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Putting on the pressure: losing vacuum pressure is one of the leading causes of ozonator malfunction.

If you've ever had trouble installing ozone on the return line of a spa or swimming pool, you are not alone. Occasionally, we get calls from people who cannot get enough vacuum or have lost vacuum in their ozone venturi injector. There are several reasons for such problems.

Here are several examples of what causes vacuum pressure loss and how to remedy it:

Improperly adjusted injector valve

A venturi develops suction through a pressure drop. The greater the pressure drop, the greater the suction.

One of the most common mistakes is not adjusting the injector bypass valve properly. Closing the injector valve results in a greater pressure drop across the injector; thus, a greater amount of suction is created. Opening the valve has the opposite result: a lower pressure drop and lower suction.

Venturi sized incorrectly

When installing an injector in a pool or spa application, you must make sure that the venturi is sized properly for the flow (gpm) of water and the pressure (psi) of your pump.

An oversized injector will result in low vacuum and could even cause water to shoot from the suction port. Under-sizing an injector will result in insufficient water flow and inadequate vacuum.

Contact your injector manufacturer for the proper operating range. Once you have that information, you should then match the gpm and pressure rating from the pump to the injector.

Back pressure on return line

One cause of venturi vacuum failure is water backing up into the ozone generator. I have found that water backs into an ozone generator when kids (or even adults) stick fingers or toes into a jet that is returning water (and ozone) back to the spa. Obstructing the jet causes back pressure on the water return line. If the remaining jets cannot compensate for the increased back pressure, vacuum will be lost and, in severe cases, water will back up into the ozone generator. To solve this, install a high-quality check valve or a water-release valve.

To reduce back-pressure problems with pools, change eyeball fittings on the return line to a smaller size. If the fittings are less than 1 inch, increase them to at least a full 1-inch return fitting.

You can also reduce return-line back pressure by reducing the quantity of fittings and/or using 45-degree PVC fittings instead of 90-degree PVC fittings after the injector.

Dirty filter

Adding an injector to the filtration system increases the pressure requirements of the pump. As the filter grows increasingly dirty, vacuum flow developed by injectors decreases.

A clean filter is vitally important for proper operation of your injector.

Two systems on same line

Installing an ozone injector system into the same return line as an in-floor cleaning system (ICS) could cause poor vacuum.

If you're using a standard-sized pool injector with an ICS, you won't get the proper vacuum because the system creates a sizable amount of back pressure when in normal operation.

The solution: Increase the size of the venturi injector. This provides more water flow for sufficient vacuum while also allowing for sufficient back pressure for the in-floor cleaning system.

Installing an Ozonator

This diagram of an ozonator installation on the return line of a pool shows the location of the injector valve--a common source of trouble if service technicians don't take the time to adjust it properly.


Babcock is the national OEM sales manager at DEL Ozone in San Luis Obispo, Calif. He is a 17 year company veteran and an active NSPI member.
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Title Annotation:Technically Speaking
Author:Babcock, Wayne
Publication:Pool & Spa News
Date:Sep 5, 2003
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