Chlorine Tablets in the skimmer

[mdjjpapa]

I have read past posts, but couldn't find what I was looking for.

Does anyone know for sure if it is harmful or not to put chlorine pucks in the skimmer?

Some say the acid build up can hurt the pool equipment when the pump is turned on after being idle for a period of time, but just how much harm can be done for the few seconds the pH levels are very low? Doesn't the water in the pool equipment very quickly (seconds) return to the pool's pH level?

Thanks, David

[chem geek]

David,

Except for tablets specifically designed to go into the skimmer (e.g. BioGuard Smart Sticks), regular Trichlor tablets should not be put into the skimmer. The acidity is very high (pH is very low) and can harm the area around the skimmer, not just the pump when the water is turned on. I actually did that once and had my pool thermometer corrode so it doesn't take that long. Pool builders report not only that heaters and pump seals are damaged, but the plaster area around the skimmer gets pitted or weakened as well.

A single tablet of Trichlor in the skimmer may not be enough to cause serious damage, but repeated use could cause serious cumulative damage. Each blast of acid strips away a little metal or weakens pump seals each time, so that's at least once every day depending on how many pump cycles you have per day. It may also be that the acidity slowly diffuses up the pipe. An 8-ounce Trichlor puck that takes 5 days to dissolve in a floating feeder (that's my experience) would after 16 hours of pump off-time have 13% of it dissolve. The amount of water in a 1.5" diameter pipe that is 100 feet long is 1.2 cubic feet or only 9 gallons so that partial tablet would result in a pH of 4 if it dissolved in the volume of that pipe.

Even having tablets in a floating feeder can be a problem if it "parks" itself in one place. I partially rusted some stainless steel mounts in my pool that were closest to where my Trichlor feeder parked itself (this was before I looked into pool water chemistry and switched to using chlorinating liquid).

Of course, far worse would be pouring Muriatic Acid into the skimmer -- that's a longer exposure and far lower pH no matter how slowly you try and pour it (unless you use an eyedropper!).

Richard

[mdjjpapa]

Thanks Richard,

Everything thing you said makes sense. I have used liquid chlorine exclusively since the pool was built, but since I also have a salt system for producing chlorine (which or course can't keep up with demand), the tri-chlor pucks in combination with liquid chlorine seemed like an economic way to both lower pH (to compensate for the liquid chlorine's pH increase) and to add CYA required by the salt system (for some unknown reason I lose 40-50% of my CYA during the winter). Purchasing acid and CYA separately is becoming increasingly expensive.

I also have a leaf trap system that collects leaves in a basket in a cavity similar to the skimmer only much deeper; water flows from the pump and pool (using the "venturi" principle) through this cavity directly into the pool and has no metal parts, so I was thinking this would be an excellent alternative to the skimmer, but in your reply you mentioned the area around the skimmer can also be damaged, so maybe that won't work either. Plus you have a theory of the low acidity diffusing into the pipes, possibly back to the heater/pump.

If your theory about the diffusion is correct, then wouldn't in-line chlorinators using these pucks have similar issues? Especially since they are typically even close to the equipment?

Thanks, David

[chem geek]

If your theory about the diffusion is correct, then wouldn't in-line chlorinators using these pucks have similar issues? Especially since they are typically even close to the equipment?

Yup. So either my diffusion theory is wrong or such in-line chlorinators have one-way valves to prevent this or they in fact do have similar issues from diffusion, but possibly not from a "blast" of acidity since I think they are placed at the end after the filter and heater, similar to an SWG.

[spongebob55]

Unless the chlorine comes in contact with metal parts, which most systems don't have, I don't believe it's going to cause that much of a problem. Right?

[waterbear]

Yup. So either my diffusion theory is wrong or such in-line chlorinators have one-way valves to prevent this or they in fact do have similar issues from diffusion, but possibly not from a "blast" of acidity since I think they are placed at the end after the filter and heater, similar to an SWG.

Inline chorinators are plumbed AFTER the pump and heater so the chlorinated water is returned to the pool and does not go through the equipment. They also do not 'dispense' the chlorine unless the pump is running and many have check valves before gthem to prevent the heavily chlorinated and acidic water from backing up into the heater. The actual chlorinators themselves are made of materials that are desgined to stand up to the low pH and high chlorine levels (such as speical o-ring materials, etc.) but they still do show degredaton after a period of time.