Converting Venturi Spa Jets to Active Blower Fed System

[alferz]

I have a 40-50 year old pool and spa combo where the spa spills over into the pool. The 3 "jets" are actually connected to the return line from the filter pump (no dedicated jet pump) and they are venturi type jets. I have a 1.5" PVC air line running to an upside down P-shaped air intake near the equipment pad, about 32' away and at the same elevation as the pool and spa water level. I validated with a shop vac this line is clear and open. The problem is, the jets don't draw any air through the air line because they are missing the nozzles and wall attachments that make the venturi effect work. I have searched high and low for these parts, contacted Inyo directly as well as several other spa jet parts suppliers. Most of them didn't respond to my inquiry and I'm thinking I will probably never find these parts due to the age of the pool.

I'm also replacing an ancient blower motor that feeds 11 3/16" floor bubbler holes via a second 1.5" air line. My thought was I would add a 3-way Jandy valve from a new blower, with one leg going to the floor and the other leg feeding the 3 venturi jets. Then I could adjust the air flow between the two points. Using the Jandy and Air Supply manuals, I calculated about 44" of back pressure and 40 SCFM between the jets and floor outlets. The low SCFM requirement would indicate a 1.0hp blower, but both of their spec sheets call for a 1.5HP blower for any back pressure over 40". That seems overkill given this small sized spa but I'm planning to go with 1.5hp anyway.

Just wondering if anyone has any experience doing this conversion. Is there anything I haven't accounted for in converting passive spa jets to an active (blower fed) system?

 

[mas985]

What makes a spa jet therapeutic and strong is the nozzle. Without it, the jets are not going to be very strong at all unless you can get the flow rate much much higher but that may not be possible with the given setup. Air really doesn't add much other than a pulsating effect and that may not happen as much without the nozzle. So adding a lot of air may not have much benefit.

Do you have any of the nozzles from the jets that you can post a picture of?

 

[alferz]

Hi Mark, yes I do, I actually created this diagram to help one of the supply houses track down the nozzles and wall attachments with dimensions. One of the nozzles pictured is in OK shape, but the other two were very brittle and I had to break them out to get them out of the wall so they are probably unusable now. One thing I did find was a 1.5" MNPT eyeball return fitting with either 3/4" or 1" eyeball nozzle so I was thinking I could use one of those to increase the pressure from the jets. I've seen the massage attachments too but haven't found one that would fit yet.

 

[mas985]

If you can match that thread with anything standard, it is pretty easy to build a jet. They are just pipe with a thread on one end and a small hole in the other.

You might even be able to use a die to thread a 3/4" PVC pipe (1.050" O.D.) if you can find the die. On the hole side, if you heat up the PVC and push it into a socket, you can form a hex shape for installing and removing. Epoxy the end and drill a hole the same size as the others.

The external fittings you can probably live without but I wouldn't be surprised if these fit:

Internal, Eyeball & Ring, Micro Jet - 10-3710 - INYOPools.com

10-3710 - Internal, Eyeball & Ring, Micro Jet

www.inyopools.com

 

[alferz]

Thank you, I had thought of something similar and tried a 3/4" threaded sprinkler riser, but those threads are a bit different. The nozzles are just slightly smaller and their thread is finer than the 3/4 MNPT riser's. Using a die is not a bad idea though to get the threads just right.

It seems that getting the venturi effect to work for air introduction would be nearly impossible without exact fitting parts no? In that case do you see any issue using one blower to feed both the jets and the floor?

 

[mas985]

If the venturi's are working properly, you shouldn't need a blower for those.

Also, feeding both from the same blower could be an issue since the bubblers on the bottom will need much more pressure than the venturi's so may not bubble.