Rebar Spots appear as rust stains on a pool/spa surface that grow over a period of time, and are more than surface deep. Unlike rust that forms when iron “falls into” the pool, (As with bobby pins, nails, lawn fertilizer with iron, ….) these stains are stationary, only on horizontal surfaces and are more than surface deep.

Note: Sometimes rebar spots are confused with black algae.

Note: Unlike Rebar spots, Black Algae will form as numerous small spots over an area of the pool, and can be scrapped off. Scraping rebar spots only reveals more, and deeper, rust.

What are 'Rebar Spots'? 

            Rebar spots are rust stains. They are formed when water from the pool seeps through tiny fissures or cracks in pool's surface, and it reaches the metal framework in the lower layer of gunnite (Bottom layer of Concrete). When it does, the steel rebar rusts, and this rust seeps back up through the structure to the surface forming a rust stain.

  Where are 'Rebar Spots' Found?

            Rebar spots are most often found on plaster(Marcite) pools, but can also be Found on other types of in ground pools utilizing 'rebar' in the internal structure of the pool. 'Rebar Spots' can be found on any surface of pools with this type of internal structure: Walls, Steps, Floor, Love Seats ...

Whose fault is it?

            Rebar spots are caused by having insufficient, or damaged gunnite/concrete material over the rebar framework. This is NEVER a water chemistry issue, and thus NEVER the fault of the home owner or the service technician. Any steel in contact with water will rust. Water chemistry can never, in a pool environment, cause this. Just having any moisture reaching the steel rebar will cause it. You could never fill the pool with water, never put one chemical in the pool, and if the area got wet, it will still cause a rebar spot.


Solutions for 'Rebar Spots:'

            Rebar spots can be chiseled out of existing surfaces and a patch can be applied. That said, if you have more than two rebar spots, save your money for resurfacing as your problem is probably chronic, and you will probably get a new rebar spot each year until you do resurface. Assuming that you only have one or two rebar spots, finding someone who is willing to put in the effort to do a “proper job” with the repair, is going to be difficult. What needs to be done is:

                    1.) chisel down to the rebar and locate where it is rusting. Note: this could be a foot away from where the stain actually comes to the surface.

                    2.) Chisel back along the rebar you just exposed, until you locate un-rusted rebar on all ends. Note: Since rebar is laid out in grids, often the rust can transfer to crossing rebar sections. In most cases, this repair can be done in less than a one foot area. If it exceeds one foot, I notify the customer, and stop at this point, unless the customer authorizes me to go further (at greater expense). (Anything beyond 2’ diameter I consider to be unrepairable, I cut out the rebar I can see, and proceed as follows.).  

           3.) Regardless, I cut out all rebar about a 1/4 inch from each of the edges in the opening, and square up the hole. I put epoxy putty around the ends of the cut rebar and pack it tight, and then prepare the patch. NOTE: YOU WILL NEVER match the surfaces. The best you can get is close. Also, there is no guarantee that the spot won't reappear inches from where each patch was applied, but reoccurrence, when this method is followed “exactly”, and all the rusted rebar is completely removed, is rare.

        Note: Unfortunately, most companies are nowhere near this thorough when they treat rebar spots. They cut a small section away, or chisel it away and put patching material in. Few cut out 'ANY' Rebar, and fewer still seek to follow it back to unrusted rebar. Get them to explain the process they use, before accepting them as your repairman for this job. You might want to tell them, up front, that you would like to see the rebar when they are finished so that you can check to be sure that they cut out all of the rust. There should be a shiny new end, without rust, and an end pretty much eaten away by rust, on all pieces cut out.