a consistent protective patina is quite difficult to achieve. If calcium directly interfered with the corrosion process, then that would be different, but there is no evidence that this is the case.

Many people have copper plumbing in their homes and have either chlorine or monochoramine in their water systems yet the water is often very low in CH (50 ppm or lower). Water districts often add some corrosion inhibitors, but they don't saturate the water with calcium carbonate. Also, there is no CYA in tap water so any chlorine is far, far higher in active concentration than found in pools. Pools with an FC that is at or above the minimum in Ben's Best Guess CYA chart (an FC that is 7.5% of the CYA level) are equivalent in active chlorine concentration to water with only 0.06 ppm FC with no CYA.

[CarlD]

I would add that if hardness were good for plumbing we wouldn't have so many water softeners!

Everyone's left out that excessive hardness causes scaling and that's not much better than corrosion. Anything that uses a lot of water, from a coffee maker to your faucets are victims of scaling.

I think Richard's message (and mine would be) that proper pool chemistry maintenance is all you need--so skip the calcium in vinyl pools!

[expertmagician]

I know this is a very old topic...and I am new to this forum...But, I am a new pool owner of a semi-inground pool with a Hayward Gas Heater (150,000 BTU).

I do not knnow what the coils are made of...But, Hayward said that calcium should be at 200ppm - 400pmm. That sounded high and the guy I spoke too sounded new...reading scripts. (Must be sumemr help becasue the people I spoke to in the winter during my research were very knowledgeable).

In either case, I was wondering how to test for calcium and if I should keep it as high as 200pmm in my Vinyl semi-inground pool ?

Thoughts ?

Hopefully, I will turn my pool on this weekend after the electrician comes...this is the first pool I owned othet than a 10 foot round Intex.

[Watermom]

Welcome to the forum. Please see Ben's post (post #7) in this thread. He addresses this issue.

[maryberrye]

Since I have a vinyl pool, I've taken Carl's advice and never bothered with the CH test. I am curious though what Ben's idea of a too high calcium reading is? We live in an area with very hard water - 469 ppm. Is this too high?

Thanks,
Mary

16k IG vinyl
FC 4.0
CC 0
PH 7.5
CYA 29
ALK 240 (working on it now)
temp 80

[CarlD]

If your CH is close to 500ppm and your T/A is 240ppm, you are in danger of your pool going very milky. It will be safe, but not too pretty.

Get your T/A down to at least 100, or even 80 and you should be OK. But don't add anything with calcium, ever!

[aylad]

The problem with high calcium in a vinyl pool is that it can make the water very milky, especially after being shocked. In an area where your fill water is very high in calcium, then you need to try to keep your alk and pH on the lower ends of the normal range, especially if your water looks cloudy and won't clear with shocking.

Janet

Edit: Carl beat me to it this time!

[Watermom]

No cal-hypo for you! By the way -- maryberrye --- welcome back to the forum for another swim season!

[maryberrye]

I've never been able to get my TA down below 180. I am faithfully adding small amounts of muriatic acid (diluted in a bucket of water before it goes into the pool) to lower the PH to 7.0 then bubbling the heck out of it with the air compressor bubbler my husband juryrigged for me on Saturday. All the while keeping my pump running. The water was very milky yesterday but I shocked it, and it's clear(ish) now. At 180 TA we get very clear water if everything else is properly maintained. I doubt if I will ever get my TA as low as 80-100, I'm not that patient. And, not to worry, I have avoided adding anything to do with calcium for the last five years, since you all have reaffirmed it's not necessary, I can't imagine wanting to start now

Thanks all for the welcome backs!

Mary