Found algae under main drain cover. Can I remove?

Dan Morrill

Member
Jun 8, 2020
15
London Ontario
SLAMMED a month ago, but have had a couple small algae spots come up if I don't brush the pool for 4-5 days despite very adequate FC levels. They brush away easily, but obviously it meant I didn't get everything.

Anyways, decided to investigate more closely under my main drain cover, and what do you know! Green!

It's a vinyl, inground pool. Drain cover is held by two screws. Can I unscrew them to get at the algae or will it mess up the liner?
 

zea3

Mod Squad
TFP Expert
LifeTime Supporter
Jul 10, 2009
12,545
Houston, Texas
Post a picture of the main drain. How old is your pool? I don't know if you have a similar regulation for main drains in Canada, but in the US all pools built after 2007 have to have anti-entrapment main drain systems. Older pools may be anti-entrapment compliant with new anti-entrapment drain covers. Those snap into a base plate on the drain.
 

Mike1162

Silver Supporter
Jun 13, 2015
667
N Tonawanda, NY
You can remove the cover. Once the cover is off you'll see maybe a dozen screws that hold the flange. Those are the screws you don't want to remove. I used a 15 lb dumbbell to help hold me down. Exhaling before you dive down also helps.
 

JJ_Tex

Bronze Supporter
Jul 17, 2019
1,308
Prosper, TX (DFW)
I know nothing about drains and vinyl liners, but if you are uncomfortable taking off the drain, maybe you could try something like this:

1. Dive down with a garden hose (or something else with some pressure) and spray it into the drain to help break up the algae. Get in as many holes and different angles you can.
2. Get a turkey baster full of bleach, and squirt that into the drain cover (with the drain off for a few mins) to kill the remaining algae
 

JohnT

Admin
Mod Squad
TFP Expert
Apr 4, 2007
9,827
SW Indiana
The area around the main drain is one of the highest flow areas in the pool. With sufficient chlorine in the water, algae isn’t going to grow there under any circumstances. Algae can’t hide in chlorinated pool water. The chlorine will kill it if there is enough chlorine.

Removing and replacing that faceplate is a major chore unless you have SCUBA equipment, and it isn’t going to solve your algae issue.
 

Dirk

Gold Supporter
TFP Guide
Nov 12, 2017
5,094
Central California
If you do decide to work underwater by breath holding, please be sure to have someone help, just by standing by on the surface but prepared to fish you out. Shallow water blackout can and does occur in swimming pools, of any depth, in as little as two minutes or less. Doing things like hyper-ventilating before you dive and/or exhaling to help you stay down only increases the likelihood. It's caused by lack of oxygen to the brain: you faint, basically, and then drown. Use caution. Work in very brief intervals.
 
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zea3

Mod Squad
TFP Expert
LifeTime Supporter
Jul 10, 2009
12,545
Houston, Texas
John has a good point. Do you get good flow through your main drain, or do you have it shut off most of the time? If it is open and gets good flow you may need to bump up your daily chlorine target level once the algae is cleared. If you keep it shut most of the time make sure you open it up for an hour or so every couple of days to make sure chlorinated water gets down there.
 

Dan Morrill

Member
Jun 8, 2020
15
London Ontario
Well, this was going to lead to my next question. With my pump running, I don't feel really any flow going through there.

This is my first full summer with the pool, bought the house late last season. I don't know much about pool plumbing as it is, so I'm not even sure if that is normal or not.

I have two holes in my skimmer basket. The left one is the suction line pulling into my pump. The right side I was told goes to the main drain. Is that right?

20200802_151818~2.jpg
 

Dirk

Gold Supporter
TFP Guide
Nov 12, 2017
5,094
Central California
If it's like mine, the main drain won't pull water unless there's some sort of diverter plate in the skimmer. I'm not sure what they look like, 'cause mine was missing. Yours looks to be the same situation.

Sorry to be the safety cop... you do understand that people get trapped underwater by main drains, right? Removing the cover while the pump is running is dangerous. Sticking your hand in there even more so. Please be careful with what you're doing, and don't leave it like that for any length of time. I don't know what a 1hp "Super pump" is capable of, but some pool pumps can eviscerate a person (mine can), so the danger is real.
 

Dan Morrill

Member
Jun 8, 2020
15
London Ontario
Thanks for the info everyone.

Cover off, algae scrubbed away, and cover back on in under 10 minutes. I've also made a makeshift "diverter pipe" to get water flowing better through the main drain.

Now for a (hopefully) quick SLAM to kill off all the algae.