Removing Stains From Pool Plaster
SwimmingPoolSteve.com is user-supported. In order to keep this resource about pools and spas available for free to all readers I earn commissions for purchases made through links on this page. For more information see the full disclaimer page. By using this website you are agreeing to the terms and conditions.
Swimming pool plaster is a thin mortar application over the structural concrete shell of your swimming pool. Most commonly pool plaster is white, or a white base with colored aggregates or integral pigment added to the plaster mix. The end result is that most plaster is either white or light in color, and this can lead to potential staining issues. Other colors of pool plaster can stain just the same as white or lighter color plaster, but stains on white or light color plaster are going to be far more visible darker colors. This article will discuss some of the most common ways to fix stains on your pool plaster surfaces.
Before we get too far into the technical steps to fix stains in pool plaster you should first be aware that both very new and very old plaster are the most inclined to stain. Old plaster has become rough in texture and has lost a good portion of the cement component in the surface layer of the finish. This rougher surface is more inclined to accepts staining and it is also harder to clean away because the surface profile of the plaster is rough, not smooth. Very new plaster is extremely prone to staining due to the green mortar still curing and being highly absorbent. Any pool plasterer can tell you what happens if a leaf lands on new pool plaster and is not removed right away...it will leave a huge tannin stain which unfortunately is drawn deep into the plaster as opposed to existing only on the surface layer.
Right away if you have staining on your pool plaster you should be asking yourself if this is a result of your plaster being old and worn out. If the plaster is rough to the touch then you have reached the end of the service life of your plaster and you need to explore having the pool resurfaced. Yes, you can temporarily remove the staining by draining and acid washing the pool, a very common pool service, but in actuality this is counterproductive. If your plaster is already rough, this is the cause for the staining. Acid washing will remove some of the staining, but it will also make the plaster surface even rougher and more porous than it was before which guarantees the staining is going to come back even worse than before. Generally speaking, pool owners go to acid washing too often, usually as a result of service companies making the recommendation, but as a concrete pool builder I would strongly advise pool owners to avoid acid washing at all costs. A single acid wash of a pool plaster will reduce the smoothness and service life of the plaster by years. Definitely something you should want to avoid.
Treat metal stains with ascorbic acid - If you have iron or metal staining on your pool plaster surface this can look absolutely terrible, but there is some good news here. Usually there is not a silver bullet for problems but in this case there is. Vitamin C, or ascorbic acid, when applied to metal and iron stains will magically remove the stains right before your eyes. Depending on the nature of the stain you can rub vitamin C on the stain directly, or crush up the vitamin C and place it in a nylon stocking where you can sit it directly on top of the stain. Within an hour the stain should be gone or dramatically reduced.
Spot treatment with muriatic acid - Any stain removal that involves muriatic acid I am hesitant to recommend as per the above paragraph where I explain how it advances the age and roughness of the plaster. Still, a well established trick of the trade can be accomplished without draining the pool and using only a section of PVC pipe and some muriatic acid. Let's say you have a stain on the floor of a pool and you do not or can not drain the pool. In this case place some PVC pipe into the water such that it is covering the stain. Now pour a small amount of muriatic acid into the pipe. The acid is heavier than water and will sink to the bottom of the pipe...directly onto the stain. The strong acid solution will etch the surface to a small degree, but will also diffuse quickly into the rest of the pool water. This is not the best solution for every pool plaster stain, but still a great option available to you for certain specific circumstances.
Sanding out stains on pool plaster - If the stain on your pool plaster exists mostly on the surface then you should be able to remove a great deal of the stain with a very light sanding of the area. Using wet/dry sandpaper in the 220 to 400 grit range, lightly buff out the stains with a circular motion. This is especially effective for new stains which have only just happened and have not had a long period of time to soak down deeper into the plaster layer where sanding will be less effective.
Use a stain testing kit to determine the type of stain - There is a stain identification kit for swimming pool plaster which you can buy from the very popular "Jack's Magic" pool chemical company. This stain testing kit allows you to perform a few basic tests to see if you are able to remove or soften the stain. Depending on which test results in the stain reducing will determine what kind of stain that you have. This enables you to buy the correct stain removal chemicals for the exact type of stain that you have. This is one of the better options available to pool owners with plaster staining issues as the stain ID kit is very affordable and provides you with invaluable information you need to treat the problem properly. Here is a link to the Jack's Magic stain identification kit.
As a final potential option for cleaning stains from pool plaster, like in the event there is widespread staining to be resolved, I might suggest a chlorine wash of your pool. Similar to the acid washing process without being destructive to the pool plaster like acid washing, a chlorine wash will definitely help to reduce stains on your pool plaster. It might not be as visually compelling as acid washing, which certainly makes a pool plaster whiter and brighter, but any progress you make removing stains with chlorine washing will actually help resolve the problem as opposed to making the problem go away only to return in force a short while later like with acid washing.
Top content from www.SwimmingPoolSteve.com
Pool and spa chemistry crash course
New pool owner guide
The Swimming Pool Steve blog
Have a question - ask Steve
Swimming Pool Steve is an award winning, second generation swimming pool and spa specialist from Ontario Canada. With over 10,000,000 views on the Swimming Pool Steve YouTube Channel, winner of the 2018 Pool & Spa Industry Leadership award and author of hundreds of pool and spa articles both online and in print Steve is committed to helping pool and spa owners as well as pool and spa industry workers learn more about the technical side of building, renovating, repairing and maintaining all types of swimming pools and spas. Follow Swimming Pool Steve on Facebook, Twitter and YouTube.
Endorsed Brands From Swimming Pool Steve
The following links and products are to affiliates of the Swimming Pool Steve website. These are brands, products and services hand selected by Steve for endorsement. Please note that these endorsements can include monetary compensation, affiliate links and referral fees to Swimming Pool Steve, however there is zero additional cost to you should you use one of these products or services. Income generated from these links helps to keep this pool and spa resource available for everyone. To have your product or service considered for listing here as an endorsed brand email SwimmingPoolSteve@gmail.com.
Amazon Disclosure Statement - As an Amazon Associate I earn from qualifying purchases.
www.ClearComfort.com
Clear Comfort's patented hydroxyl-based advanced oxidation systems (AOP) represent the pinnacle of water care technology available to pool and spa owners. To put a complex technology simply, if you are looking for the best possible water care system for your pool or spa then you are looking for a Clear Comfort AOP system.
- Swimming Pool Steve
www.PoolPartsToGo.com
New Black + Decker variable speed pumps are available online from www.PoolPartsToGo.com and they are a drop in replacement for many popular pump models including Pentair Superflo and Hayward Super Pumps. With an adjustable platform base, union connections included and a very strong warranty these pumps offer an impressive value to pool owners.
- Swimming Pool Steve
www.PoolSupplyWarehouse.com
Pool Supply Warehouse has a large stock of swimming pool equipment, chemicals, maintenance items and consumables needed for caring for your swimming pool. They offer fast shipping and by shopping with this retailer you are helping to support Swimming Pool Steve directly.
- Swimming Pool Steve
www.PoolSuppliesCanada.ca
When it comes to ordering pool and spa supplies online in Canada www.PoolSuppliesCanada.ca is by far the best option. They carry everything from chemicals to replacement pumps to entire pool kits, with free shipping options and more "in stock" items than any other Canadian online retailer.
- Swimming Pool Steve