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Thread: Question about spa jets with a blower

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    Question about spa jets with a blower

    Hi TFP

    I have a problem with my spa jets - and am doing everything I can to try and research the problem before posting a generic 'help' request. I am sure my problem is already answered in one of the threads here, I just need to piece together a few more details.

    These are the two threads I have been focusing on

    no-more-bubbles-out-of-the-spa-jets-t39227.html
    pump-not-getting-enough-water-flow-for-venture-effect-t61132.html

    The background - I have an in-ground pool with a spa that overflows into it. (It was built in 2000, and we bought the house in 2010). Since we have been here we have always had to run the air blower for a few minutes when switching to spa mode to encourage the jets to start acting like a spa (the venturi effect?). We could then turn off the blower and the jets would work ok - although certainly some seemed to be at a lower pressure than others. I never thought this was behaving correctly - but it got the job done.

    In the past few weeks this process has stopped working - as soon as we turn the blower off the jets go back to just shooting water into the spa with no noticeable air in the stream (a few bubbles here and there). I have also noticed that one of the water returns into the pool itself has a few bubbles in it.

    One of the main questions I have is that, given there is an air blower, should there also be a separate air vent for when the air blower is off? Or is the air pulled down the same tube that the blower is attached to? I can't find anything that looks like it it would otherwise be an air intake for the jets?

    Appreciate any help in understanding how this is meant to work!
    25k gal, IG plaster, 2HP centurion pump, Purex Triton DE, overflow spa, zodiac blower

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    mas985's Avatar
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    Re: Question about spa jets with a blower

    Welcome to the forum!

    First things first. Please read through this and follow the instructions: pool-school/read_before_you_post

    It is difficult to answer questions without details.

    One of the main questions I have is that, given there is an air blower, should there also be a separate air vent for when the air blower is off? Or is the air pulled down the same tube that the blower is attached to? I can't find anything that looks like it it would otherwise be an air intake for the jets?
    Generally, if a spa jet requires a blower to be installed so that the jets start to work, it should be used all the time and not just at start. The blower supplies the air to push out the water in the air pipe and yes there is only one air pipe and the blower is attached to it. If shut off, the blower acts as restriction and so air does not flow as freely. You may not need the blower at all but to find out, you need to remove it completely from the air pipe.

    Second, I am not sure how your spa jets are plumbed but if the same pump is used for both the jets and the filtering, the filter may be getting dirty which would reduce the action of the jets. But again, this might be overcome by having the blower run all the time.
    Mark
    Hydraulics 101; Pump Ed 101; Pump/Pool Spreadsheets; Pump Run Time Study; DIY Acid Dosing; DIY Cover Roller
    18'x36' 20k plaster, MaxFlo SP2303VSP, Aqualogic PS8 SWCG, 420 sq-ft Cartridge, Solar, 6 jet spa, 1 HP jet pump, 400k BTU NG Heater

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    Re: Question about spa jets with a blower

    Mark - thanks for your reply, and the link to the posting instructions

    Some more info:

    * The pool is approximately 25k gallons. The spa is attached and 'waterfalls' into the pool when in pool mode
    * It uses a DE filter (although we are using ZeoFiber) - a Purex Triton
    * Both pool and spa water flow through the filter, even when in pool mode (I have tried everything in recirculate mode just to see if the filter is having any effect either way)
    * The air blower is a Zodiac Polaris 2HP
    * The pump is a 2HP centurion model - one speed
    * Flow control is via two Jandy actuators
    * We also have a pool cleaner with a dedicated pump

    A picture can (sometimes) tell a thousand words - here is the pad:

    [attachment=0:dlaqebc6]PPuDrMN_small.jpg[/attachment:dlaqebc6]

    Larger version on imgur

    Today I drained the spa below the jets to get a better idea of what is going on. Having seen them in action above the waterline I am not convinced there is any (intended) venturi effect going on - and what we see in spa mode (with blower off) is just a pretty strong water flow.

    I did notice that one of the jets is much less powerful than the other. And if I block it in spa mode the whole thing kind of shuts down like it creates some kind of airlock somewhere...all of the spa returns stop pumping water. At this point activating the blower won't get them back...I have to put it in spa fill to push enough water through them to unblock it.

    So it seems to me the problem is now that somewhere there is air being pulled into the waterside plumbing somewhere? As I mentioned before I do see air bubbles in one (of the six) pool return outlets?

    Confused!
    Attached Images Attached Images
    25k gal, IG plaster, 2HP centurion pump, Purex Triton DE, overflow spa, zodiac blower

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    mas985's Avatar
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    Re: Question about spa jets with a blower

    Have you backwashed the filter recently? If not, try that first.

    Do the jets run ok with the blower on all the time (i.e. from the start and never shut off)?


    Also, per the instructions, please put all your equipment in your signature (see mine) and also set your location in your profile. Both can be done through the control panel.

    ucp.php?i=profile&mode=signature
    Mark
    Hydraulics 101; Pump Ed 101; Pump/Pool Spreadsheets; Pump Run Time Study; DIY Acid Dosing; DIY Cover Roller
    18'x36' 20k plaster, MaxFlo SP2303VSP, Aqualogic PS8 SWCG, 420 sq-ft Cartridge, Solar, 6 jet spa, 1 HP jet pump, 400k BTU NG Heater

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    Re: Question about spa jets with a blower

    Thanks Mark

    The filter gets backwashed fairly regularly - last time was about two weeks ago. It is running at about 18-20 psi now.

    The need to run the blower initially to get the spa jets to flow has always been a problem (for us, at least - we have been here 3 years).

    With the blower on, the jets appear to run fine all the time. In general we don't like to use it with the blower on as it is pretty noisy (only about 20ft from the pad)
    25k gal, IG plaster, 2HP centurion pump, Purex Triton DE, overflow spa, zodiac blower

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    mas985's Avatar
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    Re: Question about spa jets with a blower

    As I pointed out earlier, most spas with a blower require the blower to run all the time. The blower acts as a blockage when shut off so the venturis will not get enough air. It is very rare that you can run the jets without the blower and not designed to do so. If you had been able to do this and you can't now, 9 times out of 10, it is because of a dirty filter. I would still try to backwash just to eliminate the possibility.

    The only other explanation is that there is some other blockage in the plumbing. So empty the pump basket, check the pump impeller and check all the valve settings. Last resort, you can remove all of the jet nozzles and flush the lines to make sure there is nothing stuck in the plumbing.
    Mark
    Hydraulics 101; Pump Ed 101; Pump/Pool Spreadsheets; Pump Run Time Study; DIY Acid Dosing; DIY Cover Roller
    18'x36' 20k plaster, MaxFlo SP2303VSP, Aqualogic PS8 SWCG, 420 sq-ft Cartridge, Solar, 6 jet spa, 1 HP jet pump, 400k BTU NG Heater

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    Re: Question about spa jets with a blower

    Mark

    Thanks - it is pretty clear to me that there is no expected Venturi effect with these jets. That said, the way they behave with just water being ejected is actually quite nice.

    Once they are working ok, the jets are very powerful. The basket and impeller are clear. What is interesting to me is that one of the jets is much weaker than the others...and blocking it causes the whole system to stop?

    Naiively, to me, this says something is allowing air to get in the water side somewhere?


    25k gal, IG plaster, 2HP centurion pump, Purex Triton DE, overflow spa, zodiac blower

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    mas985's Avatar
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    Re: Question about spa jets with a blower

    Quote Originally Posted by Noelep
    Once they are working ok, the jets are very powerful. The basket and impeller are clear. What is interesting to me is that one of the jets is much weaker than the others...and blocking it causes the whole system to stop?

    Naiively, to me, this says something is allowing air to get in the water side somewhere?
    A venturi jet is made up of a venturi Tee with a nozzle insert that looks something like this:



    There are two connections to the tee, the lower is a water pipe the upper an air pipe. When water travels out of the nozzle the venturi creates a low pressure area around the nozzle which then draws air into the tee from the air port. The air and water mix to cause bubbles out of the jet. When you block the wall fitting, you disrupt the water flow and it is forced back out the air pipe. This can have an effect on the other ports as well since they are all tied together. If you were able to just block the nozzle itself, this would not happen. But the nozzle is deep within the spa wall.

    Also, I understand that you are not seeing a venturi effect but that can be due to either lower than normal water flow or lower than normal air flow. So if there is a blockage in either one, it can disrupt the venturi and you won't see any bubbles.

    Have you tried cleaning the filter and flushing the jet lines as I suggested earlier?
    Mark
    Hydraulics 101; Pump Ed 101; Pump/Pool Spreadsheets; Pump Run Time Study; DIY Acid Dosing; DIY Cover Roller
    18'x36' 20k plaster, MaxFlo SP2303VSP, Aqualogic PS8 SWCG, 420 sq-ft Cartridge, Solar, 6 jet spa, 1 HP jet pump, 400k BTU NG Heater

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    Re: Question about spa jets with a blower

    Mark,

    Thanks for the feedback. The filter is clean - but doesn't appear to have made any difference. I will be able to get to clear the jet lines on the weekend. Is there a recommended way to do it?

    I am also interested to understand where the tee would (should?!) be pulling air from if the blower is off. As you said above - if the blower is off then it would actually be creating a vacuum effect?

    Is it possible that my arrangement is not meant to have any passive venturi effect?

    thanks!
    25k gal, IG plaster, 2HP centurion pump, Purex Triton DE, overflow spa, zodiac blower

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    mas985's Avatar
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    Re: Question about spa jets with a blower

    Quote Originally Posted by Noelep
    I am also interested to understand where the tee would (should?!) be pulling air from if the blower is off. As you said above - if the blower is off then it would actually be creating a vacuum effect?

    Is it possible that my arrangement is not meant to have any passive venturi effect?
    I think I covered this before before but lets try again.

    1. Since you have a blower, the spa is not designed to run the venturi's passively. It may work on occasion but it really isn't setup to do that. There is only one air line and if you have a blower, it blocks the air line when shut off. It is this single air line which feeds the air port on the veturi tee. So you really can't expect it work properly when the blower is off.

    2. However, if you completely remove the blower from the air line, then there might be a chance the jets work properly passively. But you need to completely remove the blower from the air line to test this. Most blowers will just pull of the air line so it isn't hard to try. If it works great, if not, you need the blower and you need to run it all the time.

    3. Any spa can be designed for a passive air pipe but many PBs do not know how to do this so they simply opt for the blower since it is easy and will almost always work.
    Mark
    Hydraulics 101; Pump Ed 101; Pump/Pool Spreadsheets; Pump Run Time Study; DIY Acid Dosing; DIY Cover Roller
    18'x36' 20k plaster, MaxFlo SP2303VSP, Aqualogic PS8 SWCG, 420 sq-ft Cartridge, Solar, 6 jet spa, 1 HP jet pump, 400k BTU NG Heater

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