New Pool Owner - 1 Month In

[ASteiny]

Hi guys,

I am a new Home / Pool owner and have found TFP to be a great resource so far! I have experience in anylitical chemistry and chemical engineering, and as such I've found managing my pool to be somewhat entertaining and not overly daunting, but I am still a novice to pool chemistry and systems.

My pool is plaster, "L-shaped", includes a spa, and is approx 15,000 gallons, FW. The pool has two fixed speed pumps, one for a water feature and one for the filter system. Filtration is a 60 sq. ft DE, which I recently back-washed. The back-wash exit is piped from the filter immediately below ground with a sight glass - my assumption is it is ran directly to a drain. The pool is fresh water, but has a non-functioning SWG installed as well as a liquid chlorinator.

Chemistry wise, I am using a TF-100 test kit, Ive been recording 7.7 pH, 120 TA, 360 CH, 0 BOR (although am planning to convert to borates after I get my TA and pH down . The big issue I have is that my CYA is in the 180 range (as such I've been maintaining FC around 15+, and immedately stopped using trichlor upon closing on the house). I have seen as much as 1 CC usually only when the pool has been used.

My intention is to get my pool in line with the TFP method, but I would greatly appreciate the opinions of some of the experts her, and I've done some searching of the Forum without much luck to find anything on this topic...

With my CYA so high, is it practical to martian the pool where its at using liquid chlorine only and let it drift down over time via rain and splash-out?

If I need to replace some of the water in my pool, what is the most efficient way to do this? Some have suggested to me that CYA floats, so perhaps could I brush the pool, fill from the bottom and drain from the overflow (with pump off), in order to lower the CYA with the least amount of water possible? is it ok to continually drain from the overflow, or should I drain from the skimmer?


Second- Ive put a good deal of 20 baume Muriatic acid in my pool, and do not seem to be getting the results the calculator predicts. Just yesterday I put ~1cup in the pool, brushed it, circulated for 1 hour... and recorded a drop from 7.8 to 7.7. Any thoughts on what I may be getting wrong?

 

[zea3]

Hi, welcome to TFP! You may want to re-check the strength of your muriatic acid. How far did you want pH to drop? The most practical way to lower CYA is to drain and refill. CYA is not heavier than water, it stays pretty well mixed, however some people believe you can use a submersible pump in the deep end and fill from the shallow end to remove CYA without emptying the pool. You will get some mix of fresh water and old water but it helps in situation where a complete drain/refill is not an option.

 

[CarolineM]

1 cup of acid would only drop your ph to between 7.6 and 7.7. To drop to 7.6 you would need 10 oz, you put in 8 oz.

How much are you trying to drop your PH?

 

[ASteiny]

Thanks guys. I think i want my pH around a 7.4, but honestly I haven't put enough effort into measuring the actual volume added and comparing to effects yet (just a gut feel that I seem to be adding a lot of acid and getting not a lot of result). I think that my first step is to spend some effort on this before troubleshooting further.

In regards to draining the pool, what is the simplest way to do this (I'd prefer to avoid buying /renting an ESP and figuring out where to pipe it to).

 

[CarolineM]

Draining/replacing water I will leave to one of the experts to help you with.

 

[crusemm]

Why not just line up your spider valve for rinse, run your pool level down as far as you are comfortable (make sure to shut off skimmers if going below skimmer level) and then refill? I don't know Houston water prices, but if they are not prohibitive, that would be the fastest way. I think water table in Houston is pretty high, so I would only drain 25%-30% at a time. In about 4 cycles you should be down to 56

Current CYA	Volume after 25% Drain	Volume after fill	Final CYA
180​	11250​	15000​	135​
135​	11250​	15000​	101.25​
101.25​	11250​	15000​	75.9375​
75.9375​	11250​	15000​	56.95313​

 

[zea3]

If you have a regular pool vacuum hose you can connect it to the skimmer without the skimmer plate. Just remove the basket and insert the hose in the pipe opening. Attach the vacuum head and toss it in the deep end. Then you can set the multiport valve to waste and turn on the pump. I would drain about half the pool, refill and check the CYA again to see if you needed to drain anymore.

 

[Msch99]

Pool math will tell you what the addition will do. I had to adjust volume of pool when I started out. Depending on rain etc., still not perfect but close enough.

 

[crusemm]

Zea3, is it safe to drain that mich in Houston? I thought the water table was pretty high down there in smogland

 

[Richard320]

With a chemistry background, the math should be pretty simple for you.

Your pool's average depth is going to be somewhere between 4 and 6 feet, depending on how deep the deep end is and how much is deep versus shallow.

Let's say it's 60". 3" of water is 5%. 6" is 10%.

If you can draw just from the main drain, it ought to be easy to lose 6" at a time. and refill it within a few hours.
You can take that 180 CYA down to 160 in one shot no problem.

I replace water to reduce CH by emptying the spa into the pool and then empty the pool while I have the hose refilling the spa. That's 4-5" at a shot. 2" from the spa and 3" I can take before the skimmer starts sucking air.

I have maintained a pool with astronomical CYA. It'snot easy and I don;t recommend it. You have no choice but to use the FAS-DPD test every single time. No other tester will read the FC levels you need to maintain. That's a PITA. The OTO quick check is useless to you at the moment. The pH test will always be suspect. People that know better say if you take your reading immediately before the high FC reacts with the phenol red that it will be correct. I'm still suspicious. If you do get algae, you're really in a heap of it. If it is at all possible to replace water without incurring the wrath of the water company, do it. Pool maintenance is so much easier with proper CYA levels.

 

[ASteiny]

Thanks all for the help, and Richard, agreed that getting the dilution figured out is pretty simple, especially when i can test for CYA to confirm.. On further inspection here is the problem I have- My pool filter is a 60 sq ft. DE as mentioned. It has a backwash valve, one of the ones you twist and pull to reverse flow direction, but aggravatingly there is no multi-port valve or way that I can find to bypass straight to waste. I have an abundance of DE- so wondering is it acceptable for me to backwash to drain... or will that damage my filter? Is the best option to rent an ESP? Is there something I am missing in my inexperience?

 

[Richard320]

Backwashing to drain is probably not a good idea. The grids are designed to flow one way. Running them in reverse for a couple hours might damage them.

I have a hose spigot teed into my return line, which makes it easy.

The other alternative is a cheap submersible pump from the local hardware store or Harbor Freight. It will draw a lot less power than the pool pump, too.

 

[ASteiny]

Thank you sir. Now that i think about it, I have the hose spigot i could use, knowing Harbor freight, I can probably buy a pump for as much as i can rent from Home Depot.