Two pool questions: What "mortar" or "grout" to use; and how to get rid of green (algae?) spots?

[Elmo]

I have two questions about pools.

1. About six to ten inches of mortar are missing from the top corner of an edge of the tiles at the top of the pool. These tiles get wet but this particular edge is about two inches above the water line.

What grout (mortar?) is used for edges where horizontal tiles meet vertical tiles near water?

1. I have green spots that seem to be spreading on the walls of the gunnite pool, in the deeper areas. The water chemistry, as checked by Leslie's Pool Supply, seems ok (they said the chlorine is perfect, the pH is perfect, the Calcium is fine, the total dissolved solids are very low, and the Phosphates are a tad on the high side.

I assume it's algae (but how would I know)? I shock with three pounds of chlorine (35,000 gallon pool) about once every two or three weeks.

I've been scrubbing the green growth off but is there an easier way to identify and then remove whatever it is that is causing green growth in tiny spots (about the size of a pencil width) on the gunnite walls?

[Steve B]

I fought those, then bought this thing that looks like one of those pencil erasers you would slide over your regular pencil eraser. You put it on the end of a pole, or you swim down and rub the spots. It worked pretty good. It's sacrificial, it is like rubbery, and it rubs off the eraser before it eats off the concrete. Algae is easier to prevent than cure. At times, I have taken the power washer hose in there BUT YOU HAVE TO BE CAREFUL AND NOT BLOW THE CONCRETE AWAY.

Steve

visit my blog at

[DD_BobK]

Stuff that grows in pools (& other places, like cooling systems) create what's called biofilm to protect the colony from adverse effects of the environment.

Brush at reasonable intervals (not every day but more than a couple times per week) tol damage the biolflim so that the chlorine can get at the algae. Consider a pool sweep style machine with whip hoses that have plastic or ceramic wear points.

Also consider the use of a specific algaeicide for green algae.

cheers Bob

[dadiOH]

How thick?

If thin (to 1/2" or so), thinset is fine.

If thicker, any standard mortar, Type S is a tad stronger.

Or, a mastic caulk might be better if the joint is subject to cracking. Polyurethane caulk is very good (but messy to apply smoothly).

[ransley]

I dont have pool experiance but for concrete and painting mold must be completely killed and removed or it will ruin and bond of new mortar, anything not killed will return and ruin mortars bond. Chlorine should kill it quickly then powerwashing should get rid of the plant. Do you pay someone to test the pool, It should not be hard or expensive to do it yourself.

[gpsman]

For something that small I'd use a marine sealant (caulk). Back in the olden days we just used a sanded grout, but today there are expoxy grouts that are probably better.

There's your problem. Phosphates are algae food. You need a phosphate eliminator like Phosfree. Comes with phosphate test kit.

I shock my 20K gallon pool every week (2#), but our dog spends more time in the pool than anyone.

Automatic pool cleaner, but I'd recommend not a Kreepy Krawly.

I'm no pool expert but I think you probably ought to learn to do your water chemistry yourself. Only takes a few minutes a day. -----

- gpsman

[Elmo]

The thickness is about 3/8ths of an inch between the horizontal and vertical tiles.

I have a huge bag of "thinset" (because it's the smallest they had to repair just one tile on the BBQ) ... but I wasn't sure if pools (since they're always wet) took a different mortar/grout???

[Elmo]

I test it myself every few days and once a month I bring a sample to the pool store for detailed analysis. The phosphates are a tad high but the chlorine is dead on correct (at 4ppm).

I have a power washer (which wasn't meant for underwater use) which I might try. Plus I might have to buy the very expensive algaeside and/or phosphate reducers.

I wonder which is better in the long run:

- Killing the algae (it will come back) ...

- Removing the phosphate (it will come back too) ...

Any experience to share?

[JimT]

Yeah....pool supply places like to test your water so they can sell you stuff. Some of it isn't really needed.

On the algae I've always kept the chlorine in check, shock weekly and scrub, but there maybe some product that keeps it down effectively. Regular pool cleaning usuually does the trick. I'm havng trouble with black algae but that's because my pool is old and pitted. That stuff is a bit@h to get off.

I'd use swimming pool grout for your tiles, but like has already been mentioned, get all the algae off first. At the close of this season I'm getting a Dremel to cut all the bad grout out.

[Oren]

HD sells a small container of grout, meant for pools. I think it is both adhesive and grout. Located in the tile section.

I replaced a few tiles about four years ago and it is still holding up. The product cures under water.

[dadiOH]

It will work. Showers are wet too.

[dadiOH]

Algae love phosphates.

[JimT]

That's probably what I need to test. Does it apply to black algae too?