Rainbow 320 Chlorinator problems

[shaneTX]

Hi
I need advice on keeping my pool balanced.

I have a rainbow 320 installed. I was testing this week and have noticed that it can’t keep my cl level at 3ppm. It seems to max out at 1ppm tcl. In the past , I was using 3 floating chlorintors to keep balance. I’m not sure how to diagnose what’s going on.

I have a 13000 gallon pool. I have a variable speed pump that runs almost constantly at 1200rpm which turns over all the water roughly every 4-5hrs. My cya is at 50.

I was thinking maybe this chlorinator is not sized correctly but I can’t really follow the sizing specs. I was also wondering if maybe it’s not working correctly. I was the considering using a scale to calculate dissolved cl over 24hrs. How else can I diagnose an issue?

I was considering converting to a swg but I’m worried that maybe my pool just consumes a lot of chlorine and maybe a swg can’t keep up either.

 

[tim5055]

I have never seen a pool that uses a 320 chlorinator only have 50 CYA, so I'm going to guess that due to continued use of 3" tabs your pool is overstabilized (too much CYA/Stabilizer) and you have reached the tipping point where things have started growing in the water. You are still able to keep the organic growth from exploding into a full blown swamp just by keeping the chlorinator maxed out.

Continued use of solid chlorine products in areas where there is not a normal regular replacement of water is a prescription for bad things to happen. In it's natural state, chlorine is a gas. Many large commercial pools actually use gas injection systems to chlorinate their pools. Now, to change chlorine into something we can use at home it needs to be bound to something to turn it into a solid. The "somethings" that are commonly used are stabilizer (also known as CYA), calcium, lithium, or --- get this water. All of these add a little salt to your water, but they add something else. Cal-Hypo add calcium, Tri-Chlor and Di-Chlor (tabs and most granules) add stabilizer, Lithium hypochlorite adds lithium and liquid chlorine adds - water.

While you do want some stabilizer, (the stabilizer helps shield the chlorine from UV degradation) but at higher levels it also impairs the ability of chlorine to do it's work. The higher the stabilizer level you have the higher the amount of chlorine you need.

How much Pool School have you read? Start with these:
ABCs of Water Chemistry
Recommended Pool Chemicals
How to Chlorinate Your Pool

The only way to know what is happening for sure is to conduct an Overnight Chlorine Loss Test. To do that you need your own accurate/quality test kit. Order a TF100 and at least include the XL option. That will give you what you need while you are clearing the pool, and probably enough reagents for a couple of years normal use.

The only other real option for a test kit is a Taylor K-2006. Be careful comparing prices because the K-2006 comes in sizes, designated by a letter. The basic K-2006 has .75oz bottles. You need to get the K-2006-C to get the larger bottles that you want. Even then it is a little short on the reagent & powder for the FAS/DPD test.

I also have the SpeedStir and Sample Sizer. They speed testing and accuracy.

 

[JohnT]

There is a screen in the bottom of those that gets clogged pretty easily. Take a look at that.

How confident of your CYA level are you? If you are using pucks, I'd bet your level closer to 150 than 50. Mine goes up 7.5ppm per week with the Rainbow 320

 

[Demegrad9]

Welcome to the forum!

What testing kit are you using to get those numbers? Here we only trust the K2006(C) or TF-100(XL). It's very unlikely that the continuous use of Trichlor pucks and that Rainbow 320 is going to be recommended as Trichlor constantly adds CYA and if your reading of 50ppm is correct (depending on your test kit) then you're already at the top of the range.

Since you're in Houston you pool probably gets plenty of sun and 3-4ppm chlorine loss per day is not out of the ordinary. You should do OCLT measurement to figure out if there's something in there consuming algae. That way we can tell if you're losing chlorine to the sun/bather load OR if it's a nascent algae or something like that.

In general it sounds like you have something growing in your pool that is consuming your free chlorine, so it's likely you need to start a SLAM. We can't know this until we have good test numbers.

 

[shaneTX]

Appreciate all the feedback. Good places to start.

My Pool is post hurricane Harvey and I just finished slamming my pool for 10 days to get a clean OCLT. I’m pretty confident nothing is growing because my fc and tc have stayed the same for 4days. I was trying to see what cl would drop to after slamming and was taking advantage of no swimmer load to reduce variables and try to figure out my pool chemistry and found this awesome forum of smart people.

Let me go double check cya level.

 

[SpringPool]

So you have one of the recommended test kits? If so great and I would say that after Harvey depending on where in Houston you are located your CYA was cut in half. I know all my numbers were about half. So that means pre Harvey it was probably 100 and if you stick with pucks you'll be right back up there.

What are your pool specs? Can you go to your profile and create a signatur? This way when questions are asked we know what your pool is.

Think about switching to liquid chlorine (bleach) or consider a salt water generator. That's the way I'm headed next Spring.

 

[setsailsoon]

Shane,

Is your problem you consume too many tablets or you don't have enough flow through the 320? The reason I ask is I have a similar sized pool and I use tablets when I'm out of town or to raise my CYA level. I maintain 50 CYA and use liquid chlorine per tfp most of the time. I'm guessing your problem has to do with the lower flow rate you experience at 1200 rpm. The 320 uses a pressure differential to route water through the cylinder which dissolves FC (and CYA of course). The 320 has been around for a long time and I'm guessing it's hydraulics are designed for a normal pump back when the flows were much higher. As a point of reference I use 2 tablets that provide about 5 ppm FC for 6-7 days with the dial setting half way open. I have a 2 speed pump that runs only on high speed for about 8 hrs per day though. I'm assuming you're wide open and this would mean your only way to increase the FC would be to add more tablets or use the accessory kit that allows you to tap higher pressure water further upstream of the chlorinator.

If you're happy dropping the water level periodically to maintain the CYA then I guess that's one way to do it. I find that for my size pool it's way easier just to use liquid bleach. Maybe something for you to think about?

I hope this helps.

Chris

 

[domct203]

shaneTX- Please confirm which test kit you are using.