To understand problems with spa jets it is helpful to understand how jets function. Jets draw the air through the movement of the water combined with the use of a venturi. In most cases there is no need for an external blower to "feed" the air to the jets. Jets pull air on their own if they have a sufficient flow of water and access to air.
The diagram above shows the layout of a very basic venturi tee for mixing air and water. Pressurized water from the pump is fed in through the water inlet, air is drawn in through the air inlet, and a mix of air and water exits from the front of the jet.
The main functional part of the jet is the orifice in the center of the tee. All spa jets have an orifice in them. The size of the hole if the orifice determines now much flow the jets need to work correctly.
When the water passes from the larger pipe into the smaller orifice opening it must faster to get the all water through, we call this an increase in "velocity". The energy the jet gains in velocity if loses in pressure, this means that the water in the orifice is moving faster than the water in the larger pipes, but is at a lower pressure than the rest of the water around it.
When the water exits the tip of the orifice it is at a lower pressure than the air in the air supply pipe - the air in the air supply pipe is then sucked into the low pressure water stream and gets mixed in. This air/water mixture gives us the hydrotherapy jet action we all enjoy.
Where spa jets go wrong:
Modern spa jets are not quite as simple as the simple venturi tee we see above. In most cases the orifice is mounted in a removable “internal” assembly.
Above is a typical jet internal, this internal mounts inside a “jet body” in the spa wall. The water inlet is at the rear of the jet internal and the air intake is through the slot in the side of the internal assembly. The orifice is inside the internal where it is not visible in the picture.
Near the back end of the jet internal you will see a black seal ring on the side of the jet. When tightened into the jet body in the spa, this black seal ring will separate the high pressure of the water inlet from the air intake which is sucking in the air.
All jets have some sort of separator keeping the water pressure out of the air lines. When this separation no longer works correctly the pressurized water can leak into the air suction section. The pressurized water in the air intake can limit the amount of air in the jets making them feel less powerful. If the leak is large enough it can disrupt the flow or air to surrounding jets or even start leaking out of the air controls up above water level.
How do I fix it?
On most jets there are limited parts available so a replacement of the internal is the most common remedy. You can find jet internals and replacement parts in our replacement spa jet section.
If you do not see your jets in the jet section or cannot identify them, you can email a picture of them to our technical staff at: info@aqua-man.com. We can normally help identify your jets.
Many spa owners notice that their spa jets lose power over time. Often the suspect is a bad pump, but often a lack of power has to do with a spa jet problem.
