We have a new pool with the Paramount ClearO3 ozone system and an Intelliflo VS pump. Currently we have the Ozone system connected directly to the suction side of the pump at the bottom of the pump basket. We have comtemplated connecting the Ozone system below ground, but decided to keep it simple for now. The jury is still out regarding how well I think it is working.

Initially, we had a lot of issues with air getting in the return lines from the Ozone system. We verified this by disconnecting the Ozone system and replacing the pump drain plug. This completetly eliminated the problem.

To help solve the problem, Paramount recommended a few things. First, they have a new connector with a stronger backflow protecter to help stop air leaks in the connector. Secondly, they said that the threads on the Intelliflo are not all uniform and they recommend using a lot of teflon tape to help seal connector.

Also with the Intelliflo being a variable speed pump,its important how you set the level of Ozone output. To set correctly, you need to run the pump at the speed that will be its maximum each day. This is not the max speed of the pump, but how fast you plan to run it during the day. In my case, the Intelliflo is running at 2,300 RPM's when the cleaning system is running. I set the Ozone output in the ideal range while running at this speed. Later, when the cleaning system is off, the Intelliflo drops to 1,800 RPM's for normal filtration. In this state, the Ozone output indicator is lower than the ideal output.

We did all of these things and it has helped reduce the amount of air in the system. I'm still not sure if it is working right, because my PB doesn't seem to understand how they work so its hard to compare it to other pools.

Right now, I'm keeping my chlorine level at about 3PPM and the pool is staying clean. I've been told by Paramount that I should be able to keep Chlorine at 1PPM. I'm starting to drop the level of Chlorine a little to see how low I can go and still keep the pool clean.

YOU ASKED:
My question is whether I should replace the venturi and plumb the ozone in after the heater as it currently is, or should I inject the ozone at the suction side of the pump? I've looked at several ozone system manufacturers, including the one who manufactured my unit, and am seeing conflicting information. My preference would be to plumb into the suction side of the pump, but I'm worried about shortening the life of the Intelliflo. Any suggestions or feedback would be greatly appreciated.

Most pool/spa size ozone generators require negative pressure to draw air flow through the generator. The suction side of the pump is usually not low enough pressure, and the pump will be damaged both by cavitation and ozone.

Add the ozone a bit of distance before the filter, to allow some contact time. Make sure you have a method to allow the undissolved gas out of your piping, and direct this gas away from people.

Woodberg,
Thank you for your reply. The setup that you described is what I was contemplating. I'd be curious to hear how things go as you lower the chlorine.

Dlcz,
Thanks. I understand your argument about negative air pressure generation to draw the air from the ozone generator into the water stream, hence the use of the venturi in the pressure side installation.
However, could you explain the cavitation and ozone damage comment. Are you saying that independent of the lack of low pressure/vacuum issue, injecting any ozone directly into the intelliflo drain plug will lead to cavitation and ozone related corrosion in the pump?

YOU ASKED: However, could you explain the cavitation and ozone damage comment. Are you saying that independent of the lack of low pressure/vacuum issue, injecting any ozone directly into the intelliflo drain plug will lead to cavitation and ozone related corrosion in the pump?

Gas bubbles will take pits out of the impeller of a pump that is running with any significant impeller speed (>1800rpm) or running to high differential pressure. Self-priming pumps are somewhat tolerant, but not immune.

Ozone will drive any chlorine to corrode even passivated stainless steel, with especial vigor against areas with welding. Not sure if "Intelliflow" has any internal wetted metal parts.

To address Scott's concerns, ozone is not an economical choice as a secondary (in pool) sterilant. It does wonders for bromine-based systems, which is pretty much how Nature takes care of Her oceans. Having adequate dissolved oxygen (something a stagnant pool has little of), does wonders for algae control... and chlorine-controlled pools don't do natively.

Here is a link that might be useful: Chlorine poses threat to swimmer's health

Sorry to disagree with you but air bubbles and cavitation are not the same thing. Completely different physics going on. The damage caused by cavitation is not due to the air bubbles but is due to the rapid collapse of the air bubbles on the impeller vane in a very small volume. Read the link below on cavitation. Ozone bubbles will will not cause damage to the impeller.

Here is a link that might be useful: Cavitation

Perhaps there will be no damage, mas985. *I* have seen damage in high rpm pumps and/or high pressure boosts from entrained gas, whether it came in the suction side, or in the shaft seal. Pools do have the impeller speed, but the boost pressure is usually low. It depends on how small the bubbles are sheared into by the impeller...

You will agree that the pump will lose capacity while the bubbles are present right? This means that a 30 gpm pump is not displacing 30 gpm any more... which will reduce your filtration rate (in this case).

why you would inject any oxider upstream of all of your equipment?

Quote: "You will agree that the pump will lose capacity while the bubbles are present right? This means that a 30 gpm pump is not displacing 30 gpm any more... which will reduce your filtration rate (in this case)."

The Ozone injectors for residential pools do not produce that much gas to affect the flow rate through the pump or anything else for that matter.

The largest units produce only 1 gram per hour. The solubility of Ozone is 1 gram per liter so most if not all of the ozone gas will dissolve into water. Also, 1 gram of ozone is only a pint of gas per hour. Compare that to 1800 gallons of water that will pass in the same time at 30 GPM.

The amount of gas is so small compared to the amount of water, the pump will not even be affected by it.

gwgjr33, You should hook it up to the injector after the heater.

Any amount of ozone high enough to do your pool any good will be detrimental to the equipment if injected at the pump. ALWAYS sanitize AFTER equipment.

mas985 said: "The Ozone injectors for residential pools do not produce that much gas to affect the flow rate through the pump or anything else for that matter."

The injector is post-pump, requiring the horsepower of the pump to provide the suction. So of course it will not affect pump capacity if one uses an injector / eductor.

mas985 said: "The largest units produce only 1 gram per hour. The solubility of Ozone is 1 gram per liter so most if not all of the ozone gas will dissolve into water. Also, 1 gram of ozone is only a pint of gas per hour. Compare that to 1800 gallons of water that will pass in the same time at 30 GPM.

The amount of gas is so small compared to the amount of water, the pump will not even be affected by it."

The amount of ozone is the gas stream is nearly inconsequential to the amount of essentially insoluble nitrogen in the gas stream. It isn't the ozone bubbles, but the amount of dissolved gases in the water stream. From an underground aquifer, there is not much in the way of dissolved gases. From a pool, nitrogen is usually near saturation *before* additional air-with-some-ozone is applied. So regardless of how much ozone is made, how much total gas is applied is the issue. By injecting at pump suction, much less than rated ozone is made, because much less than rated gas flow is being moved in.

To those that are reiterating where ozone is to be applied, ozone applied just prior to filtration is how the large commerical pools do it, those that use ozone. Ozone quenches rapidly in sand or DE fitler, usually within less than a centimeter of depth. Not sure how it will fare in a cartridge filter such as the OP has...

dizc, Having a lot of formal training in chemistry (1 class in high school) doesn't enable me to argue with you. However, I have been installing ozonators on residential pools and spa since the mid 80's and every manual has always recommended downsteam injection. Maybe they didn't know what they were talking about?

Most of the commercial pools I have worked on do not have plastic injection molded pumps and filters either. What works for commercial is not usually applicable to residential. I have seen lots of ozone damage to plastic pool returns in residential pools though. As far as I know the 1/2 life of O3 is 18 minutes, plenty of time to do damage.

dlcz,

Sorry if I wasn't clear. I am NOT in favor of injecting Ozone into the suction side of the pump. I suggest following manufactures recommendations for installation of an Ozone generator as I do for any piece of equipment.

I was more interested in looking at this from a theoretical point of view if it was even possible. Based on Woodberg's post, it looks as though it is possible but it depends on some of the operating conditions.

Initially, what I took issue with is that injected air bubbles are the same as cavitation. As I pointed out before the physics are different. So the air itself is not damaging to the impeller and should pass without incidence much like it does when the pump primes or when there is a small leak in the suction side of the pump.

However, I would agree that with enough air flow will cause problems with pump efficiency and the pump could lose prime at the extreme. But this is all dependent on the amount of air introduced into the water flow. Again, Woodberg indicated this is dependent on the flow rate of the pump and the air injection rate of the unit which is logical.

In my previous post, I neglected the total air flow passed through the unit which was a very good point and can be quite significant. I was in a rush and didn't think about that so good catch.

From what I can tell, a typical ozone unit has a total air flow of about 15 SCFH which is a little less that 2 GPM but that is at the maximum setting. Neglecting any ozone that is dissolved, this could be a problem for low water flow rates but normally the maximum ozone setting would not be used with the minimum flow rate setting. This seems to be consistent with what Woodberg reported and means that you can adjust the settings to make it work (i.e. lower ozone production rate for lower water flow rates).

In any case, reduction in flow rates should be less than what is experienced with a dirty filter so that seems to be less of an issue. Air may accumulate in the filter but most filters have air bypass mechanisms to flush out air.

So let me reiterate that I am not suggesting that any one should do this only that it may be possible if absolutely necessary.
_________________

However, I would like to make a point about using ozone generators in general. First, I don't think they are necessary and really don't reduce the need for chlorine very much. The important part of any sanitation system is to have a residual in the water when you need it to kill bacteria. Chlorine is the most effective way to provide a residual and ozone simply cannot do this. Water must pass the ozone unit before the bacteria is killed. This could take several hours of pump run time before the bacteria is killed. Bacteria needs to be killed at the source within seconds, not hours which requires a minimum FC level.

At best, systems with Ozone might be able to operate at the same residual FC level as a SWCG (~5% of CYA level). The Ozone helps with oxidation which can help reduce the chlorine demand so you don't need to add as much each day but you still will need at lease the same residual as a SWCG.

Also, many of the reasons sited for Ozone use are bit deceiving and require further examination of the examples. Most of the problems sited about chlorine stem from the improper management of indoor pools. Often times these pools do not have any CYA in the water and have fairly high chlorine levels which can have very bad side effects. This is a dangerous condition but is easily rectified with proper pool water management.

Most indoor pools operate without CYA because there is no need for UV protection. However, without CYA, a very small chlorine residual of 0.1 ppm is required (based upon studies of kill rates at various chlorine levels). The problem is that it is very difficult to maintain the chlorine at this level so most indoor pools operate well above this level. This is what causes most of the problems with air quality and corrosion.

Contrary to popular belief, it is a good idea to have a little CYA in an indoor pool (~10 ppm) to help buffer the chlorine so it is not so reactive. Also, chlorine is easier to maintain since a CYA of 10 ppm requires about 1 ppm of free chlorine for proper kill rates. A 1 ppm FC with a 10 ppm CYA is much less reactive than a 0.1 ppm FC level at 0 ppm CYA. With the higher CYA, the bacteria kill rate is still very fast but the reaction with metal and fabrics as well as the evaporation rate is much less. So there are much fewer problems when CYA is used. However, too much CYA for given FC level can also cause problems.

Putting all the marketing hype aside, the safest pool is a properly maintained chlorine pool.

To removxpt:
I acknowledge your understanding. I suspect we are simply arguing over definitions. Upstream -> skimmer (etc,) -> pump -> (possible O3 -> )filter -> chlorinator (and / or other) -> return -> downstream. PVC, PE, even some forulations of FRP are extremely hardy to expsoure to low levels of ozone. Adding ozone downstream of the filter but upstream of a chlorinator, destroys some chlorine, and can degrade metal and some plastic parts downstream of the addition. The concept of allowing additional contact time for better use of ozone is thrifty, but if the pool is not constructed for that purpose, allows for unintended damage. There are residential pools that use ozone as the only disionfectant. They have *big* ozone generators, and do not use the usual bronze fittings and such.

To cascade:
If you add ozone prior to a sand filter or DE filter, there is no "half life". Ozone will complete whatever reactions it will drive *immediately*. No damage to pool returns or other downstream components from ozone. And no, cartridge filters are not the filters I mention above, and unless the filter is very dirty (or is carbon), there will be negligible ozone destruction across such a filter.

I am trying to be really clear here. We seem to be talking past each other...

Dizc, The injectors I am most familiar with require a low pressure release point (5psi or less)and rely on a differential pressure to operate. Even a compressor driven system would operate better under these conditions. The most common setup uses the high pressure point between the pump and filter (influent 20 psi +-) and a release point after the last piece of equipment (typically heater).

Even if the ozone "quenches" in the filter bed and loses its reactivity (is this the same thing?), It would be very difficult to inject between the pump and filter.

If you were able to inject ozone before the filter, it seems that a good portion of the ozone would rise to the top of the filter and be released into the rest of the equipment via the auto relief valve in the filter before quenching. This could damage the auto relief system and all downstream equipment.

To renovxpt:
I have designed and implemented systems that use eductors to deliver ozone gas into systems in excess of 80 psig. Not to plug brands, but Mazzei eductors do a fine job (I indirectly worked for them for a few years, and I own no stock).

One needs a place to allow the gas bubbles to separate from the flow stream. An Armstrong air release valve is a good choice for letting that happen:
http://www.armstronginternational.com/air-gas-vents-see-thru-ozone-1-avcw

If one allows one's car to plow through one's house, because one did not build brakes into it...
Add the horsepower to add ozone, add the mechanisms to allow the undissolved gas out, and blow the gas stream through a destruct. If one is going to save on chemical costs, it will take planning and capital to do that.

I am only telling the assembly here that the "big boys" do this, and the "big boys" do it the way I am saying it here. Maybe the problem is, that sales reps don't tell all that they should... when they represent a product line.

Dizc, Your "big boy" method hardly applies to the original posters needs. He has a downstream injector in place and is trying to treat a residential pool.

So the OP has an eductor, wonders if he wants to *not* replace it, and what I said about how eductors downstream of the pump is what the "big boys" do doesn't apply?

I do wish I had not managed to push your "hate" button. My apologies.

Okay

Ozone is probably less than 1% of the total gas sucked in from the ozonator. The rest is air. Hence the volumes of air sucked in through the high negative pressure of the suction side of the pump could be significant enough to cause cavitation. The downstream venturi in parallel with the variable flow constant pressure bypass valve provides just the right amount of negative pressure to provide the right concentration of the Ozone-Air mixture from the ozonator.