After 3 years of battling a pool that looked milky/cloudy (with occasional pink slime) no matter what I did, I finally solved the problem.
All of my chemicals have been balanced. Pool has been vacuumed regularly. Filter chemically cleaned regularly. DE changed regularly. Surfaces brushed to prevent any slimy build up. I used floc. I added liquid clarifier. Despite all of this, the pool still had a whitish haze to it. My expensive pump and filter was telling me that I needed to backwash within 3 days of cleaning the DE off the grids and adding new DE, and the "intelligent" pump was running at 4 times normal power. I was ready to just drain my 30,000 gallon pool and start over. Thankfully I didn't.
The problem was white water mold. White water mold is NOT algae (plant). It's a biofilm (animal) that attaches itself anywhere there isn't sunlight, especially in skimmer areas, behind pool lights, beneath ladders, and MOST IMPORTANTLY, IN THE PLUMBING. Classic symptoms are a slimy coating on these areas and tissue like substances floating in the pool, which when broken up make the pool cloudy white. The real culprit is water mold in the PVC pipes. It grows, bits get broken off as water moves through the pipes, and the bits end up in the pool. Even if you have gotten rid of all slimy surfaces that you can reach, you will still have a cloudy pool if you don't get the mold out of the pipes.
Here's how I got rid of my mold problem.
1. Remove your pool light (don't forget to shut off the breaker!) and clean the light (meaning take it completely apart and wash it thoroughly). Just use anything that will kill bacteria except cholorine. You can use a diluted mixture of water and shock. Let the parts sit in the sun for a few hours. This will both dry the parts and the UV light will help kill any residual mold.
2. Remove your ladder and wash it thoroughly, paying close attention to the areas under the steps. I used a power washer to really get the stuff out. Let it sit in the sun as well. Remove the eyeballs from your return lines, clean them, and let them soak in water and shock. Leave them in the sun.
3. Remove the top to the skimmer, take out the basket, and thoroughly brush/scrub everything, including the back of the flapper. Use your fingers if you have to. Keep doing it until you cannot feel any slimy surfaces. Clean the baskets thoroughly with a high pressure sprayer. I also recommend soaking it in a solution of shock and water and then letting it sit in the sunlight.
4. Open the cover in your pump, remove the basket, and brush/scrub the area under the basket. Clean the basket with a high pressure spray, soak it in water with shock, and let it sit in the sun.
5. Give your pool a good brush and make sure you get the "detail" areas like the place where the skimmer meets the side of the pool and the outline of the steps. You want to make sure you have slime-free surfaces.
6. Open your filter, remove all removable parts like DE grids and cartridges and clean every inch of the filter with a high pressure spray and scrub the thing as best you can. You need to get every inch of it. I actually detached mine from the pipes so I could access everything. I have DE and I sprayed all the DE off the grids and soaked the grids overnight in a bath of water and shock. I let them sit in the sun for 4 hours as well.
7. With the filter detached, shoot high pressure spray into your valves and pipes...whatever you can reach.
8. Reassemble your filter and add DE, sand, etc.
The next step may be dangerous, so please consult a pool professional.
9. Now it is time to get the mold out of your pipes. To do so, you need to isolate each pipe. Let's say you have a bottom drain, two skimmers, and two returns. That means you have 3 "input" lines and 2 "output" lines. Set your valve to recirculate/filter bypass. If you don't have this feature, it's OK to have the water run through the filter. Put on eye protection, gloves, and protective clothing because you will be working with shock.
10. First, let's tackle the main drain. Mix 1/2 gallon shock with 1/2 gallon of water. This is a very concentrated mix, so be very careful. You need to get that mixture down the main drain pipe and let it sit for 5 mins. How you get it down depends on your plumbing. I unscrewed the top of a diverter valve and poured the mixture down the pipe. If you hear lots of bubbling, it means that the shock has come into contact with the mold and is scrubbing it off your pipes. Let the shock sit for 5 minutes. Make sure your diverter valve is set so that intake is coming only from the main drain. Crank up your pump to as high as it will safely go. I have a Pentair Intelliflo VF and I set the flow to 60 GPM. Let it run for 5 minutes. You want as high a flow as possible to dislodge the mold from the surface of the pipes. Shut off the pump.
11. Next, block off one of your return lines. I had to unscrew the eyeballs and put in the winterizing plug. Block off one of your skimmers. I had to screw in the winterizing plug to do this as well. This will isolate one of your skimmer lines and one of your return lines. Make sure your diverter valve is set to the skimmers. Get the pump going as high as safely possible. Now, SLOWLY...and I mean SLOWLY...add shock directly to the skimmer. Start with just a cup to see what will happen. If you have water mold in the pipes, the shock will instantly react with it and you will see bubbles in your pump basket and out through the return line. You should also start seeing tissue-like bits and pieces in the water. Keep adding shock until the bottle is gone. Let it run for at least 5 minutes...make sure it is not bubbling anymore.
12. Repeat for the other skimmer and return line.
13. Open all returns and skimmers and reinstall the eyeballs on the return lines. Keep your diverter valve set to the skimmers. Change valve setting from recirculate to filter (if you don't have a multiport valve, skip this step). Start the filter at a normal flow. Pour 1/2 gallon of shock into each skimmer SLOWLY. This time, we are running shock to the filter to make sure we kill any residual mold in the valve and nooks and crannies of the filter hardware.
14. At this point, you should see a bunch of white stuff floating in your pool and your pool should look even more cloudy than it was. Congrats, you have gotten the mold out of your lines and it's now in your pool. Now you need to make sure it is dead. Add shock to your pool so that you have a double dose (make sure you take into account the shock you put into the lines).
15. Doublecheck your water chemistry. Make sure everything is balanced and that you have a normal sanitizer level.
16. Run your filter continuously until it clears up. It took me 48 hours. Depending on the filter media you use, you may need to add floc or DE as a filter aid if the pool is still cloudy. After it clears, it is a good idea to backwash and/or clean your filter media again.
My pool is now crystal clear and my variable speed pump is working exactly as it should (at 250 watts instead of 1500 watts). Good luck!