Short Cycling

[donjoarm]

My pool is green and I am having a heck of a time with my filtration. I have a DE filter which will work fine for an hour (after backwashing) and then the pressure will rise and flow will virually stop. I have cleaned the filter with a commercial product and soap and water, nothing seems to work. The local pool store tells me there is nothing to add to the water to correct the algae until I have proper filtration.

This has been going on for two weeks. I am at the end of my rope. Any thoughts?

Thanks.

[duraleigh]

Hi, I'm surprised no one has responded yet. Didn't mean to overlook you.

Kill the agae FIRST. Running your pump and filter will clean up the dead algae and pool but you've got to get it dead before you can filter it out. Your pool store guy misspoke or he misunderstood your situation.

If you don't know how to get rid of the algae, there's a ton of info on this forum to read and get started.

The very first thing, if you want specific advice, is you must get a test kit and tell the forum:

Pool size (in gallons)
Pool type (vinyl or cement..inground or above ground)

FC
CC
TC
CH
pH
Alk
CYA

If you don't know what those are, post back and tell us and we'll get you the info.

Again, you must start killing the algae now or you'll never get out of your cycle.

Dave S.

[donjoarm]

I have a 20,000 gallon in-ground vinyl pool. I do not have the specific readings but the pool store stated that everything is in line with proper water balancing. I will have to take another sample and post the readings you requested.

In the mean time, what can I do now to start eliminating the algae without a properly operating filter?

[fog80]

are you using the bump handle after every few hours? My DE filter usually starts getting a high pressure reading every few hours when dealing with green algae. I then have to bump it and restart it for the pressure to temporarily go down.

Once most of the algae is gone, I backwash and fill the filter with fresh DE.

[donjoarm]

I have a Hayward DE 3620. I don't think it has a bump handle, it has a side monted multiport valve.

Would vacuuming to waste be beneficial?

[duraleigh]

In the mean time, what can I do now to start eliminating the algae without a properly operating filter?

"Don",

First, I am not a DE filter guy...I have sand. My assumption is your filter is working fine.....it's simply getting plugged up with algae.

Even if my assumption is incorrect, you have a green pool and Cl is the best cure.....lot's of it.

Without you posting those numbers, this is a little bit of a guess, but a pretty safe one. Put in 4 gallons of 6% clorox bleach all at once in the late evening. That will bring your 20k pool to 12ppm of Clorox and start whacking that algae. Now you need to keep it at 12ppm 'til your water clears and the only way you can do that is to test your water.

That'll give you a 24 hour head start but before we get too detailed on what to do next you'll need to help us by posting those tests.

Meantime, your pump should be running continuously....that'll help you filter out the dead algae and start clearing your pool.

Others will be along soon to advise you on your filter but it sounds like it's okay.

vacuuming to waste will not be helpful.

Dave S.

[donjoarm]

OK, I've got some numbers. I added 4 gallons of bleach last night.

FC .5
TC .5
ph 7.2
CH 200
Alk 70
CYA 100

I also have another problem-Air in the pump housing. I am trying to track down the source of that problem!

[PoolDoc]

I have a DE filter which will work fine for an hour (after backwashing) and then the pressure will rise and flow will virually stop. I have cleaned the filter with a commercial product and soap and water, nothing seems to work. The local pool store tells me there is nothing to add to the water to correct the algae until I have proper filtration.

Your pool store is full of it! Live algae plugs DE filters.

I'll never forget a night spent at a Girl Scout camp about 20 yrs ago -- they were my very first commercial pool customer, and it was my very first season, and the first and LAST time I ever let a customer pool turn green during the pool season. I got the call about 9pm, and was there from about 10:30 till 5am. They had a huge open pit vacuum DE filter that was BELOW water level. Every time the filter plugged, the water would overflow into the drain pit. The camp ranger and I were cleaning the filter every 20 - 30 minutes, all night long!

Kill the algae, and then filter it out. If you can, put your filter on recirculate. If you can't, turn it off, and add bleach till you kill the algae. Don't use other forms of chlorine, since you don't want it just resting on the bottom. On that GS Camp pool, it took 75 ppm of chlorine to finally terminate that algae. You can't go that high with vinyl, though.

With a 20K pool, you probably need to think in terms of 15ppm doses, though. That's around 6 gallons of household bleach per dose. Dose in the evening, and repeat everytime you find levels below 3 ppm. It may take many repeated doses, depending on how much algae is actually in the pool. Test with an cheap OTO kit (turns yellow from chlorine); DPD (not DPD-FAS) can bleach out, and cause you to think you have no chlorine, when it's really very high.

You'll probably get better results with low pH (~7.2) than with high pH (> 7.6) . . . UNLESS you had high CYA when you closed the pool, and now have low CYA. (Test to find out!). In that case, you'll need to RAISE the pH to around 8.0 with borax before you began dosing with chlorine. You'll get very fast algae kill, in that case, but you'll have to continue adding chlorine long after the water is clear, to get rid of all the chemical residue from bio-degraded CYA.

Do NOT mix in other algaecides. Adding copper when the chlorine is that high, will only result in stains. Adding foamy algaecides will just use up lots more chlorine. Polyquat could help, but it will be expensive, and you'd need to limit chlorine levels to something below 10ppm. And, it really works better if you've got a working circulation system, which you don't have at present.

If worst comes to worse, there are other ways. But they have complications and side effects. So, try chlorine first.

Ben

PS: Remember to add chems all around the pool, if your circulation system's not working. Pre-dissolve any borax in hot water.

[donjoarm]

OK. It's been a week and I have put 14 gallons of bleach in my pool over that time. I have the filter on recirculate since it continues to block every 20 minutes or so. The water is stilll green but the chlorine level remains high. Do I stay this course? I am brushing regularly as well. Thanks for the input.

[duraleigh]

Don,

You will have little success unless you get a drops based test kit and can test your water several times during the day. With that very high CYA level of 100, you need to put enough Cl in there to bring it to 25ppm and KEEP IT THERE until your water clears. As long as your water is green, you're not keeping your CL high enough.

Dave S.