Marble dust

[mhostage]

My pool maintenance company is recommending that I have them do a "marble dust" treatment. They want to charge me about $6,000 for the work and I'm trying to find out more about the subject. My pool is 20 years old, gunnite, 20 x 40, not heated. I'd appreciate some informed advice. Thanks. I'm 76 years old, not very web savvy and, if possible, a reply to my emaIL address would be appreciated (mhostage@aol.com).

[czechmate]

I brief check of search engine, there is no reference of a marble dust as a common name of any plaster application. Neither did I ever heard of such a reference.
They may be talking about marcite, a crushed marble, the most common plaster substance for white plaster job.This is also the cheapest, fairly obsolete and algae prone surface.
(It is often used as a bait and switch or get the foot in the door technique by some contractors).
Here is what you can do for yourself:
Find a plaster and tile wholesaler and if possible visit them in person.
There you will see all late available modern pool surface samples available in the pool industry.
It is also pretty good place to get a recommendation for a reliable re-plaster contractor.
Never use pool servicing company to contract a re-plaster.
You do not need pay a middle man 500 bucks for arranging this work.
Instead, you can use this saved money to upgrade the type of material used.
I will be happy to answer any specific questions that you may have in the future regarding resurfacing the pool.
I am sure, that there is lot of pool owners here, with experience and advice on different pool surfaces willing to share some information.

[tallyman1]

18x36 gunite pool, built 1976, marcite plaster (marble dust and white portland mix commonly used at that time), surface is moderately pitted, rough, calcium scaling, otherwise in good shape, no leaks. Question: after acid washing to remove the calcium, followed by rubbing the surface smooth with a hand-stone, is it a good idea to use a clear concrete sealer on the marcite surface? If so, what type of sealer? Acrylic? (Evidently this is not a common practice based on my internet search). Thanks in advance for your comments.

[czechmate]

18x36 gunite pool, built 1976, marcite plaster (marble dust and white portland mix commonly used at that time), surface is moderately pitted, rough, calcium scaling, otherwise in good shape, no leaks. Question: after acid washing to remove the calcium, followed by rubbing the surface smooth with a hand-stone, is it a good idea to use a clear concrete sealer on the marcite surface? If so, what type of sealer? Acrylic? (Evidently this is not a common practice based on my internet search). Thanks in advance for your comments.

Marcite plaster this old is most likely a candidate for re-plaster.
Actually was for a few years.
There is no way any pumice stone rubbing will make this old plaster smooth. The plaster is disintegrating and starts harboring algae. Do not fool yourself and do not listen to your pool handyman either.
You will waist your time and money without a result. You also have easily 500 sq feet area!!
Consider re-plastering instead. Price tag: 3000- 5000 depending on state and type of plaster.
In 5 years, the savings on the algaecide and supershocking will reimburse half the cost.

[tallyman2]

I hear what you're saying. The quote I got for resurfacing was $8,500. That's high I know, but the contractor said he puts a lot of manual labor into chiseling and surface preparation. His crew chisels out adjacent rows that go all the way down to the gunite. I've heard there can be huge problems with poor bonding of the new surface regardless of how much surface preparation is done.

Again, the question I have concerns whether it is a good practice to use a clear sealer if I decide against resurfacing. Any comments on the use of a sealer would be appreciated.

[czechmate]

Chemgeek may correct me, but I am fairly sure, there is no sealer for a marcite plaster that would for one, bond an hold on deteriorating plaster and for two, withstand the chemicals in the water.
Common sealers used on travertine, marble, granite, etc are silicone based. In an outdoor application it will last one season. I do not believe it is developed for a submerged application.
Chiseling is not necessary for resurfacing, though it may pad up a paycheck real well.
Go to the web and find pdf version of Diamond Brite application as well as Bond Kote preparation of surface.
It will give you an idea about modern materials an manufacturers approved application.
Also some of it, like the "preparation", you may do yourself and save money.
Any detail you need to clear, just ask, I will try to answer.

[tallyman3]

Your sealer comments make a lot of sense. Looks like there isn't any clear compound that has been developed so far that will perform under water as a marcite sealer. That apparently leaves the various epoxy or rubberized paints as the only options for sealing an older acid-washed marcite surface. I certainly want to avoid painting if I can. Concerning your comments about chiseling, etc., the contractor told me that the resurfacing won't last if the chiseling isn't done. He bases that on 30+ years of experience in this town. His $8,500 quote was based on using DIAMOND BRITE aggregate which he guarantees for 5 years. He says that if the chiseling isn't done, 'blisters' and other problems will occur, so I tend to believe what he says based on his excellent reputation. But, really, I don't see what would be wrong with trying to get another few years out of the existing surface since it looks OK and isn't leaking. About rubbing the surface smooth with a pumice stone, I was only going to do that on the entrance steps and a few of the roughest spots on the floor. What about using a drywaller's sanding pole with coarse grit sandpaper on the walls and floor -- not to achieve absolute smoothness but just to knock down the 'stalactites' a bit?

[czechmate]

Assumption how certain tools would work is useless, until you actually see the surface after draining and drying the pool. I suspect that the surface will be structurally similar to a old sandstone like surface like you see around lakes.
Your approach would resemble pumping a flat tire twice a day instead of having it fixed.
Except your pumping will not be free.
I respect the 30+ years of experience of your pool contractor.
I also respect the tremendous progress of the pool industry in the last 25 years.
Thousands of people use have their pool resurfaced annually.
When done properly, the lifespan is about 10-12 years.
300-400 a year is worth it, considering your savings in chemicals, frustration, total appearance, etc.
Do some reading in this area, you will be surprised what is available.
BTW, I would not paint my pool if it was offered for free.

[tallyman4]

Thanks again for taking time to provide comments. Well, the pool has been drained and has been dry for about ten days. I have been experimenting with various sanding techniques and have concluded that the drywallers' sanding pole with 20-grit sandpaper will smooth the surface enough to reduce the formation of algae compared to what it might be otherwise. (Takes a lot of sandpaper, though). Rather than wash down the fines to the drain with a hose, I've decided to use a shopvac to vacuum the dust so that it won't collect in the drain line. The flow velocity through the bottom drain won't likely be fast enough to prevent all that sand and marble dust from building up in the drain pipe. For the few spots that need patching, I ordered some 'marcite pool mix' from a plaster supplier and plan to 'smear it' over the top of the biscuit-sized two-part white epoxy patching compound that will fill in the few 1/2-deep holes that I have. I figure the total cost of my sanding and patchup approach will save me about $7,800 relative to the $8,500 quote I got. Then, if my 'grand scheme' doesn't work, I can do it the right way in another year or two (maybe three?).

[czechmate]

I assume you have your hydrostatic plug removed, which is crucial.
Water under the pool will give you about 1-1 1/2 feet of deep pudle to place your portable pump.
The pump usually needs 24" and will let you know when it is starving. You need 3 -10ft schedule 40PVC, 1-90, 1-male fitting, 1 coupling and go to town. You can use it for a light acid wash as well.
You buy a nice pump for about 60 bucks and keep it or sell it as barely used on craigslist for 40.00.
I would not bother with a shop vac. Once you done with sanding, you will need absolutely dust free surface to apply plaster. So you will either pressure wash or just hose down under pressure and let dry up.
We all search how to save a buck and I am just like you.
Just trust me with the portable pump. Best 60 bucks you will spend this year.
Good luck!!

[decorative concrete]

polyaspartic sealer

[czechmate]

This is not a Jeopardy show, it is a pool forum.
BTW, the thread is 1 1/2 years old.