New Owner - Old Pool with Algae

[team5d]

We moved into a new (to us) house in TX this week with a concrete inground pool (~15,000 gal) with sand filter that was built in the mid-80's. We've never had a pool before and are really coming into this without knowing anything about maintaining a pool (dumb, I know). I don't know how the previous owners maintained the pool. The pool didn't look bad when we moved in 4 days ago but it has gotten greener and greener each day. The first time I tested (with cheap test strips) the TC and FC were zero. I've been adding a lot of shock to bring the FC up. The levels now show TC 0.5, FC 1, pH somewhere between 7.2-7.8, Total Alk 80, Cyanuric Acid 30-50.

I'll get the "good" HTH test kit at Wal-Mart today along with a cart load of bleach. I have some Algaecide that I haven't used yet.

We have been brushing and vacuuming but our vacuum is manual and doesn't seem to have very good suction. The filter is running 24/7 right now.

What else should we do to get rid of this algae? What more info do you need from me?

My three little boys are dying to play in the pool. Do I need to keep them out till everything is crystal clear and blue again? Thanks!

[PoolDoc]

The pool didn't look bad when we moved in 4 days ago but it has gotten greener and greener each day. The first time I tested (with cheap test strips) the TC and FC were zero. I've been adding a lot of shock to bring the FC up. The levels now show TC 0.5, FC 1, pH somewhere between 7.2-7.8, Total Alk 80, Cyanuric Acid 30-50.

Assuming those results are valid, your chlorine is too low, way too low. Everything else is OK for now. (Some tweaking will be needed later.)

15K gal pool => PF= 8. One gallon of 8.25% bleach contains about 0.7 lbs of chlorine gas, so a gallon adds 8 x 0.7 or ~5.5 ppm of chlorine to your pool.

Add 3 gallons tonight. Test tomorrow PM with OTO. If you get a DARK yellow OTO reading for chlorine, add 1 gallon the following PM. If you get medium to light yellow, add 2 gallons. Clear, add 3 gallons.

Continue till algae is gone.

Stop using the "shock" till you tell us EXACTLY what kind it is. Much of the stuff sold today is better used to clean your toilet bowl.

I'll get the "good" HTH test kit at Wal-Mart today along with a cart load of bleach.

The only "good" kit at Walmart is the HTH 6-way (made by Taylor). If your Walmart doesn't have that one, just get a cheap OTO / phenol red drops kit.

I have some Algaecide that I haven't used yet.

Unless it's polyquat (www.poolsolutions.com/polyquat.html) do NOT use it. Give it away, flush it down the toilet, whatever. Just don't put it in your pool.

We have been brushing and vacuuming but our vacuum is manual and doesn't seem to have very good suction. The filter is running 24/7 right now.

What kind of filter and pump do you have?

What else should we do to get rid of this algae?

1. Read the Best Guess page, linked in my blue signature block.
2. Order a K2006 test kit (see link in blue block).
3. Use bleach to keep the chlorine in the DARK yellow OTO range, till the algae is gone.
4. Do NOT let the pool store "pool-store" you -- no shock, algaecide, phosphate removers, calcium, alkalinity, etc.

My three little boys are dying to play in the pool. Do I need to keep them out till everything is crystal clear and blue again? Thanks!

Once the pool is well-chlorinated, and clear enough so that they can't disappear and die on the bottom unseen and un-rescued, they can swim. Use old swimsuits -- people are VERY chlorine resistant; some swimwear is not (especially women's fashion swimwear!). Depending on what ELSE has been put in the pool, the water may be irritating to their skin and eyes. So limit their first swim to 15 minutes. Wait a few hours, and see if any of them are itchy or have burning eyes. If so, you'll probably have to put off swimming till you've had 2 -3 days of full sun AND high chlorine. (Solar UV + chlorine break down stuff chlorine alone won't.)

In particular, if you've used any algaecides besides polyquat, or some "metal removers" the pool may be unpleasant for awhile.

Good luck!

[team5d]

Add 3 gallons tonight. Test tomorrow PM with OTO. If you get a DARK yellow OTO reading for chlorine, add 1 gallon the following PM. If you get medium to light yellow, add 2 gallons. Clear, add 3 gallons.

Added some chlorine granules (the last of a bottle we had in the garage) and 3 gallons of bleach last night. Bought the HTH 6-way kit at Walmart and tested this morning:
TC 10+
pH ~7.3 (darker than 7.2, lighter than 7.5)
Alk turned pink at 100 and red at 110
Total Hardness - did not turn red with the indicator
CYA 38

What kind of filter and pump do you have?

Hayward Pro Series High Rate Sand Filter Model #S244T
Pentair SuperFlo High Performance Pump
(I'll add those to my profile.)


I brushed this morning and, for the first time, I could see the brush on the bottom of the deep end (6 1/2 feet) AND I could see it making white brush lines through the green at the bottom and stirring up clouds of green.

I backwashed the filter (the site glass was nasty looking!) and rinsed. I have been backwashing and rinsing daily for the last 3 days. The filter has been on 24/7.

Should I shut the filter off and let the algae settle to the bottom so I can vacuum it? I'm assuming I should vacuum to waste.

I have an unused bottle of KemTek Ultra Clarifier. It doesn't list ingredients other than "Cationic Particles". Is that something I should use or just return it to Lowes?

Thanks!!

[PoolDoc]

1. If the chlorine is high, and the algae appears dead, you can turn the pump off, and see if it will settle. Make sure the chlorine REMAINS high during this process.

2. If you want to try the clarifier, try to settle it FIRST. Some clarifiers help settling; others don't.

3. Don't backwash too much -- doing so reduces your ability to remove the dead algae. Let the filter pressure increase to 5 psi ABOVE the clean filter pressure, before backwashing.

[team5d]

3. Don't backwash too much -- doing so reduces your ability to remove the dead algae. Let the filter pressure increase to 5 psi ABOVE the clean filter pressure, before backwashing.

Can you explain #3? We are new to pool ownership and learning the basics as we go. I've been backwashing based on the advice of a local pool guy I spoke with on the phone who said we should be backwashing once daily until the algae is gone. We have someone else coming out in a couple days to look at our pool and equipment and give us a crash course on owning a pool.

Also, how would I find out what our clean filter pressure should be? It's been running pretty consistently at 17psi both before and after backwashing. I found and downloaded the manual for our pump but it didn't have much info. Can you recommend any good links or sites for learning more pool basics? Thanks!

[PoolDoc]

On a sand filter, as the cycle progresses, the dirt becomes PART of the filter media, allowing you to filter out finer and finer particles. When you backwash too often, you break this cycle.