Pressure issues

[goosemonkey]

Hi everyone,

I've owned this house with this pool for about 10 years now. Sadly, I've really grown to hate the pool: it's like having a toddler; you can't leave it alone very long or it will get into trouble. That being said, we've had our share of issues: underground pipe leaks, pump dying, heater dead, spa tiles falling off...

Anyway, for the past two seasons, I've been having a lot of trouble with keeping my pressure down. Even after I completely pull the DE filter apart and clean the grids, I can only get the filter to run for 8 hours 2 days in a row before the pressure jumps up to 30+ psi. For awhile I thought it was a mechanical problem, but now after finding this forum, I'm wondering if it's a chemical problem.

I bought the big kit and here are the latest numbers:

pH: 7.5
FC: 10.5
CC: 1
T/A: 90
CH: 410
CYA: 100+

The water is cloudy and when I pull apart the filter to clean it, there's definitely a green to it. I also have trouble with calcium build up, particularly at the waterfall from the spa into the pool.

Any initial thoughts based on this?

Thanks!

 

[superman0604]

Good chance your CYA is higher than 100, trying diluting it with 50% pool water and 50% tap water. This could be allowing algae to start growing which might be the cloudiness.

 

[duraleigh]

Hey, Goose,

Welcome to the forum. :lol: Yeah, you have some chemistry issues. You are almost surely killing algae in your pool and it is being pulled into your filter where it is quickly clogging your filter........your filter is doing it's job, you just have to much gunk that it is trying to filter out. Once the filter gets full, your psi rises and your flow will slow.

While your primary issue is inadequate chlorine, the root cause of that is your CYA is too high. read "The ABC's of Pool Water Chemistry" up in Pool School. Then, I would suggest you plan to drain about 50% of your pool water to get your CYA to a manageable level.

Once that drain/refill is accomplished, it will be pretty easy to shock the pool correctly and get your water crystal clear.

Please test the CH of your Fill water and report that before you start.

 

[BadOleRoss]

Hmmmm, 2 replies before I got done typing.....gonna post it anyway.

Welcome to TFP. I think you answer the question yourself when you posted. You said "The water is cloudy and when I pull apart the filter to clean it, there's definitely a green to it. I also have trouble with calcium build up, particularly at the waterfall from the spa into the pool". I don't think you have ever gotten the pool clean. There is algae and other particles in the water that the filter is attempting to filter out but it is becoming overwhelmed. CC of 1 indicates you are in need of shocking the pool but with a CYA of over 100 you really need to do a partial water change of about 50% to get your CYA in the 50ppm range. The scary part about a CYA of over 100 is that test kits do not accurately measure CYA over 100.....so you might be looking at a CYA level well over 100.

 

[goosemonkey]

Thanks, everyone. It's encouraging to hear I'm on the right track! Cool.

50% water replacement...15,000 gallons sounds like a lot of water. I'll call around and see what that will cost and to see if they can give me the CH before they deliver.

 

[goosemonkey]

Okay, so I pumped about half my water out and had 12,000 gallons of water trucked in and the pool filled. The new values:

Cl 3
Br 6
pH 7.5
FC 4
CC 0.5
TC 4.5
T/A 70
CH 300
CYA 110

I'm worried because the CYA does not seem to have come down much. My test kit has me fill up the mixture in a tube and add until I can't see the black dot at the bottom. It seems a bit subjective to me.

At the same time the pools is turning green.

Thoughts? Advice?

Thank you!!!

--the goose

 

[spidey07]

If your CYA is 100+ your free chlorine is way too low to do it's job (see pool school cya/FC chart) and you will get algae (green pool). Shocking also becomes incredibly difficult because of how much bleach you need. The test isn't reliable past 110 or so, experts please correct me on this. Recommended to use 50% pool water and 50% tap and then repeat the test with this sample, then multiply by 2 to get real CYA level. If you truly replaced 50% of the water in your pool, then your CYA went down 50%.

More likely your CYA was much higher than you thought, giving you the problems you see. Keep following advice here and in pool school, you will get it nailed down. But your water needs work with CYA that high, more replacement.

Get that in line and you can go through the shock process.

 

[jblizzle]

yup. Spidey07 ... gave good advice.

Posted from my Droid with Tapatalk ... sorry if my response is short

 

[goosemonkey]

Thanks, spidey07.

I did as you suggested and re-ran the CYA test with half pool water and half tap water. I'd put CYA between 110 and 120.

I paid $380 for 12,000 of water and it didn't seem to make much of a difference to CYA. If I understand your reasoning, you're suggesting that my CYA before the water replacement was much higher than the 110 I measured. Therefore I didn't replace enough water. Right?

To fix it, the only solution is to do another replacement. Correct?

This is getting quite expensive at this rate. How do I ensure that I replace enough of the water to fix it? If I do another 12,000 gallons, am I pretty well assured that I'll be in a good range? Should I do 18,000 gallons? I've been told that if I get the water too low that I'll be in danger of introducing cracks in the pool because of the way the pool settles over time under the weight of all the water. Should I be concerned with that? Also, is CYA heavy? I mean is there more of it deeper in the pool? If so, I suppose I could pump out from the bottom of the deep end. Or is CYA fully dissolved in the water and therefore fairly even throughout the water. (I should have paid more attention in chemistry class...)

If you think there's a cheaper way to fix this, please let me know!

Thanks again for all the help!

 

[Richard320]

No, there ain't no easier cheaper way.

The good news is, you now have the Cadillac of test kits and you have knowledge. So once the CYA is adjusted to a reasonable number you'll be able to get the water balanced and keep it that way. A week, no more than two, and your water will be crystalline.

Don't kick yourself too hard then that you didn't get a kit and find this place years ago.

 

[goosemonkey]

Thanks, Richard320. So, what do you think, go for 12,000 gallons or 18,000 (3 truckloads)?

 

[Richard320]

Thanks, Richard320. So, what do you think, go for 12,000 gallons or 18,000 (3 truckloads)?

How confident are you of that CYA reading now?

How green/cloudy is the pool? If you're going to need the shock process, you might as well get CYA down to the 30 range, it uses less bleach. If the water is mostly clear, you can do it at 50-60.

You also need to consider the risk of floating the pool if it gets too empty - the underground water will lift it and wreck the plumbing.

 

[UnderWaterVanya]

Assume current CYA is 115 let's say.

30k - 12k = 18k unchanged.
18/30 = 60%
115 / 60% = 191 starting CYA

If you change another 12K:
115 * 60% = 69 CYA

If you change 18K:
30 - 18 = 12
12/30 = 0.4
115 * 0.4 = 46

I don't think you have a salt water chlorine generator (swgc) so the 46 CYA is much better.

Remember that when you do this you will need to avoid using any puck / tablet type chlorine as well as powdered chlorine. Liquid chlorine is the only option outside of a swgc to avoid dumping more CYA into the pool when you add chlorine.


Richards warning about floating the pool is important. Do you know the ground water level? Annapolis would be an area I would expect to have a fairly high water table. You may not be safe changing 18k at a time and may have to do two more 12k changes rather than 1 18k.

If you did two more 12k changes you should end up with:
69 * 0.6 = 41 CYA.

 

[UnderWaterVanya]

I just looked and while there is no direct data available on the source I found the information seems to suggest that the area is under a drought condition and water table levels are likely lower than normal at this time. If you are considering doing > 12K at a time - you should check with the local resources to find out ground water levels before proceeding but the drought could be your friend in this case.

Futher reading:
http://md.water.usgs.gov/groundwater/we ... /counties/

 

[goosemonkey]

Thank you all for the great information. I'm draining now, and getting close to where I was the last time.

If I did know the exact water table depth, how does that translate into knowing how much water I can remove?

We are not far from the Chesapeake Bay. Would that affect it too?

The pool is 24 years old and has had plumbing issues in other areas. We busted up a portion of the deck two years ago because the flexible PVR used had developed a leak near one of the skimmers. Ultimately, we removed the flexible PVC from underneath both skimmers. As much as I hate to spend more $, I'd much rather spend another $190 on another 6,000 gal. of water vs. dealing with anymore plumbing or decking issues. Those are expensive!

Thanks, again.

 

[goosemonkey]

Oh, also, it is very green now. Probably a strong vote for doing two 12,000 gal. changes.

 

[marty]

I read on this fourm, that if you drain pool to lawn or garden you can get some kind of credit towards water bill, couldn't hurt to call them and ask...

also, where whould all that cya come from to many pucks or maybe PG adding to much grainular?

 

[goosemonkey]

Woo hoo! Replaced ~12,500 gal. of the pool water yesterday and the CYA reading is 65 today. Is the consensus that I now have room to work with to get the algae gone? According to Pool School, it looks like 30-80 for outdoor pools should work.

 

[UnderWaterVanya]

Woo hoo! Replaced ~12,500 gal. of the pool water yesterday and the CYA reading is 65 today. Is the consensus that I now have room to work with to get the algae gone? According to Pool School, it looks like 30-80 for outdoor pools should work.

Looks like my prediction of 69 was not far off. You can make that work but shocking is harder at 65 than at 40. If you compare the two you will see that 65 cya = shock of ~ 26ppm while 40 cya = 16 ppm. The difference in cost may be offset by the cost of water change.

 

[ping]

With your CYA at 65 it is managable but it is on the high side. You definitely need to use liquid chlorine from now on unless you have a SWG. Read up on how to properly shock your pool in Pool School, pool-school/shocking_your_pool.