jack in oz

Thanks, the instructions on the container said either sprinkle on the surface or dissolve in warm water. I think I'll use the pantyhose method next time to be sure. Jack

My pool's surface is a blue cement-based render. I sprinkled 80g of dry CYA onto the surface of my pool 2 days ago. Most of it went straight to the bottom, so I spread it around with the pool brush. I thought I had broken up all the small clumps of powder, but today I noticed white spots in places on the bottom of the pool. Is it possible that some of the CYA powder has bleached the surface?

great thanks. It's a nice day for a swim, so I'll give it a try.

My two month old pool has developed a white crust in places on the grout. I assume it's a calcium compound. The grout is a simple sand & grey cement mix. In the past I have used muriatic acid diluted 10:1 with water to clean mortar off brick walls and I am wondering if the same mix will work here. I propose putting the diluted HCl in a spray bottle and applying it to the tiles then scrubbing with a stiff nylon brush. Before I proceed I want to make sure the HCl isn't going to convert the white stuff into some other compound that is even harder to remove. Can anyone help?

Thanks, I should have paid more attention in high school chemistry! I just learned that vinegar has a pH of around 2 which is much lower than I would have guessed. Maybe I should stop guessing............

I'm new to this game, so bear with me here. According to The Pool Calculator it would take 104 Litres of 31.45% HCl to drop the pH from 7.5 to 2.7. 16 Litres would drop pH to 5.2. Am I doing something wrong?

I had a choice between sand or cartridge. I went for the sand because I have vivid memories as a kid of having to clean black slime off the cartridge elements (maybe dad didn't use enough chlorine). Anyway, I now have a 600lb sand monster that isn't going anywhere, so I guess I'll have to get used to it! Thanks for the feedback.

My filter is a Tagelus sand filter. Does that use DE as well? I think the salt is what's killing the grass.

Thanks again!

I think I'll go with PC's suggestion. I don't intend modifying any of my sewer plumbing. I would simply remove the inspection cap, drop the hose into the pipe, backwash, remove hose and refit cap. No chance of backflow into house as the inspection pipe is well below the level of the house. Thanks for replies.

How much will 14kg of boric acid reduce my pH by?

OK, I'll go and get some borate and cyanuric acid today. Cheers.

I just had a new pool installed but I didn't have the filter backwash outlet connected to the sewer because the cost was prohibitive. It is legal where I live to discharge backwash water onto your lawn, but it's not good for the lawn. There is a sewer inspection point near my filter. It's a 4" pipe with a screw on cap. I would like to discharge my backwash water into this pipe by using my pool vacuum hose. The problem is, I haven't been able to find a way of adapting the 2" backwash outlet to take the vacuum hose. Even if I could, I suspect that the pressure of the water would just blow the hose out of the adaptor. Maybe there are other hoses I could use with bayonet or screw fittings? Has anyone come up with a solution to this problem?

It's early days yet so I don't know. My system uses a peristaltic pump to add a 1:5 dilution of muriatic acid as required to maintain the set pH. I'll replace the 15L acid drum with a smaller container so I can measure how much acid is being used. What would you consider to be a reasonable weekly acid consumption for a 50,000L pool? Thanks for the info so far. It's a steep learning curve and the pool shop people don't seem to undertsand the underlying chemistry.

Thanks, I think I have 8 position popups. Is there an easy way to tell? I have one 6-way water valve which cycles about every 1 minute. By my calcs each popup should complete a full revolution every 48 minutes. So in 3 hours each popup will do 3 3/4 revolutions. Does that sound right?