new user, old pool, trouble with algae

[ksukris]

I am having an especially difficult time with algae this year. I have a 24000 gallon inground vinyl liner, sand filter, 3/4 HP pump. When I took the cover off, water was dark green and cloudy. Usually lots of shock clears it up in about a week, but after 3 weeks I'm still dealing with light green cloudy water. Here's what I've used so far:

1. an entire 40 lb bucket of granular shock
2. 15 lbs of alkalinity up followed by 30 lbs of soda ash to get ph to 8.0 so I could use "green to clean" (had good results in the past)
3. 1 container "green to clean" with 8 lbs shock, followed by another 6 lbs shock 12 hours later
4. 1 bottle "pool magic" to eat up the dead algae (no results)
5. changed out sand in filter
6. 10 lbs power powder
7. running pump 24/7 on "recirculate" (before today i was filtering)

here's what my tests show (pretty consistent for the past few days)
TC >10
FC >10
ph - between 7.8 and 8.0
TA 180
CYA 150

any advice? i've removed as many leaves as i can with my "blue devil" but who knows what's down there since i can't see the floor of the pool. also brushing daily. just give it more patience? i'd be tempted to drain and start over, but my main drain doesn't work and draining is a nightmare! i know my circulation is a problem without main drain, but i've been circulating through the skimmer only for 5 years, never had this much trouble before.

[aylad]

HI, and welcome to the forum!!

My first piece of advice is to slow down a little bit and stop throwing things at the pool trying to get it clear. The second piece of advice is to stay away from the pool store that is selling you all this stuff!!

I'm assuming the granular shock you used was dichlor, and that would explain why your CYA is so high. In order to get the pool cleared up, you'll need 4 basic things: 1 )a good test kit (see the link for test kits in my sig) because testing is going to be crucial to getting the pool cleared, and you'll need to be able to test HIGH amounts of chlorine, 2) enough bleach to maintain a shock level of 25 ppm of chlorine for an extended amount of time, 3) a working pump and filter system, and 4) LOTS of POPP (pool owner patience and persistance).

You'll need to stop using any form of stabilized chlorine, which is why we recommend bleach. The increased problems you have with algae this year are almost certainly happening bvecause you're not keeping your chlorine high enough. Take a look at the "best guess chlorine chart" link in my sig for more info about that. Also, I gather that you're using test strips for testing, and they're simply not going to work while trying to clean up a messy pool. Can you let us know what type of pump/motor, and what size/type of filter you have?

[lint28]

Im not expert but isnt a 3/4 hp motor a little small for a sand filter on a 24k gallon pool? If it worked in the past i doubt that its your problem but it does seem a little small. I recently had the same issues and figured the sand was just old. I ended up just replacing the filter and putting in a new pump. I increased the pump from 3/4 to 1hp and it looks great now (i used just shock, yellow out and chlorine tablets)

[ksukris]

Yes, I'm a pool store addict. Trying to rehabilitate, since the worse off my pool is, the more money they make! While I'm waiting on a test kit, here's what kind of pump/motor I have:

New (as of this season) 3/4 HP pump - not sure what brand
Hayward S220T sand filter with 250 lbs sand - new filter in 2010, new sand as of Monday

Thanks for your help

[aylad]

A smaller pump with larger filter is always better than a smaller filter overdriven by a pump that's too large. The equipment gurus should be along shortly ( Pooldoc? mas985?) to verify this, but I would think a 3/4 HP is fine for that size pool. Even though it'll take longer to turn the total water volume over, the filtration actually should be better.

With a CYA of 150, then you'll need to get the chlorine levels up to 25 ppm, and keep them there by testing and adding more chlorine as often as you can during the day, until the green clears up. I would also keep the pump running 24/7, brushing the pool daily, and keep an eye on your filter pressure, backwashing as needed, but not until you see an 8-10 psi rise in pressure. Considering your CYA levels, I would strongly advise you to use bleach, or liquid chlorine. In 24K gallons of pool water, each 2 gallons of 6% bleach will raise your chlorine by 5 ppm, so you can use that as a guide when figuring your chlorine additions. As I said before, though--you're going to need to be able to test high chlorine levels to get this one cleared up.

[ksukris]

I've had the house/pool for 8 years, and never had a problem with the 3/4 HP pump before now. I should say I just replaced the motor, not the pump. I'm getting a test kit for high chlorine levels and some bleach today, I'll report back as soon as I can retest.

Should I be running the pump on filter or recirculate? I won't need to backwash if it's just on recirculate, right?

[aylad]

You won't need to backwash if it's on recirculate, assuming everything is plumbed and working like it should. NOrmally we would advise people to run the pump on filter while the mess is being cleaned up, and with a larger filter on a smaller pump, I'm still inclined to advise you that way. However, this year we've had a ton of folks who are having problems clearing up the dead algae once it's killed, and Pooldoc believes that sometimes it's due to forcing the dead stuff through the sand and actually having it break up into smaller pieces than the filter can catch. So....if it were my pool, I'd probably keep it in filter mode. However, if you want to leave it on recirculate until it's all dead and THEN switch back to filter to get it all out, you can do that too. Either way works, but if your filter is efficient at getting the dead stuff, then the recirculate option may just take a little longer.

Janet

[PoolDoc]

I'm getting a test kit for high chlorine levels and some bleach today, I'll report back as soon as I can retest.

The locally available "high chlorine" tests are not what you need, 98+% of the time. Get a K2006 or K1515 (test kit page linked in my sig) online. Meanwhile, get a local OTO (see kit page) kit for now. If the Walmart's in your area have the HTH 6-way, those are an excellent value (they are a private label Taylor kit!).