CYA - could it really have doubled in less than 2 weeks?

[PoolCleanerMom]

... or was the in-store test *that* far off?
on 8/27/09 I took a water sample to the pool store and got good results:
FC 5
pH 7.4
TA 120
CH 200
CYA 50

I still had tablets in a floating dispenser at the time and have switched to liquid chlorine. I got my K-2006 last Friday and have been getting CYA results of 100?!
today's results:
FC 1 (added more bleach this morning to boost it back up)
pH 7.3
TA 180
CH 230
CYA 100

I know my CYA is higher than it ought to be b/c I'm adding chlorine daily (example: on 9/5/09 I added 1 gallon of 10% bleach - about an hour after the addition my FC was up to 5, by the following morning it was down to 2.5 and by the following afternoon it was hardly detectable... I've also got a bit of a mustard algae issue that I'm keeping in check by brushing every other day and adding more chlorine towards the minimum FC although not up to the 20+ ppm shock levels on the CYA/Chlorine chart. But is it really possible that the levels could have doubled in less than a month, or could the pool store result have been artificially low for some reason?

 

[no-mas]

The pool store is inconsistent because often you'll have different people testing, and just as often, they have little to no understanding of what they are doing and why they are doing it. This is the single best reason to purchase yourself a good test kit, read up on BBB in pool school and test and treat the water yourself. Knowlegde is power, and YOU will be in control of your pool.

 

[PoolCleanerMom]

OK, so then if I assume that the results I'm getting with the K-2006 kit are a more accurate measure of CYA than the pool store result, I'm wondering what method of dealing with it will be most practical. Water conservation measures are in effect here so the most effective method of doing a partial drain and refill of a 17000 gallon pool is not my first choice, given that the water district has allotted us about 30K gallons total for our whole household's current 60-day billing cycle. So this morning I did some hand-watering of the garden with pool water before I boosted the FC level back up to around 9 (we have a submersible electric pump that I can connect to a garden hose) and then topping it back up, but of course that's just drops in the proverbial bucket.)
So, do I just try to slowly drain and refill incrementally with the 'garden method' and hope for good rainfall this winter to minimize the amount of refilling I need to do directly from the tap, while trying to keep my FC readings around 7-10 to keep the algae at bay?

 

[Butterfly]

I agree with no-mas that the pool store test is off.

If you are not confident reading the CYA test, try this link from Taylor Technologies for the visual test:
http://www.taylortechnologies.com/Chemi ... ntentID=44

Trust YOUR test w/the Taylor 2006

Again, I recommend, if at all possible, to lower your CYA to at least 70 so that you have a workable CYA #.

Maintain FC based on your CYA level from the Chlorine/CYA Chart. (Link in my sig & Pool School)

 

[Butterfly]

Oops, you posted while I was.....

You do have a dilemma.

So, do I just try to slowly drain and refill incrementally with the 'garden method' and hope for good rainfall this winter to minimize the amount of refilling I need to do directly from the tap, while trying to keep my FC readings around 7-10 to keep the algae at bay?

This may be your only option?....but w/CYA of 100 maintain FC more like 7 to 12 or 14-ish.
How does your water look now?

What is your CC?

 

[PoolCleanerMom]

How does your water look now?

What is your CC?

It looks pretty good - a little opalescent from dead algae and color is a little off from blue
test at about 9 pm tonight showed FC of 11, CC of < 1, will take another reading tomorrow morning and post back.

 

[PaulR]

Let's double-check that your own CYA test is reasonable.
- You want to do the test in daylight with your back to the sun, so pretty good light but not directly on the view tube.
- When you think the black dot has disappeared, wiggle the tube a little bit. Eyes are good at catching motion, and sometimes you'll notice the black dot again if it's moving.
- Do it 2-3 times and see if you get consistent results (pour the stuff back into the mixing bottle; no need to burn through all your reagent doing just one test).
- Pour the stuff back into the mixing bottle and get someone else to try the test.

If you are consistently getting 100+ in these conditions, then dilute the (already mixed) sample 50/50 with tap water, shake it up, and try again; double the result. This will tell you whether it's more like 120 or 180. (We had one case recently where it was actually up around 400. )

Now, about draining and refilling under drought restrictions. Your 30k gallon allocation (EBMUD, right?) is 40 units of 100 cu ft each. Your 17k gallon pool holds around 22 units. With a surface area of 15x30 or 450 sq ft, each 2.5" you drain and refill is not quite one unit. SO, if you drain and refill around 3", you've replaced about 5% of your water and consumed just over one unit of your 40 unit allocation.

You'll have to decide how much of your allocation you can use for this purpose, but I expect you'll have what we here would consider excessive CYA well into the winter. It's not the end of the world, it's just not what our recommendations and instinctive responses are tuned for.

Final note: If you drain, Bay Area water districts generally require that you drain into the sewer (not the storm drain on the street, and not onto the ground). Backwashing (or watering the yard with pool water ) doesn't count as "draining" it's not enough water to matter, but once you start talking an inch or more then you'll need to start following the stricter rules.

--paulr

 

[heikejohn]

How do the plants handle the high CL level with the watering?

 

[frustratedpoolmom]

Back when I was dealing with high CYA and I had to do a series of partial drains and refills, the grass and trees near my pool were unaffected by the water chems.

 

[frustratedpoolmom]

PCM, I've been thinking about your issue and was wondering something - can you check your past bills to see your average monthly usage? I average about 6,000 gallons a month for a family of four (with normal usage, IMO) and I can't help but wonder if even with doing a couple partial drains, that you won't hit your max limit - you may come close but I doubt you'd reach it....

I'm not suggesting you do half your pool all at once but if you did a foot or so a couple of times over the next 2 months you could lower the CYA level to a manageable number - I think you can mangage this by conserving water in other areas of the home (assuming your montly usage is around mine...).

 

[PoolCleanerMom]

PCM, I've been thinking about your issue and was wondering something - can you check your past bills to see your average monthly usage? I average about 6,000 gallons a month for a family of four (with normal usage, IMO) and I can't help but wonder if even with doing a couple partial drains, that you won't hit your max limit - you may come close but I doubt you'd reach it....

Our water usage during the summer is predominantly irrigation - during the winter our family of four averages less than 100 gallons a day (compared to 500 gallons/day in summer time) so our in-house conservation is pretty well maxed out. That's why we think diverting the pool water to irrigation is the only way we can replace our pool water without incurring the wrath of our water district.

FPM: How high a CC level did you have when you did your partial drains/refills? is 10ppm a bit much for lawns and shrubs? (I did the past couple irrigations before I bumped the FC up)

This morning's FC reading was 7.5, CC 0.5 so I've dropped 3.5 ppm in the past 12 hours. If I keep bumping the FC up to around 10+ for the next few days (I'm assuming the chlorine burn rate is b/c I've still got some mustard algae), will my FC level stabilize so I won't be adding a gallon or more of bleach every day?

Off to re-check my CYA levels.... Thanks everyone for your help. Hopefully I'll soon be able to graduate from "BBF" (Bleach, brush, and filter) to BBB :-D

 

[no-mas]

Wish I could send some of the rains we had this summer your way - I don't think we've run our irrigation system since March.

I'm happy to see you trust yourself and your testing ability, though. The more you do so, the better your understanding and predicitability of your own pool. You'll be at BBB instead of BBF before you know it. :-D

 

[PoolCleanerMom]

If you are consistently getting 100+ in these conditions, then dilute the (already mixed) sample 50/50 with tap water, shake it up, and try again; double the result. This will tell you whether it's more like 120 or 180. (We had one case recently where it was actually up around 400. )

Now, about draining and refilling under drought restrictions. Your 30k gallon allocation (EBMUD, right?) is 40 units of 100 cu ft each. Your 17k gallon pool holds around 22 units. With a surface area of 15x30 or 450 sq ft, each 2.5" you drain and refill is not quite one unit. SO, if you drain and refill around 3", you've replaced about 5% of your water and consumed just over one unit of your 40 unit allocation.

Thanks for the tips and water replacement calculations, PaulR - I did a 50/50 dilution and it looks like my CYA is about 120 . So it looks like it'll be a long slow drain a little/refill a little process... another reason to hope for good rainfall this winter

 

[frustratedpoolmom]

FPM: How high a CC level did you have when you did your partial drains/refills? is 10ppm a bit much for lawns and shrubs? (I did the past couple irrigations before I bumped the FC up)

This morning's FC reading was 7.5, CC 0.5 so I've dropped 3.5 ppm in the past 12 hours. If I keep bumping the FC up to around 10+ for the next few days (I'm assuming the chlorine burn rate is b/c I've still got some mustard algae), will my FC level stabilize so I won't be adding a gallon or more of bleach every day?

It varied. I've drained water that has been as high as shock level and noticed no ill effects.

Do you cover with a solar blanket during the day when the pool is not in use? This helps to cut down on UV loss. You should see the levels stabilize, but every pool is different in it's usage. I lose less than 1ppm in my pool when the solar cover is on, but that's well below the average pool.

Confirm your overnight loss tonight and then once you get your CYA down you can shock the pool and hopefully your chlorine usage will be less.

 

[fordsbyjay]

Is there any way you could have water delivered? Where I am from they have water stations for acreage people with cisterns and they don't ever seem to be effected by water bans.

 

[PaulR]

Yeah, we just got our water bill.... the irrigation really chews it up. But if you're just watering the lawn and the bushes, using pool water would be okay. It would just be a pain to do it on a large scale, or very often.
--paulr