Plaster issues: Discoloration of Diamond Brite Midnight Blue

[arvpoolnj]

Hi everyone, I am a first time poster here at TFP, but have been reading about water chemistry for a couple of years here. Our pool was renovated in the summer of 2017. It was resurfaced with Diamond Brite Midnight blue. Starting towards the middle of last summer we started noticing discoloration of the surface.

This spring when I re-opened, it seems to have spread more. I called my contractor and he believes that it is calcium scaling/nodules. We do have very hard water in this area. PC recommends "hot start"ing the pool, i.e 4 days of sub-6 Ph. He believes this will remove the discoloration. I wanted to get a 2nd opinion by posting here as it also seems similar to the white

I generally succeed at having my pool chemistry in check, never had a green pool. Current readings are:

27K Gallon, in-ground plaster pool.
Calcium Hardness: 280
Ph: 7.5
CL: 2 (working on raising this now after the open)
CYA: 90
TA: 150 (working on dropping this a bit with aeration and lower Ph)

I have posted images. Before making a decision to do the hot start, Id like to get an opinions as to whether this is really the issue especially since my calcium readings dont seem that high to me? Any help is appreciated, especially from OnBalance who seems to have written a lot on the subject of plaster issues.

 

[ajw22]

Welcome to TFP.

Calcium scale comes from high CSI, it does not need high CH. Unfortunately water pH often rises during the winter when the pool is closed. My water pH was around 8.8 when I opened my pool last month. That high pH raises the CSI into the scaling area.

Do you have a heater? Do you have a heater bypass to protect the heater while your pH is so low?

When I had a scale problem we did the 4 day acid treatment, then drained the pool, did a diamond polish of the plaster, then a refill from water trucks. You can read about my problems here --> Replastering a Pool - A 1 Year Saga - Problems & Lessons Learned

We can see if @onBalance has any thoughts.

 

[onBalance]

l can see that there is some white spotting and streaking, but it is hard to tell how bad, or how wide spread it is or isn't.
My write-up "White Spotting in Pools" will explain what may be happening in your pool. You might want to share that article with the contractor.

It doesn't look like calcium scaling or nodules, but a simple "spot" acid treatment or sanding a small area will tell the tell. Scale will come off easily with either treatment.
If the problem isn't scaling, then the "hot start" acid treatment will not remove the white discoloration.

White Spotting of New Plaster Pools

 

[arvpoolnj]

Hi, thanks for your comments on this thread, I really appreciate it. The main question I have is, is there a way to test, without draining the pool if this is:

- calcium scaling (removable by hot-start etc)
- consequences of poor plastering (from the white spotting thread, it looks quite different)

I do have some updated information.

- Fill water CH: 230
- Current pool CH: 330
- TA: 110, Ph: 7.2
- I have not been using an calcium de-scaling products in the past season and did not do treatments over the winter.

When we re-opened, after the winter, we see much more extensive spread of these white splotches. The pool is filled and I am really trying to avoid any solution that requires draining and refilling (since its not that bad, the pool generally still looks blue).

The PC is suggesting (since we do have a heater bypass):
- doing the hot-start treatment, which is dropping the Ph down very low (to about 6) for 4 days
- then slowly bringing the chemicals back up
- PC believe this should address all the staining
- from that point adding weekly calcium stain and scale remover

 

[onBalance]

Try using a small plastic bottle that you can squeeze the acid out onto a small whitened area and see if it darker immediately. If not, then I doubt that it is calcium scaling. There isn't a practical or simple way to test for the white spotting problem that I have written about.

The Hot Start treatment will remove calcium scaling, but not white spotting (from improper plastering techniques). It will also etch and age the plaster surface. So if that treatment doesn't remove the whitened areas, you are left with a less than new and smooth surface.