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Thread: Hot Tub losing prime after 30-40 minutes?

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    Hot Tub losing prime after 30-40 minutes?

    Hi,
    I have a acrylic spillover spa that shares the pool pump & filter. After about 30-40 minutes of use the hot tub starts to lose prime. At the same time the hot tub is losing prime I can hear gergaling noises coming from the pcv "U" "J" vent traps installed above ground behind the spa/pool. It sounds like air is being sucked in throw those PCV pipes? This also seems to happen when the heater is on....
    Any ideas what the problem could be and how to fix it???
    Thx

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    Re: Hot Tub losing prime after 30-40 minutes?

    Welcome to TFP!!

    Sounds like a return to the pool may be slightly open and you are directing some of the spa water back into the pool.

    Happy New Year! We'll be here to help!
    Luv& Luk
    -Ted

    Having done construction and service for 4 pool companies in 4 states starting in 1988, what I know about pools could fill a couple of books - what I don't know could fill a couple of libraries :-D

    POOL SCHOOL, TF Testkits, Jason's Pool Calculator, CYA vs. cl chart, (Just a few DARNED handy links!)

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    launboy's Avatar
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    Re: Hot Tub losing prime after 30-40 minutes?

    The gurgling is probably just the air ilnets for venturi jets. This is on the return side and shouldn't be the cause of your problem. Have you checked to make sure your pump stainer lid is not what's letting the air in? Does the water level in the spa stay the same?

    HTH,
    Adam
    18' x 42" Intex Easyset Pool, with 16' x 52" deep end in the middle. Approx. 5500 Gal.
    Hayward Power-Flo LX 1 HP, 100# Jacuzzi Brand Sand Filter(Piped underground so it looks nice) 8)
    3 - 2' x 20' Solar Pool Heater Panels(roof mounted)
    Goin' on 9 summers...NOBODY thought it would last this long.
    Buried Portable Spa sharing pumps and water with pool (Almost complete project)

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    Re: Hot Tub losing prime after 30-40 minutes?

    This is a great forum. Thanks for the info.
    The water level stays the same. After 30-40 minutes the pump just starts to lose prime and suck air. I will check the pump lid, but it does not cause a problem when running the pool. I have checked the heater and I can not find any leaks? We do not use the blower for the air bubbler.
    I think the gurgling is to much of a coincidence to not be associated with the problem? It may not be the cause, but it is at least symptom of the cause? The only time it ever gurgles is when the pump is losing prime, running the hot tub. What is the function of this above ground U/J vent? Is it connected to suction side?
    Thanks

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    launboy's Avatar
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    Re: Hot Tub losing prime after 30-40 minutes?

    Usually the vent is for an air intake for the jets. If you don't use an air blower and still have bubbles coming out then you have venturi jets. This Should be sucking air all the time when the jets are producing bubbles. When the pump has full prime the water entering the venturi woudn't have air in it so it may be quieter, but when the pump starts pushing bubbles through with it, this may cause the sound you're hearing. An easy way to check if this is in fact an air inltet(s) would be to seal it with a rubber plug or maybe even duct tape.

    The pump lid could still be the culprit even though it's not an issue with pool use. There may be better flow through the pool suctions causing it not to suck air. Then when you switch it to spa mode there is more suction and more negative pressure on the lid causing it to leak air. How many suctions are in the pool and what size pipe are they, how many are in the spa and what size pipe?

    One other cause, though unlikely, is that some air is being sucked in through one of your suctions, most likely the skimmer in the spa if the water level is too low. If you have jets near your feet that blow bubbles, some of these bubbles may be getting sucked in and causing your symptoms.

    The last option, is that you just have a plumbing leak on the suction side piping. This will be the most expensive to fix, but second most likely to be causing the issue. There's a good article in Pool School about leak detection. Might be worth having a look.

    HTH,
    Adam
    18' x 42" Intex Easyset Pool, with 16' x 52" deep end in the middle. Approx. 5500 Gal.
    Hayward Power-Flo LX 1 HP, 100# Jacuzzi Brand Sand Filter(Piped underground so it looks nice) 8)
    3 - 2' x 20' Solar Pool Heater Panels(roof mounted)
    Goin' on 9 summers...NOBODY thought it would last this long.
    Buried Portable Spa sharing pumps and water with pool (Almost complete project)

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    Re: Hot Tub losing prime after 30-40 minutes?

    What puzzles me about this issue is that it takes 30-40 minutes before it starts. A suction side leak would be immediate. Water level too low would be as well. It has to be something that changes after that period of time but I have no clue what it is.

    I have no spa experience so others with spas might be able to think this thru and offer a possibility of what might change after that time period for the condition to start.
    Dave S.
    42k vinyl and concrete pool, 1.5hp pump, 140gpm filter
    TFTestkits , PoolMath , Pool School

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    Re: Hot Tub losing prime after 30-40 minutes?

    The time delay is strange. I think it has some thing to do with after the hot tub heats the heater goes idle for a while (as it should) and then re-fires to heat the tub back to the set temp(98). It seems to happen at the point the hot tub is reheating? Maybe the heat is expanding something allowing air in???

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    Re: Hot Tub losing prime after 30-40 minutes?

    Quote Originally Posted by launboy
    Usually the vent is for an air intake for the jets. If you don't use an air blower and still have bubbles coming out then you have venturi jets. This Should be sucking air all the time when the jets are producing bubbles. When the pump has full prime the water entering the venturi woudn't have air in it so it may be quieter, but when the pump starts pushing bubbles through with it, this may cause the sound you're hearing. An easy way to check if this is in fact an air inltet(s) would be to seal it with a rubber plug or maybe even duct tape.
    It has a blower motor but we do not use it. So we have no air coming through the jets.
    The pump lid could still be the culprit even though it's not an issue with pool use. There may be better flow through the pool suctions causing it not to suck air. Then when you switch it to spa mode there is more suction and more negative pressure on the lid causing it to leak air. How many suctions are in the pool and what size pipe are they, how many are in the spa and what size pipe?[quote:27d310nl]Flow is better with the pool. It has 2 large 8 inch inlets + skimmer. The spa has 2 4 inch inlets and no skimmer. The pump is 2 1/2 hp
    One other cause, though unlikely, is that some air is being sucked in through one of your suctions, most likely the skimmer in the spa if the water level is too low. If you have jets near your feet that blow bubbles, some of these bubbles may be getting sucked in and causing your symptoms.
    No spa skimmer and the water level is normal and well above the inlets. No bubbles in the water.
    The last option, is that you just have a plumbing leak on the suction side piping. This will be the most expensive to fix, but second most likely to be causing the issue. There's a good article in Pool School about leak detection. Might be worth having a look.
    Thanks I will check it out now!
    HTH,
    Adam[/quote:27d310nl]

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    Re: Hot Tub losing prime after 30-40 minutes?

    While I don't really want to put this thought into the cosmos -- Many builders are confused by the pre-plumbing configuration with Triac and Baker (Spillway) spillover spas. Unless the heater operation is tied to valve movement, I'd not suspect the heater. Does your prime loss occur ONLY when in "spa mode"...that is, with the spillover feature shut off? Are your pool-spa-spillover operations controlled with a Jandy/Goldline/Pentair/etc. system, or do you have to manually go move valves to change to mode? Are the valves "ball valves" or "Jandy Valves"?

    I've had lots of recent experience with builders making the wrong connections to the spillover spa. The Baker, for example, when ordered "pre-plumbed" assumes that the venturi intakes will be the ones ON THE SHELL, and if your builder has created venturi openings in another location, the venturi plumbing at the spa must be capped off. This is especially suspect if your builder has added a blower to the plumbing configuration. Do you ever get water squirting out of the venturi's, especially with the blower on?

    This very slow loss of prime ONLY in "spa mode" suggests that the problem lies in the water flow in that mode only, and might be related to the plumbing. One of my best builders (now) went through an initial phase of most all of his elevated, spillover spa configurations lost water from the spa...it was a plumbing error, easily solved.

    One final question...when in "spa mode" with the pump OFF, is there any water loss in the spa overnight?
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    Re: Hot Tub losing prime after 30-40 minutes?

    Quote Originally Posted by budster
    While I don't really want to put this thought into the cosmos -- Many builders are confused by the pre-plumbing configuration with Triac and Baker (Spillway) spillover spas. Unless the heater operation is tied to valve movement, I'd not suspect the heater. Does your prime loss occur ONLY when in "spa mode"...that is, with the spillover feature shut off? Are your pool-spa-spillover operations controlled with a Jandy/Goldline/Pentair/etc. system, or do you have to manually go move valves to change to mode? Are the valves "ball valves" or "Jandy Valves"?
    I would completly agree that the builder was confused by the Baker Spa. That became apparent when they installed the spillover flush with the pool wall! The heater operation is somewhat tied to valve movemnt. When I press spa on the Intelitiouch panel the heater kicks on and the Pentair CVA24 valves move. Yes it only loses prime in SPA mode. The manual valves are Pentair branded aswell.
    I've had lots of recent experience with builders making the wrong connections to the spillover spa. The Baker, for example, when ordered "pre-plumbed" assumes that the venturi intakes will be the ones ON THE SHELL, and if your builder has created venturi openings in another location, the venturi plumbing at the spa must be capped off. This is especially suspect if your builder has added a blower to the plumbing configuration. Do you ever get water squirting out of the venturi's, especially with the blower on? [quote:2znds55s]The Baker Spa was ordered pre-plumed. Are the 2 knobs on the back of the spa venturi openings? They do not really have much affect when turned either way?? Is the above ground "J" vent behind the spa a venturi vent as well? That would support your suspicion of 2 venturi openings! So are you saying that I do not need a blower and that the air bubbles should work on hydralic vacuum? That would be great because we do not use the blower because it is too over powering! Should I try capping the J vent and the Blower pipe, or will that create additional problems?
    This very slow loss of prime ONLY in "spa mode" suggests that the problem lies in the water flow in that mode only, and might be related to the plumbing. One of my best builders (now) went through an initial phase of most all of his elevated, spillover spa configurations lost water from the spa...it was a plumbing error, easily solved.

    One final question...when in "spa mode" with the pump OFF, is there any water loss in the spa overnight? [/quote:2znds55s]
    It does not ever lose water running or not.
    Thanks for the input!! Not only could this fix the problem but also provide a more enjoyable spa experience!

  11. Back To Top    #11

    Re: Hot Tub losing prime after 30-40 minutes?

    I just pulled my Baker spa order form and it was ordered indicating that we will be using a "stand alone air blower system (not tied to jets, recomended for Florida)". It also has no special note "No Air buttons"? I am not exactly sure what they mean by air buttons, but I do have 7 round half dollar size buttons that blow air when the blower is on. The "no air buttons" does not make sense, if the blower is not tied to the jets (and it is not)it has to come out somewhere???
    As it stands, if I understand this correctly I have 2 air systems??? 1) a stand alone air blower that blows through air buttons only NOT water jets. and 2) a NON WORKING venturi air system that should blow air thru the jets that does not work because it is either installed wrong with 2 vents or some other reason....
    Is this correct? If so, being my first spa I was not aware air should come throught the jets or that the knobs on the spa where non functioning air jet controls valves?

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    launboy's Avatar
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    Re: Hot Tub losing prime after 30-40 minutes?

    Yes, you should have venturi air coming out of the jets and those knobs you are refering to are probably to control that air.

    The Air Buttons they are probably talking about are used to control the blower motor and sometimes the pump. It's an alternative to having electric buttons right by the spa.
    Is there a chance you could snap a pic or two of the spa and equip. pad?

    Thanks,
    Adam
    18' x 42" Intex Easyset Pool, with 16' x 52" deep end in the middle. Approx. 5500 Gal.
    Hayward Power-Flo LX 1 HP, 100# Jacuzzi Brand Sand Filter(Piped underground so it looks nice) 8)
    3 - 2' x 20' Solar Pool Heater Panels(roof mounted)
    Goin' on 9 summers...NOBODY thought it would last this long.
    Buried Portable Spa sharing pumps and water with pool (Almost complete project)

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    Re: Hot Tub losing prime after 30-40 minutes?

    These are the pics. I covered the J vent with duck tape, but it did not change anything...




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    Re: Hot Tub losing prime after 30-40 minutes?

    A thought on the "No air buttons" could that mean "No. (#) air buttons"? If it should have a "7" next to it. (Adam's theory was ruined by the pic showing the in spa control pad )

    Nice to see you're Virginia Graeme Baker compliant (I think you are with the vacuum kill on the suction line, but what's the open hole in the bottom of the spa?? )

    Still trying to noodle out why the gurgling and loss of prime after 30 - 40 min and with heater - I'll be seeing some of my co-workers this PM (for a wake ) I'll see if they can proffer any theories.
    Luv& Luk
    -Ted

    Having done construction and service for 4 pool companies in 4 states starting in 1988, what I know about pools could fill a couple of books - what I don't know could fill a couple of libraries :-D

    POOL SCHOOL, TF Testkits, Jason's Pool Calculator, CYA vs. cl chart, (Just a few DARNED handy links!)

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    launboy's Avatar
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    Re: Hot Tub losing prime after 30-40 minutes?

    Wait, how was my theory ruined? There's no Air buttons in the control. It looks like elecrtic buttons for control(bottom center control) and twist open venturi air controls(left side). Where are the air buttons, unless the ones on the left are buttons and not twist caps.

    P.S. What is the canister like thing with the guage on the suction side of the pump in the first picture? Is this the safety vacuum relief thing? Could this be causing the bubbles and loss of prime? Not sure hoe that has anything to so with the heater though.

    Adam
    18' x 42" Intex Easyset Pool, with 16' x 52" deep end in the middle. Approx. 5500 Gal.
    Hayward Power-Flo LX 1 HP, 100# Jacuzzi Brand Sand Filter(Piped underground so it looks nice) 8)
    3 - 2' x 20' Solar Pool Heater Panels(roof mounted)
    Goin' on 9 summers...NOBODY thought it would last this long.
    Buried Portable Spa sharing pumps and water with pool (Almost complete project)

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    Re: Hot Tub losing prime after 30-40 minutes?

    The Vac Alert on the suction side may be the issue. With the pump on in spa mode, put a plastic bag over the gray end up top (to the right of the pressure gauge in the pic) and see if the bag is drawn into it. If so, you'll need to have it recalibrated for spa use. The suction pressure from your spa plumbing is probably much higher than your pool's, and if the vac-alert is calibrated for the pool this is the problem you'll get.

    Unfortunately the vac alert alone doesn't mean you're VGB compliant, but since this is only for your personal use you're all set.

  17. Back To Top    #17

    I have found he problem!!!

    launboy mentioned the pool flows better than the spa so to test that I used spishex idea of the plastic bag, but instead I placed it over one of the 2 spa intakes. Within 5 seconds the vent tube started to gurgle and the pump started to take in air and lose prime just like the problem i am having. (but At a much faster rate than it normally losses prime) I guess now my question is....how do I add more intake volume from the spa? or is there a way to increase the threshold of when the U & J vent allow air into the system(the gurgling)??

    On a side note, I did determine the venturi air that comes out of the jets does work, but only when the blower motor is on! This sucks, I would like to be able to operate them independently of the blower motor!

    Thank you everyone for your input!!!

  18. Back To Top    #18
    spishex's Avatar
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    Re: I have found he problem!!!

    Quote Originally Posted by msw777
    launboy mentioned the pool flows better than the spa so to test that I used spishex idea of the plastic bag, but instead I placed it over one of the 2 spa intakes. Within 5 seconds the vent tube started to gurgle and the pump started to take in air and lose prime just like the problem i am having.
    You covered up one of the intakes in the tub itself?? That could easily cause it to cavitate and spit air, in which case you'd see all the same symptoms. Doesn't necessarily mean you don't have sufficient flow to the pump during normal operation. Was there any suction on the bag at the vac alert?

  19. Back To Top    #19

    Re: Hot Tub losing prime after 30-40 minutes?

    Quote Originally Posted by waste
    A thought on the "No air buttons" could that mean "No. (#) air buttons"? If it should have a "7" next to it. (Adam's theory was ruined by the pic showing the in spa control pad )

    Nice to see you're Virginia Graeme Baker compliant (I think you are with the vacuum kill on the suction line, but what's the open hole in the bottom of the spa?? )
    It is a pool return for a fountain.
    Still trying to noodle out why the gurgling and loss of prime after 30 - 40 min and with heater - I'll be seeing some of my co-workers this PM (for a wake ) I'll see if they can proffer any theories.

  20. Back To Top    #20

    Re: I have found he problem!!!

    Quote Originally Posted by spishex
    Quote Originally Posted by msw777
    launboy mentioned the pool flows better than the spa so to test that I used spishex idea of the plastic bag, but instead I placed it over one of the 2 spa intakes. Within 5 seconds the vent tube started to gurgle and the pump started to take in air and lose prime just like the problem i am having.
    You covered up one of the intakes in the tub itself?? That could easily cause it to cavitate and spit air, in which case you'd see all the same symptoms. Doesn't necessarily mean you don't have sufficient flow to the pump during normal operation. Was there any suction on the bag at the vac alert?
    part of my problem has been I can not replicate the problem. This is the first time I was able to get it lose prime in the exact same way. The vac alert does seem to have any suction and I do not have any air that i can see in the line from the clear pump cover.

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