How To Treat Green Pool Water?

Getting a green pool clean and clear can be an intimidating concept for many. I get many requests to drain green pools because the owners believe it to be a total loss. What can you do if your pool has been neglected, or for whatever reason, it has begun looking dark and murky?

Clean or backwash your filters. Shock the pool possibly several times with chlorine or non-chlorine shock to kill the algae. Use a strong algaecide as needed. You may need a clarifier to clear up the pool. Bring everything into balance, and you’ll have a nice clear pool.

Read on below to get the complete process on how to get a pool back to being crystal clear.

Don’t Neglect Your Green Pool

So what if you bought a house with a pool, or your winterized or otherwise clean pool turned green, what are you going to do? Well, first things first, don’t put off taking care of it. It will only get worse and harder to clear up.

Here’s a little disclaimer, if you don’t have the mechanical ability (you know who you are) please don’t attempt to maintain your own pool. Hire a professional, they are worth the expense. If you know your way around basic tools, aren’t intimidated by taking things apart, then owning a pool will be a breeze. This article assumes you have these basic abilities to do what we are discussing. If not, we will add some other tutorials for each portion of this post and link to them.

If the pool has turned green, this is the post for you. Or, if the pool just needs basic care to keep it clean, check out this other post on 3 weekly tasks that will keep your pool clean.

Bad Pool Pump and Filtration Can Mean Green Pool

First things first; inspect the pool and the pool equipment. A visual check will help you assess the situation. Let’s assume the pool is green. Obviously, if the pool is green the situation is critical, but we need to still determine if it’s chronic or acute. Can you see into the pump basket through the lid? Most pumps have clear lids, you should be able to see water in there, or is it full of leaves? If it’s full of leaves you should open the pump lid and empty the basket. If the basket is broken, it should be replaced. Amazon or your local pool house should have what you need. Here’s a link to the Pentair Intelliflo/Whisperflo pump basket that is actually shown below.

Now with an empty basket and a pump pot full of water start the pump at the timer. You should be able to see the water moving through the pump. After a few seconds, you should see the pressure gauge on the filter jump up. Don’t be alarmed if you don’t see this happen, I can’t recall how many pressure gauges in the field I’ve seen that aren’t working. If yours isn’t working, replace it. When the pump is actually moving water, you should see some evidence in the pool itself that water is moving. In murky water, you may only see the surface of the water being disturbed by bubbles or water movement. If you see no movement and you’ve confirmed that there’s water moving in the pump then the filter likely needs to be cleaned.

Pool Filters Can Bread Algae

Cleaning the filter is a broad subject just on its own. Just a quick safety disclaimer; pool filters are under a lot of pressure when in operation. If you don’t understand how to fix or maintain them, hire someone who does. I’ve known very experienced professionals that have been injured because they didn’t respect the power that is present in a pool filter.

Due to the various types of filters, you may need to break yours down, or you can backwash. Again, this article assumes you know what’s what, so we’ll address all that later. Go ahead and service the filter and make sure there are no blockages preventing the water from moving. Cartridge filters may need new cartridges. DE filters may need new grids. Sand filters may need new sand or laterals. Once everything is back together, check the pump basket, and the skimmer basket to make sure they are clear. Now you should see the movement of the water when you turn on the pump.

If you have more equipment, such as heaters, ozone, chlorinators or other attachments there should be a way to divert the water from going through them. You’ll want to confirm the water is not being restricted as it goes through that equipment as well.

The Heart of Your Pool’s Circulation

Hopefully, at this point, you are confident that your filtration system works and it is ready to do its job, namely, clean the water. It’s important to understand that it’s the sole purpose of the pump to pull water from the pool and force it through the filters and return it back to the pool. If you have multiple pumps on your system, those other pumps serve other functions, but for the purposes of this article, we are talking bout the primary filtration pump. We will post later about single speed vs. 2-speed vs. variable-speed pump. I sense a top-10 list in there somewhere!

If you suspect a failing filter pump, check out this article on noises that pool pumps make that are about to fail.

Running The Pool Pump On A Green Pool

In connection to the pump is how long should it run each day. Now I won’t get into the calculation here but its been industry standard for many years now that we want to put that entire pool through the filter at least once a day. There are some variations to this thinking depending on where you live and the efficiency of the pump/filter combo, but this is a good rule of thumb to go by.

A 1hp pump connected to 1-1/2″ plumbing on an average size (approx. 12,000 gallons) pool that’s relatively close to the pool will be around 6hours per day.  Just keep in mind ‘rules of thumb’ are just rough estimates so you will have to play with this over the long term, but its a good place to start. The one main caveat is if the pool is green and we are doing a clean-up, in that case, you will be running the pump for as long as possible every day, 24 hours a day if possible, for at least 4-5 days.

Time to Clean the Pool

Now that we have good water movement, good filtration, and our timing is more or less set. Now we need to help the system clean the water. The first way we help the mechanical filtration of foreign materials is by limiting the load put on the mechanical filtration system. That means removing additional materials before they need to be filtered out.

Skimming, or netting, debris from the pool is the first step. In a clear blue pool, this is a relatively straight forward process if you see it scoop it out. A green murky pool, on the other hand, you can’t see the bottom so you may just have to skim the surface and do some, what I like to call, ‘test scoops’ from the bottom to see if there is much-hidden debris to worry about. Just get what you can and leave the rest because as the pool clears up you’ll be able to get the rest out later.

Vacuuming Your Green Pool

A great way to clean out submerged debris in addition to netting it out is by using a mechanical vacuum like a Poolmaster Leaf Vac. These are most effective when you can see what’s happening beneath the pool surface. The leaf vac keeps the debris from entering the pump/filter thus lessening the load or demands on the system.

If the debris at the bottom if fairly minimal and manageable, you could use the classic or standard pool vacuum head or brush vac head for vinyl and fiberglass pools that use the suction of the pump when connected to a vacuum hose. Everything you vacuum will enter directly into the pump/filter. If you have a lot of leaves you will have to frequently stop to empty the pump basket or vacuum strainer if you use one. All pool owners should own a vacuum head and hose. If you want to maintain your own pool, this will be the only way you get it clean and clear.

Brushing The Pool Down

As the removal of the debris proceeds, brush the pool down. Make sure to use the correct brush. Don’t ever use metal or stiff bristle brushes in vinyl or fiberglass pools! That will be a sure way to destroy the pool, or even pop and drain it. Soft brushes in varying sizes are available for vinyl and fiberglass. For plaster, pebble and glass bead pools you can use pretty much any bristle type you like.

In every pool, there are always a few ‘dead’ spots where the circulation of the water is minimal. These spots are usually around the steps or swim outs. Oddly shaped features and in the corners where two perpendicular elements meet can also be dead spots. Make sure to brush these spots regularly.

In a clean-up scenario, you will want to brush the pool as often as possible. This allows the circulation system to pick up debris that would otherwise be stuck to the wall or floors. Brushing the pool is probably the single most effective activity to keeping a pool clean, or getting it there. You really can’t brush too often…as long as you are using the right brush.

Swimming Pool Water and Chemical Balance

Once all the maintenance items are checked off, its time to address the water/chemical balance. In a clean-up scenario, things can be a little tricky, but the nice thing is that you really can’t mess things up too bad. You’ll want to start by testing all the basic water parameters; chlorine, pH, and alkalinity (no this is not the same as pH). Some areas you will want to also look into your hardness levels and even copper & iron. Especially if your source water is known to be high or low in these areas. And just so we are clear, some people are chlorine sensitive, here we are talking about the most efficient way to clean a pool in general. We may hit on chlorine alternatives in a later article.

Algaecides Help Clean the Green

A key point of taking a pool from green to clean is killing the algae. We need to make the water inhospitable for the algae to live in. There are algaecides on the market but won’t act as your primary chemical. Use algaecides as a supplement to good water chemistry. Bring your pH into balance ~7.4, then bring your chlorine levels up to about 10 ppm. You’ll want to maintain these 2 parameters until the pool turns blue. Use algaecide per the directions, but keep the chlorine and pH levels correct through this process. Once the pool turns blue, you can let the chlorine fall naturally to about 7.0 ppm. At the point that the water is cloudy blue, the algae are more or less dead or dying off and you should see whitish powder falling to the bottom.

What Do Phosphates Have to do With Green Pools?

When algae die, they release their main food source back into the water, phosphates. You’ll want to get a good phosphate test kit, you’ll notice the levels will climb as the algae die. Once the phosphates hit about 500 ppb you’ll need to add phosphate remover. Eight hours later you will need to vacuum the pool. This process may need to be repeated a couple of times, as you get to the end the pool will naturally clear. Clarifiers and enzymes on the market will speed the post-phosphate remover process along. Once this process is done, the chlorine should naturally fall to 4.0-5.0 ppm which is where it should stay when the pool is in use.

So that’s that. When you end up moving to a new home that has a pool you didn’t want, don’t neglect it. Get in there quick to keep the chemicals and mechanical equipment in balance.

Now that you have your pool clean, pop over to this article to help you keep it that way. It’s my Ultimate Swimming Pool Maintenance Checklist

Keep in mind, if anything in this article or any processes seems overwhelming to you don’t attempt to do them. Hire a professional to get your pool squared away. Especially when it comes to administering chemicals. It doesn’t take much to do serious damage to the maintenance person or the bathers, so please respect pool chemicals.

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