The grout in your pool is not only a structural necessity to keep the water from leaking out through the tiles, but, when clean, gives your pool a fresh and appealing look. So whether you have a leak or your grout has just got dirty over the years, you may find that you want to regrout the tiles. You can do this yourself and save a lot of money. It is a simple, straight forward task, but quite time consuming, so leave plenty of time to work before you want to use your pool again.
Drain the pool using a sump pump. This will take some time, especially if your pool is full, so start several days before you want to regrout.
Put on goggles and respiratory mask to protect your eyes and keep from breathing in the dust from the grout.
Use a narrow grinder with a diamond bit to grind out the old grout between each tile. Grind at least a ½-inch deep channel or the grout won't stick.
Hose out the cleaned channels to remove any dust you created while grinding. You should do this right before you apply the grout so the walls are still wet.
Prepare the pool grout according to the directions on the package. Only prepare a small amount at a time to avoid it drying out before you can get it on the tiles.
Spread the grout into the channels between the tiles with a putty knife, making sure the grout gets pressed in all the way. Don't worry if some grout gets onto the tiles. Fill all of the channels with grout and let it set for one or two hours.
Wipe down the surface of the tiles with a wet sponge to remove any grout. Be gentle, because the grout will still be soft.
Let the grout cure for at least 24 hours and scrub the tiles with a brush. This will remove any slight traces of residue on the tiles and get rid of excess grout.
Do grout repairs in the spring when the weather is pleasant and the water level in your pool is at its lowest so you will avoid wasting more water than necessary.
Do not use power tools near water or while you are in the water.