Spa Jets Explained

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SPA Jets Explained

Consider a simple spa jet. Spa Jets have 3 main connections – water in, air in, and a water and air mixture outlet. The water is pushed into the jet by pressure from the pump and flows through and comes out the front. This is how the air gets mixed into the pressurized water stream that we will be discussing.

How Spa Jets Work

The air gets mixed into the pressurized water by use of a venturi inside the jet. The venturi effect happens at the tip of the orifice which is a small hole inside the jet that all the incoming water gets pushed through.

To understand the venturi effect you have to first understand the way fluid acts inside a pipe. If we reduce the size of a pipe with fluid moving through it, the velocity (speed) of the water increases, but the pressure in the pipe decreases. So if we have spa water flowing through a 2” pipe and we reduce the size to 1.5” for part of the run, the water in the 1.5” section moves faster but at a lower pressure.

If you look inside a spa jet they all have a reduction in the internal plumbing size, we call this reduced size section the “orifice”. The most common size of the hole in the orifice is 5/16” of an inch. This means that we reduce the incoming water feed that was lets say 1” pipe, and we force all this water through a hole just over a 1/4” wide.

This causes a section of the water to travel at a higher velocity and at a much lower pressure. This low pressure at the tip of the jet orifice is lower than the pressure of the air in the atmosphere outside. Since the outside air is a higher pressure than the water at the tip of the orifice, air gets pushed into the water stream at the tip of the orifice and mixed into the water. This water and air mixture then flows out of the front giving us the jet action we are all familiar.

What goes wrong with Spa jets?

Most complaints about spa jets have to do with them no longer mixing air properly. Customers will report that the jets are “broken” or not working, they will also sometimes refer to the pump “not being as strong as it used to be”, or even talk about the air controls or the air blower being broken.
Jet malfunctions usually lead to weak jets or jets with no air in them at all, but they can also lead to water shooting out of the air controls or a the jet sucking water in instead of blowing water out.
Almost all jet problems are centered around the orifice. I will list some of these troubles below:


Insufficient water input – if the pump is not delivering enough water to the jets they may not develop a low enough pressure inside to suck air from the outside world effectively. This can cause jets to be weak or have no air at all. The diameter of the hole in the orifice determines how much water a jet needs to work properly. If you have insufficient water input it can mean that you have a dirty filter cartridge, an obstruction in the pump impeller, or even an undersized pump for the amount of jets you have.

Too much water input – if the pump is over sized it can cause back pressure inside the jet after the orifice, this can cause the jet to not draw air correctly by applying pressure inside the jet where the low pressure is supposed to be formed. This back pressure is between the orifice and the eyeball at the front of the jet where the water and air mixture come out. Sometimes this problem can be relieved by increasing the size of the eyeball in the front. I have seen this problem most often in gunite spas.
Another problem with the older style gunite spa jets is the length can be an issue. With the orifice tees set back inside the wall the length of the pipe between the orifice and the front eyeball can vary greatly. The length of the pipe run itself can cause back pressure with long piping runs through walls it is often necessary up size the eyeballs, or even reduce the size of the orifice opening in the back of the jet and reduce the water flow. Modern design gunite jets move the orifice to the front and eliminate this issue.

Gasket/O-ring Problems – many modern jets have the orifice inside a removable jet internal. On these jets there is often a gasket or o-ring that separates the water pressure area from the low pressure air suction area. When this separation breaks down the high water pressure can leak over to the low pressure air side making the jet not draw air correctly or at all. If this leakage gets severe enough it can also cause water to come out of the air controls.

Plugged Orifice – a small obstruction can get lodged it the orifice obstructing the water flow. Running a screwdriver or other long, thin object through the orifice will often knock it loose, this works best with the jet pump running to help push the object out. If the the object is too large, you will sometimes need to remove the orifice and manually pull the object out of the jet.
Note that other jets may be affected from a single obstruction. The air line on the plugged jet is usually hooked to the air lines from other spa jets. The neighboring jets will still be drawing a suction on those air lines. Sometimes this will cause the surrounding jets to suck water through the air line backwards through the plugged jet, causing the plugged jet to be pulling water into the eyeball instead of outward. This usually only happens on inground spas where the air intake is far away, or for any reason, easier for one jet to pull water from another jet than to pull air from the air intake.

This Article is courtesy of Spa Parts Plus

Until Next Time....

Well the holidays are over now what?

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Well the holidays are over now what?


It back to reality and the tasks at hand, paying off the credit cards and getting back to some normal life and responsibilities. 


Now for those of you that have a spa and love using it over the winter now is a great time to get back to monitoring the water chemistry and since there most likely were a lot of users over the holidays it probably needs close attention right now.


This will be the time you need to give that filter or filters a good filter soak as to get rid of all the body oils and things that have built up over the last month or so.


Just hosing the filter off will not do it, you need to get a filter cleaning solution such as Filter Perfect made by natural chemistry. Take the filter out and place in a bucket of water, be sure that the water covers the filter. Remove the filter from the water and add the filter cleaning solution and mix, then place the filter back in the bucket and soak over night.


The next day remove from the solution and lightly hose off the grids. Re-install the filters into the spa and you should be back in business for another couple of months. Those of you who have a back up filter are in great shape as you can take your time and just swap out the dirty filter for a clean one and then soak that one at your leisure.


Be sure to test the water to see where everything is at now, usually the PH will be low after a heavy bather load so be prepared to add PH and or Alkalinity to get the water back in shape, REMEMBER to add the products one at a time at a rate of no more than 2 tablespoons per 500 gallons of water and allow water to circulate for 20 minutes then retest and add more as necessary.


Always adjust the Alkalinity first then the PH and then the Calcium Hardness, get those levels good BEFORE you start the chlorine or Bromine treatment.  If these chemicals are off the sanitizer will not work effectively and you will find it a pain to get the water back in balance.


If you take your time and do it one step at a time you will have the water back in shape in no time at all and can get back to enjoying the spa for yourself again.


Until Next Time...

Why Is My Pool/Spa Filter Blue?

It's been a while since my last post, I have been very busy opening pools and spas and getting everybody's water balanced. I have come across some new issues as of late that I would like to share with you.

I had 2 separate customers call me and say that  the pressure in their filters went way up and even after they back-washed the pressure still was high. So after a few phone calls and a service call I have come to the conclusion that this is a metal's issue.


In both cases when I opened up the filter the elements were a blue color, I find this to be a by-product of Magnesium that has been oxidized. When copper is oxidized it turns a greenish color,  Iron will turn reddish, and Magnesium can turn Blueish, or a Grey tone.


 My solution to this problem is a metal remover such as Conquest etc, these product's will shield the metals in the water from the Chlorine so it will stay in suspension and not discolor the water of filter. These product's also helps in the removal of set in staining on vinyl liners and plaster pools. If you can't find Conquest, Natural Chemistry has a Metal Free product that works real well.

 So if you are experiencing discolored water or a funky colored filter take a water sample to your local pool store and have the metal content checked and pick up some metal remover and bring the sparkle back to your pool or spa.

Until Next Time...