Offline Chlorinator (Pentair 300) inlet/outlet for small pool

[DancerX]

Hello All, I'm a long time lurker, I've learned quite a bit from this forum. I know the people here are down on tab chlorinators, but I'm thinking of installing one on my small pool (9000 gallons). Previously I've used puck floaters and occasionally get a stretch of many months where they work before I have to switch to liquid chlorine, or do a quick half drain and refill (takes 5 hours). The puck floaters need to be refilled every week, and I'm hoping with the chlorinator to be able to go on trips for 3/4 weeks without having a friend do anything to the pool. I've recently got an autofill and it's been great!

The pipe out of my cartridge filter elbows up immediately and has a 3 foot vertical section. On this there is a check valve. Then it elbows horizontal to a bypass/solar switch. Solar is not working so it's always on bypass. solar/bypass returns come together and elbow straight down to the returns.

I'm thinking of putting the chlorinator inlet right after the check valve and the outlet near where the returns go into the ground. I realize this does not give much pressure differential. The inlet will be a couple feet above the outlet, but there will only be a few feet of pipe in between the two. Will this work ok with an offline Pentair 300?

I know you're supposed to plumb the inlet before the filter for more pressure, but I've also heard this will clog your chlorinator.

I considered plumbing in the Pentair 320 inline, but that would require me to elbow the vertical return line to horizontal, then elbow it back to the returns. Seems too convoluted. I also note that this inlet and outlet in the 320 appear to be inches apart. There seems to be a pitot tube elbow for the inlet, just above that is the check valve for the outlet. The 320 does get gravity working on it's side to drop solution through the check valve, but I can't believe there is much pressure differential. Is there something I'm missing in my analysis? Is there some other magic that the 320 is doing? Why does the 300 need more pressure differential when the 320 appears to have almost nothing? The 320 appears to be the most recommended chlorinator on this forum. If the 320 works, I imagine the inlet/outlet locations I've selected will work.

I know there are people on here that are gripping that they only get 1-2ppm from chlorinators no matter what they do, but on my small pool that may be enough.

 

[Texas Splash]

Welcome to TFP! I would recommend posting some pics of your equipment pad from a couple angles so we can see everything well. That should help with replies.

 

[sande005]

I had a 300 (actually several) for decades. No issue with the inlet after the filter, and the outlet after the heater. It doesn't depend just on pressure differential, but also on the operation of the mini-check valve on the bottom of the unit, combined with the venturi effect of the water flowing past the outlet connection. Many will advise a check valve on the main pipe after the heater, and before the outlet attachment point. The hope is that any concentrated Cl water does not get sucked back into the heater when the pump is off, if there is any reverse flow. I never had one, and the heater is now getting to be over 20 yrs old, and is finally due for replacement. But a lot depends on your exact setup.
Get REAL familiar with the spare parts page on Amazon. Those bottom inlet check valves plug quickly. There's no cleaning, just throw and install a new. I always kept at least three new on hand. The BIG culprit is the tabs used. Most have a high amount of some kind of paste binder to keep them together as hard tablets. That paste plugs the check valve. No more affordable tabs for you!
The best were the Bioguard BASIC 3" tabs. They plugged it far less, but I still had to swap out the check valve 2-3 times a summer. It can be an exercise in futility to check other brands to see what kind of "other stuff" they use for binding. The cheapest could plug it in as little as a week.
How do you know it is plugged? The rate of tablet use goes way down - but more likely your pool turns green.

Leaving a pool running for 3-4 weeks, unattended, is a big risk. Too many other things can go wrong. Storm debris plugs the skimmers, filters get plugged and not cleaned, motors strain and burn out due to blockages, etc. I just sucked it up - heavy dose of liquid Cl just before leaving, a floater or two, turn it all off, and hope. But if I returned to a swamp, it was what it was, and spent the many hours over the next week or two getting it all back to normal. At least yours is smaller, and doing a drain/refill is less painful than de-swamping my 23,000 gal pool.

I've since upgraded to salt water, and glad I got rid of the chlorinator. But last year, still did the shutdown thing while gone on a 3+ week trip.

 

[Lake Placid]

If you decide to install a tab chlorinator, I would recommend only using an online feeder such as a Hayward CL200. Offline chlorinators are generally junk by design - there is a physical limit to how much water you can push through the flex tube that feeds them. I am doubtful you can go 3-4 weeks without loading any style tab feeder excepting some of the very large pentair commercial ones that are likely overkill for your pool.

 

[DancerX]

Thanks for the replies everyone! If you're curious this is what my flow diagram looks like :



Sounds like an offline Pentair 300 will work. I've marked the proposed inlet and outlet spots. As you can see routing for an inline 320 will be a little awkward and possibly reduce my flow. However, I now realize the 300 only has one inlet port. The 320 has two. This may be important because there are some small bubbles that perhaps indicate a small suction leak on my pool pump. Supposedly this may cause a chlorinator to accumulate air over time and stop to function. On the 320 you just have to move the inlet to the top port and it will work fine. So unless I can find a 300 that has another port, I may have to bite the bullet and figure out a way to plumb in the inline 320.

I very much like the idea of trying out a 300 though, because it will be much easier to install and remove if I decide to upgrade to LQ.

As for my dream of being able to go on a 3/4 week vacation without dealing with the pool, I do have people in the house that can watch the pool while I'm gone. They don't know much about pools (or are interested in learning ) but they can follow simple instructions - like "load the floater full of pucks and toss it in the pool until I get back". The last time I went on a long vacation with the house empty, I drained the whole pool first.