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How to control foaming
and scum deposits, in swimming pools? Foaming and
scum formation are serious detractions from the
goal of crystal clear swimming pool water. A few
pool chemicals: such as biguanide and "quat" algaecides
do cause very low levels of foam. This level of
foaming is not excessive and is fairly
inconspicuous. However, if there is an air leak
in the return lines, this can lead to a higher
level of pool water foaming and the creation of
unacceptable water conditions. While an
anti-foam can help, the problem is more of a
mechanical nature - fix the air leak! Scum
formation occurs when body oils, cosmetic
residues, waste and chemical byproducts conspire
to form insoluble materials. It is not, usually,
a major problem and can be controlled and
eliminated with the use of cleaning agents or
enzyme products. If problems arise, refer to the
Pool Problems Page, as
a source of problem-solving information, broken down into
various categories. Scroll down the page and click on the linked
or images, in the archived answers below, to access additional information, on that topic or product.
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Problem-Solving Information, in a question and
Control Without Causing A Foaming Pool?
We just moved into a house with an
in-ground swimming pool. Our old house had an above-ground
pool. One of the things that I disliked about the old pool
was the foamy water problems caused by using an algaecide. I
don't want to ruin the look of this pool. Are there
algaecides that don't foam? Willing to listen.
Frank R., Wayne, NJ, 6/24/2012
Actually, there are algaecides that do not cause foam. The
best choices are: polymer (polyquat) algaecides or chelated
copper algaecides. The polymer algaecides are more
expensive, but are highly effective against most types of
algae. The chelated copper algaecides are very
cost-effective and are excellent in vinyl pools and for use
against the common varieties of algae, as well as mustard
algae. While it is true that the very common "quat"
algaecides do have a tendency to foam, it is not normally
problematic or unsightly. In those instances, where
unsightly pool water foaming is occurring, it is highly
probable that there is an air leak in a suction line. A
pinhole sized leak can allow air to be sucked in and this,
in turn, leads to aeration and foaming. Something worth
checking into? Instead of using algaecide, which can cause
foaming, you could add a
shouldn't have to use algaecides, thereafter, and it will
reduce your chlorine usage. I hope that I have been of
Sincerely. Alan Schuster, 6/24/2012
Dear Alan, I found your website after
searching for a reason for the frothy foam in my inground
pool. The pool company opened our pool last week, and as
soon as the water level was high enough and I turned the
filter on, foam formation began. After a few days of this, I
called them and they gave me a bottle of defoamer. This
worked when applied, but the next day I had foam again. The
foam does dissipate when the filter has not been on for a
significant amount of time. When I contacted them again,
they said to let the filter keep running, that perhaps
someone had "added soap and pulled a prank." They said they
do not use algaecides that foam, and insinuated that this
was somehow MY fault. I find this highly unlikely, as my
pool area is very secure, and I have done nothing to the
pool except turn on the filter. They also closed my pool
last fall for me. In addition, when I emptied the skimmer
today, I noticed a gummy greenish-gray substance inside the
walls of the skimmer. I have no idea what this may be. Could
it be related to the foam? It has been suggested to me that
the wrong kind of algaecide was added when the pool was
opened (they did add a quart, although I don't know the
brand). Your website also mentioned a leaky air return. Do
you have any suggestions for me? Should I continue to wait
to see if the foam goes away, or contact the company that
opened the pool again and maybe suggest to them that they
check the air flow? Thanks for your help. I found your
website extremely helpful and well organized! Sincerely.
Kathie H., Leicester, MA, 5/18/2010
It is not possible to rule out vandalism. It does happen!
The "gummy" material could be coagulated dead algae and
debris. A shock treatment could be in order. As for the
blame, no one has to be at fault. Algaecides that contain
ingredients like or similar to dimethyl benzyl ammonium
chloride are known to cause some pool water foaming.
Usually it is at acceptably low levels: that is unless there
is a leak in a suction line. It would not be unusual to
have such a leak after a dormant winter and spring startup.
The antifoam will help and, if it is due to an algaecide, it
will taper off. The algaecide could have been part of the
winter closing or the spring opening. I suggest that you
shock the pool and give it a bit more time. If things do not
improve, get back to me and we'll try something. Algaecides
such as polymer based, chelated copper and silver do not
cause foamy swimming pool water problems. Something to
consider, in the future? To better assure proper overall
pool water chemistry, visit a pool store that has a very
reliable, professional lab such as a
WaterLink SPIN Lab or Pinpoint
system, rather than a less accurate test kit or strip
reader. To locate a dealer near you, go to:
LaMotte Professional Testing Center Locator I hope that I have been
of assistance. Good luck.
Sincerely. Alan Schuster, 5/19/2010
► A Matter Of
Our pool pump/filter was not working
for a while, and during that time our pool became green. We
now have our pump/filter working, so we began the process of
"de-greening" our pool. Well, in this process, we used too
much algaecide in our pool. We now have a very fine soapy
film on the pool. Help!! I have backwashed several times,
but I can not seem to get it cleared up. It is getting
better with each battle, but is there anything else I can
do? Or, should I just keep backwashing, several times a
day, and shocking each day until it clears up. Thanks.
April and Tom R., 5/7/2009
You probably added an algaecide with dimethyl benzyl
ammonium chloride or something similar. This type of product
does have a tendency to cause foaming. An air leak in the suction lines, which is not unusual, especially, at pool
opening time, will worsen the situation. Check all
connections! To control the foaming, add some Spa Formula
antifoam, as directed. More is not better! I suggest that
you stop using that type of algaecide and consider either a
polymer formula or a copper algaecide; neither of which
causes foaming. Use the antifoam, as needed, until then. The
foam problem should dissipate, as the season progresses.
Backwashing or shock treatment should have no effect on the
foaming. Adding an enzyme product might help eliminate some
of the foam and aid in the cleanup. Instead of using
algaecides and chlorine, why not add a
chlorine generator and mineralizer combination. It requires
no installation and can replace both products. I hope the
information proves helpful to you.
Sincerely. Alan Schuster, 5/7/2009
► Air Bubbles?
Alan: After opening our pool this
spring, I have noticed bubbles coming out of the pool jets
the entire time the pump is running. We have a 30,000 gal
pool on a sand filter. Is the problem due to some sort of
leak in my system? The pool is equipped with an ionizer.
that you have an ionizer and that should rule out the
possibility of an algaecide causing the pool water foaming.
It would not be unusual for this problem to occur, after the
springtime pool opening. I suspect that there is an air leak
in a suction line - somewhere between the
skimmers and the filter. Check all the connections. Good
luck and I hope that I have been helpful.
Sincerely. Alan Schuster, 5/15/2012
► Scum And
I was just wondering what is the best
chemical solution for cleaning my pool. To get all the body
oil's and lotion off, along with the scum.
Al F., 3/7/2010
Shock treatment could remove some of the deposits. A pool
cleaner, formulated not to cause foaming, could help remove
some. However, the best choice might be an enzyme product.
There are products that allow enzymes to be added to the
pool water, where they will help decompose oily residues.
Many enzyme treatments, are specifically formulated, for
this purpose. Some cleaning products contain enzymes, as
well. The enzyme approach would be my choice. Good luck and
I hope that the recommendations help.
Sincerely. Alan Schuster, 3/7/2010
I think that some of the neighborhood
kids threw some bubble bath or detergent into my pool. The
foaming just happened so quickly, so I'm fairly certain
that's what happened. Is there something that you can
recommend to deal with all of this froth? I need help.
Joe O., Levittown, PA, 8/1/2004
I guarantee nothing, but here are a few things to try.
Adding an Anti-Foam Product (used in spas) will help knock
down the foam, but is not a cure all. Adding an Enzyme
Product will help digest or decompose the foaming agent, but
it will act slowly. Add a dose of "quat" algaecide (dimethyl
benzyl ammonium chloride) to the pool. This product is
incompatible, with both the bubble bath and detergent, and
will chemically react with those materials. This will, most
likely, cause cloudiness that should be treated with shock
and one of those "Blue Clarifiers." Follow up with an Enzyme
Product. Good luck with the problem.
Sincerely. Alan Schuster, 8/1/2004
Hi Alan, my name is Carlos, and I have
a pool. I've emailed you once before and you were a great
help at answering my question. What you do is really nice.
I've been searching around your site to try to find an
answer to my new question. Recently, I started to notice
that small little bubbles would appear in the pool, when I
would make little splashes. It looks as if it had some kind
of soap or something. I was wondering if you know of any
problems like this. If so, what solutions are there? My pool
is about 20x35 (estimate) and it is inground vinyl lined. I
also have noticed small little indentations at the pool
floor slightly larger than a quarter. I've read on your site
that it could be from erosion of the sand caused by rain. Is
there any solution to this problem, as well? Thank you for
Carlos M., 1/15/2005
Most likely the bubbles are caused by the use of "quat"
algaecides. Products with ingredients similar to dimethyl
benzyl ammonium chloride have a tendency to foam. It doesn't
sound severe, so I suggest that you discontinue use of all
such products. Eventually, the problem will dissipate. Not
all algaecides cause foaming. Try using a chelated copper or
polymer algaecide instead. The problem with depressions does
not appear to be erosion, as that would not be limited to
spots. Possibly the depressions are due to toys, certain
activities or a pool vacuum. There isn't much that you can
do about this, if it is as you described. You might try
using a toilet plunger, to tug on the spots, in order to
smooth out the liner. I hope that this information will be
Sincerely. Alan Schuster, 1/16/2005
► A Foaming
Pool Problem And More?
We have been trying to "open" our pool
for approximately one week and cannot seem to keep the pump
working because it keeps clogging up with foam. The foam
appears to lay on the surface and has a scummy appearance
when the pump is not being used. When the pump is running,
the foam gets worse - much worse! The water is very cloudy
and is bluish/green in color. We have tried adding shock to
up the chlorine level, but that only worsened the situation.
We have tried adding a multi-purpose product, but that only
helped temporarily. Most recently, we have tried draining a
good bit of the water and refilling it with fresh water.
Nothing seems to help! The pool is approximately 44,000
gallons. Comments, suggestions? Please send. Thank you!
Kathy M., 5/27/2007
You have more than one problem: algae, no filtration and
probably an air leak in the return line. Start by raising
the Free Chlorine level to 5-10 PPM. Add 4-5 pounds of shock
every few hours, until the Free Chlorine is raised and
maintained. If necessary, set the filter to recirculate, but
keep the water moving. The algae is clogging the filter.
Make some progress on the Free Chlorine front and the battle
over the filter will be solved. Clean the filter, as needed.
A leak in the suction lines can cause foaming. The algae
is not helping and, if you added a "quat" algaecide, it may
have contributed to the foaming. Check all connections. I
hope that the information will prove helpful.
Sincerely. Alan Schuster, 5/28/2007
► Pool Is
I recently use a tile soap [mixed with
acid and water] to clean my pool tile. My surprise that they
don't use a low/no sudsing formula. My pool now has bubble
[originating at the hot tub pour-over] that it NEVER had.
I've added a defoamer once, which worked pretty well, but
then the bubbles returned rather quickly. Any suggestions
would be appreciated. Thanks.
Todd G, 2/16/2005
product was intended to clean shower tiles, the end result
is not unexpected. In a shower the suds go down the drain.
In a pool, the suds end up in the water. If the product was
intended for pool use, it could or "should" have been
formulated with low foaming detergents. Antifoam will help,
but is only temporary. Try adding an enzyme product to the
pool, as this can help digest (decompose) materials causing
the problem. It may take a while to make a noticeable
difference. Good luck and I hope that I have been of some
Sincerely. Alan Schuster, 2/16/2005
We have a perfect pool! Thanks for
Todd G., 2/26/2005
► Dense Foam
From Soap Residual?
About 2 weeks ago I washed my pool
filter with simple green soap. Although, I thought I rinsed
thoroughly, small patches of foam appeared and the inlet
water is cloudy. I have added water and algaecide, but it
only got worse. I tried shocking the pool and adding
clarifier, with no results. I have scooped a lot of foam out
of the pool but it keeps foaming. I was told to put in a new
filter, however, the soap appears to be in the water in
probably no longer in the filter. I live in Florida with a
high water table so draining is tricky. Any suggestions
would be appreciated. The local pool store is without
answers. Thank you.
Mike K., Florida, 4/24/2009
Shut off the pump and add a water hose to the bottom of the
pool. Add water, until the pool overflows. That could take
much of the problem out of the pool. Add a dose of an enzyme
treatment to help decompose any remaining soap. Use some spa
antifoam, if still needed. Good luck.
Alan Schuster, 4/24/2009
Hi Alan. Tried the water hose with the
pump off. It appears to greatly solve my problem. Thank you
for the advice and the prompt reply.
Mike K., Florida, 4/25/2009
My pool has some sticky, oily deposits
around the water and in the skimmer. I think I know what it
is. I try to keep the use of sun lotions to a minimum, if I
plan on going into the water. The kids - that's another
matter. Any suggestions?
Marla S., Catskill, NY, 6/23/2005
You are probably correct that excessive use of oily sun tan
products could have lead to the deposits. Chemical
byproducts can react with these residues, as well as wastes,
debris and contamination, causing a problem with "scum"
deposits. Various pool cleaning products are available to
help clean the water line areas. The best products are those
that are formulated so as not to cause pool water foaming.
Some of the cleaning products use enzymes to help with the
removal. In addition, there are enzyme products that can be
added directly to the water and will help digest and
decompose oily, organic residues. Good luck. Enjoy the
Sincerely. Alan Schuster, 6/23/2005
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