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Thread: Acid Wash

  1. #1
    Join Date
    Dec 1969

    Default Acid Wash

    Hello old gang! Plaster is now 5 years old and we have several stains as well as some calcium formations, rough floor etc. I found this proceedure on another site. Any glaring mistakes? I plan on using 38 cent/pound Walmart baking soda to adjust pH of wash water at bottom of pool, add 2 boxes between every mixture of acid I use.

    Tha Beerman!

    Also called a drain & clean, an acid wash becomes necessary if the pool has turned into the "black lagoon". This may occur if the winterizing process is not done properly, or if the pool has been stagnant for a period of time so that algae have taken over. If you notice scaly, man-phibian creatures splashing around out back, it's probably time to drain & clean.
    Our general rule of thumb for determining the need for an acid wash is: if you can see the bottom of the pool (the floor) then you can bring it back with chemicals, labor and filtering. If the floor is not visible, the cost of the chemicals and labor will generally be greater than the acid wash charge, and take much, much longer. Also, extensive algae blooms will stain plastered pools, making an acid wash desirable.
    An acid wash is, put simply, purposeful stripping of a tiny layer of plaster, exposing fresh plaster beneath. Therefore, it is ill-advised to make it an annual custom, which will accelerate the need for replastering. Most plaster coats (sometimes called whitecoat or marcite) are in excess of 1/2", so a few careful acid washes should not hurt. Pools can also be bleach washed, pressure washed or treated with citric acid.
    You may also decide on an acid wash not because of swamp conditions, but just to bring out a brighter, whiter finish. Mineral stains and/or deposits, chlorine stains, even dirt stains...an acid wash is always a dramatic aesthetic improvement.
    If your pool has had years of algae blooms, and if your pool seems to grow algae overnight or just bloom very easily....changing the water and acid washing the surfaces algae sticks to can give you an algae free summer.
    Acid is a dangerous substance. Pool company personnel are specially trained in its application and wear protective clothing and breathing apparatus during the acid wash. To protect our environment, the acid/water waste should be neutralized with soda ash prior to its being pumped to a safe location.
    If you decide to drain and clean your own pool, make sure that the hydrostatic relief plugs are pulled as soon as possible, and that the water is pumped to a distant location, or into a storm drain. You may also need to check with local water authorities for waste water discharge regulations.
    As you drain the pool, wash it down (scrub if necessary) to remove all algae and leaves. Bag up all leaves and debris in the pool's bottom. When the pool is clean and empty, you can begin to acid wash the plaster. Put on protective clothing and rubber boots, goggles and wear a breathing mask designed for acid fumes.
    Add 1 gallon acid to 1 gallon water in a flower watering can (Always add acid to water, never the other way around). Wet down the wall with a hose. Keep the hose(s) running at all times, without a nozzle on it. Pour the acid/water mixture down the wall, from top to bottom, one 10 foot section at a time. Do not allow the acid to sit on the plaster for very long. Usually 30 seconds is long enough. Use an acid brush to scrub the surfaces and move the acid around. Rinse quickly and thoroughly. Make sure acid is rinsed completely, as it will continue to etch the plaster. Also try to prevent the acid from wearing a channel path from shallow end to deep end. This can create a worn stripe on the floor.
    If the 50/50 mixture isn't strong enough, you can increase the acid strength or the hang time (before rinsing), or scrub harder. Usually pools are acid washed twice with the same strength mixture. Remember that you don't want to damage or "burn" the plaster.
    After the acid wash, the bottom of the pool will be filled with a foamy, acid puddle. This needs to be neutralized before pumping out. Use 2 lbs of soda ash per 1 gallon of acid used. Broadcast the ash over the puddle while stirring with a pool brush on a pole. Use a small submersible pump with a hose to pump out the remaining acid water. Be careful where you pump it to. Even if properly neutralized, it may destroy plants or kill fish, frogs, etc. Rinse the bowl again, and repour the bowl of the deep end to clean up well around the drain, being careful not to burn the plaster too much.
    Don't rush the job and be safe. The fumes can be very strong. And very dangerous. Be sure to wear a respirator that will block muriatic acid fumes, goggles or safety glasses and protective clothing. Wear old shoes, or rubber boots. Spray off before exiting the pool. Transporting the acid from the store to the house can be hazardous also. Secure the load in the vehicle. Always have a second person nearby when acid washing the pool. If acid drops enter the mouth or eye, rinse with the hose for 15 mins, without a nozzle on it. Acid on the skin won't usually burn too much, just rinse quickly, for 30 seconds.
    It is advised that you pay a service com"

  2. #2
    Join Date
    Dec 1969

    Default Re: Acid Wash

    Just bumping this to the top, plan on pumping down pool overnight, doing the acid thing in the morning and get her filling back up ASAP!


  3. #3
    Join Date
    Apr 2006
    St. Joe, MO

    Default Re: Acid Wash

    I'm interested in this subject. I would say that the procedure is sound, and I should be able to DIY (assuming I can be careful enough with the acid -- muriatic fumes are bad news, plus if you are down in the pool you are in a confined space and I would expect the fumes to hang around in the pool's tank or depression).

    But riddle me this: before I can attempt an acid wash I have a whole lot of leaves to get out - the pool has been completely neglected for at least a couple of years before we bought the property -- will a diaphragm pump take out leaves with the water? It seems to me that one should be capable of doing so as long as we can keep the hoses open and flowing.

    Please mark this URGENT! (I have received great help and wise counsel from this forum in the past, I hope you can come through again. Thanks)

  4. #4
    waste is offline PF Support Team Whizbang Spinner waste 3 stars waste 3 stars waste 3 stars
    Join Date
    Dec 1969
    S.E Maine

    Exclamation Re: Acid Wash

    I just want to make sure anyone acidwashing their pool remembers the possibility of the pool floating while its empty!! If you've recently had torrential rains or had a lot of snow this winter that's just recently melted away... wait to drain the pool until the ground has had a chance to absorb all the water (your hydrostatic valve may or may not let enough ground water through to keep the pool in the ground!)
    Luv & Luk, Ted

    Having done construction and service for 4 pool companies in 4 states starting in 1988, what I know about pools could fill a couple of books - what I don't know could fill libraries

  5. #5
    waterbear's Avatar
    waterbear is offline Lifetime Member Sniggle Mechanic waterbear 4 stars waterbear 4 stars waterbear 4 stars waterbear 4 stars
    Join Date
    Nov 2004
    St. Augustine, Fl

    Default Re: Acid Wash

    The baking soda is not going to be as effective as soda ash in neutralizing the acid. I would not recommend it. You can use borax at about twice the amount of soda ash needed if you want but the soda ash should be less expensive (if you buy a 50 lb bag from the pool supply. It should be around $25-$35 in most areas.) Trying to save a few pennies here could cost you a replaster job in the end!
    Last edited by waterbear; 03-19-2009 at 12:55 PM.
    Retired pool store and commercial pool maintenance guy.

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