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Thread: Crumbling mortar or grout at waterline tile

  1. Back To Top    #1

    Join Date
    May 2010
    Palm Springs area, CA

    Crumbling mortar or grout at waterline tile

    I have an older pool, probably 12-15 yrs old or so, at the house I moved into several years ago. At that time it had been neglected somewhat. Unfortunately the condition of the mortar (I assume by appearance-see pics below) at the waterline and in some cases below the waterline was invaded by blue green algae and over the years vigorous scrubbing along with deterioration from the algae has thinned it out. It became quite "crumbly" and junky in some areas. At this point there are a few areas where the mortar has completely worn away exposing what I assume is the gunite underneath. I'm particularly concerned with areas where this is below the waterline.

    1)My first question is can I go and buy regular old mortar at Home Depot and patch these areas? If that's not practical what are other options, eg polyurethane caulk, pool putty epoxy, etc. I can't afford to retile the entire waterline right now so I'm looking for the "quick fix" but I want to do it the right way if possible. I'd like to mortar it and will lower the water level to below the worn areas. This does not appear to be typical pool grout - please correct me if I'm wrong.

    2)Second, I have a tile on the waterfall that has been missing since I moved in. I have a tile saw and I did finally find the right kind and thickness of stone to cut a replacement (I have a tile saw - hoping it will cut stone and have done some minor house tile jobs). I would also like to mortar around the new tile. Thinset necessary?

    3)Obviously I've really accumulated some calcium buildup at the waterline recently. My ph has been 7.4 to 7.5 and my CH has been on the low side around 200-230, so I'm not sure why that is happening. Will dilute muriatic acid on a sponge or spray bottle work on that?

    Here are some pics.

    P1010951.jpg Photo by desertjon74 | Photobucket
    P1010948.jpg Photo by desertjon74 | Photobucket
    P1010947.jpg Photo by desertjon74 | Photobucket
    11,000 gallon in-ground pool/spa combo, pebble-tec, Sta-rite system 3 cartridge 300 sqft, Pentair Whisperflo WFDS-6 2 speed 1.5 HP full-rated, formerly Starite Max-e-Glas 2 HP up-rated single speed, Sta-Rite Max-E Therm natural gas heater. Jandy Aqualink RS Onetouch. Manual vacuum. Chlorine.

  2. Back To Top    #2
    Mod Squad pooldv's Avatar
    Join Date
    Aug 2012
    DFW, TX

    Re: Crumbling mortar or grout at waterline tile

    1. You can use regular old mortar or grout. But it would be easier to use two part pool putty, get black and white and mix them to match the gray. It can be pushed into the joint and will cure underwater.

    2. Stick the tile there with whatever is handy, silicone caulk, polyurethane caulk, mastic, thinset. Use the epoxy above.

    3. Keep your CSI between -0.1 and -0.3 to prevent this. Poolmath will give you your CSI number after you enter all the results. Tweak PH, TA and/or CH to change the number.

    More here, Pool School - Calcium Scaling
    And here, Langelier and Calcite Saturation Indices (LSI and CSI)
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