Very Inconsistent and poor pressure in spa jets
- Thread starter golfingff
- Start date
- May 3, 2007
- 17,020
- Pool Size
- 20000
- Surface
- Plaster
- Chlorine
- Salt Water Generator
- SWG Type
- Hayward Aqua Rite (T-15)
Based upon the information that you gave me, my hyrdaulics model estimates the following:
Intelliflo at full speed with filter and heater:
82.5 GPM @ 82.4' of head, 24.5 filter PSI
16.5 GPM/jet @ 8.3 PSI/jet
Whisperflo:
91 GPM @ 71' of head
18.2 GPM/jet @ 10.2 PSI/jet
Note that a 10 PSI jet tends to feel weak, a 15 PSI moderate and a 20 PSI jet feels strong. A strong 7/16" jet runs at about 25 GPM @ 20 PSI which would require 125 GPM out of each pump.
There may still be a clog somewhere in the system which may be why the jets do not feel equally strong but given the model predicts the filter pressure pretty closely, my guess is that it is operating as designed. The problem is with the design.
First the pipe size limits the flow rate through the jets. At 125 GPM, the PB should have been using at least 2.5" plumbing and preferably 3" plumbing for 100' runs. Plus spa jets should not go through the filter/heater. A separate circulation loop should be used for that and have dedicated pumps for just the spa jets. Using 2.5" plumbing with dedicated 2 HP full rated pumps (no filter/heater), would have delivered close to 13 PSI and 3" pipe would have delivered over 15 PSI per jet or a more moderate feeling jet.
However, there may be simple fix. Some spa jets come in different sizes so if you can replace the nozzle with a 3/8" version or find an insert reducer, that will increase the pressure of the jets and make then feel stronger.
For the Intelliflo, the new operating point would be:
76 GPM @ 84.5' of head
15.2 GPM/jet @ 13.2 PSI/jet
So even though there is less flow rate through the jet, there is more pressure loss at the jet instead of the plumbing so the jet will feel stronger.
Intelliflo at full speed with filter and heater:
82.5 GPM @ 82.4' of head, 24.5 filter PSI
16.5 GPM/jet @ 8.3 PSI/jet
Whisperflo:
91 GPM @ 71' of head
18.2 GPM/jet @ 10.2 PSI/jet
Note that a 10 PSI jet tends to feel weak, a 15 PSI moderate and a 20 PSI jet feels strong. A strong 7/16" jet runs at about 25 GPM @ 20 PSI which would require 125 GPM out of each pump.
There may still be a clog somewhere in the system which may be why the jets do not feel equally strong but given the model predicts the filter pressure pretty closely, my guess is that it is operating as designed. The problem is with the design.
First the pipe size limits the flow rate through the jets. At 125 GPM, the PB should have been using at least 2.5" plumbing and preferably 3" plumbing for 100' runs. Plus spa jets should not go through the filter/heater. A separate circulation loop should be used for that and have dedicated pumps for just the spa jets. Using 2.5" plumbing with dedicated 2 HP full rated pumps (no filter/heater), would have delivered close to 13 PSI and 3" pipe would have delivered over 15 PSI per jet or a more moderate feeling jet.
However, there may be simple fix. Some spa jets come in different sizes so if you can replace the nozzle with a 3/8" version or find an insert reducer, that will increase the pressure of the jets and make then feel stronger.
For the Intelliflo, the new operating point would be:
76 GPM @ 84.5' of head
15.2 GPM/jet @ 13.2 PSI/jet
So even though there is less flow rate through the jet, there is more pressure loss at the jet instead of the plumbing so the jet will feel stronger.
Ok. Makes sense to me. So it sounds like were kind of SOL as the design can't really be changed at this point without digging everything all up and basically re-plumbing everything. I will look for any blockages, as it does seem that the jets should be equally poor instead of all the pressure out of 2 unless that is by poor design as well? I will also check into the smaller jets as well and see if that helps. Thanks for your time with all the figures and replies. Much appreciated
Couple other questions I had
1. Do you think that there is a possibility that the check valve he installed between the pump and filter could be causing an issue at all?
2. Do you think that the depth that the jet has been installed inside of the pipe itself could make each jet vary in pressure? I have noticed that there are differences as some are with a couple inches of the pipe end and some are back about 6-8"? Also, looking inside of them some have the air orifice on the top and some on the bottom? Does this stuff make any difference? Thanks again
1. Do you think that there is a possibility that the check valve he installed between the pump and filter could be causing an issue at all?
2. Do you think that the depth that the jet has been installed inside of the pipe itself could make each jet vary in pressure? I have noticed that there are differences as some are with a couple inches of the pipe end and some are back about 6-8"? Also, looking inside of them some have the air orifice on the top and some on the bottom? Does this stuff make any difference? Thanks again
- May 3, 2007
- 17,020
- Pool Size
- 20000
- Surface
- Plaster
- Chlorine
- Salt Water Generator
- SWG Type
- Hayward Aqua Rite (T-15)
1. If it was restricting flow at all, the filter pressure should be much lower than it is. The filter pressure seems to be consistent with the plumbing you have. One way to know for sure is to measure the pump pressure at the return side drain plug. If it is more than 2 PSI higher than the filter pressure, then it could be due to a faulty check valve.
2. Yes, not only the depth in the pipe but jets closer to the surface tend to be stronger than ones deeper in the spa.
2b. Normally, the venturi air pipe is plumbed in the upward position but it should work either way as long as the flow rate is high enough to remove the water out of the air pipe.
If one of the jets is clogged, it may actually suck in some water because of the other jets attempting to suck in air from their air pipes.
2. Yes, not only the depth in the pipe but jets closer to the surface tend to be stronger than ones deeper in the spa.
2b. Normally, the venturi air pipe is plumbed in the upward position but it should work either way as long as the flow rate is high enough to remove the water out of the air pipe.
If one of the jets is clogged, it may actually suck in some water because of the other jets attempting to suck in air from their air pipes.
Ok great. That makes sense to me. That might be the reason that we are getting suction on a couple of our jets. I will look for any kind of blockages in those particular jets. Also, what is your opinion on getting rid of one of my pumps and running two suction lines to one pump due to the lack of pipe size? I know it's not even close to being the same as the larger diameter but it has to be better than just one. Do you think this might help out? What you said also explains why the jets that were plumbed for our lower legs are not very strong either. It sounds like we are just very restricted because of our pipe size due to poor design. Thanks again
- May 3, 2007
- 17,020
- Pool Size
- 20000
- Surface
- Plaster
- Chlorine
- Salt Water Generator
- SWG Type
- Hayward Aqua Rite (T-15)
You will have a worse situation because one pump cannot provide enough flow rate for all of the jets. 10 jets require 200-250 GPM total which neither pump can produce with even no head loss. You are better off with the configuration you have, but you might consider new nozzles which do not require as much flow rate.
Mark- Just wondering what you think of this statement that I got from a Pentair Pool Forum. I know that you said it would make it worse but wanted to see if this reply post made any sense at all to you? Thanks, Jake
"So without even running any calculations I can tell you that at that distance if you expect to get good flow you would need 4" suction, however you do not need that much flow to handle 5 jets for each pump. We typically plan for about 20gpm for a jet, but they usually specify as needing 10gpm. a VS pump with 4" suction, 3" return would be able to give you 100-120gpm. So maybe a bit low to handle all ten jets, but you would not be unhappy with the pressure. (those are general volumes without knowing the exact system, elevation changes, fittings, valves, etc)
You need to get someone who understands Hydraulics to review the system.
I would start with the idea of removing a pump, and sharing that suction with you vs pump (2-2" pipes are not even close to 1-4" but it is a start.) If you try to run the pump at full speed the velocity will be extremely high, potentially unsafe for the swimmer, against code, and extremely inefficient.
Start by reading an old blog post of mine to get you into the mind set of how to use a VS or VF pump. http://poolfyi.com/profiles/blogs/why-t ... s-the-only.
With automation, you can use the VS pump to do multiple jobs but changing speeds and valves, maybe allowing you to share suction to decrease velocity, increase flow, and make you happy with the jet output.
You should also make a quick check of the jet orifice. Even the smallest debris or stone will cause the jet to even suck water sometimes."
"So without even running any calculations I can tell you that at that distance if you expect to get good flow you would need 4" suction, however you do not need that much flow to handle 5 jets for each pump. We typically plan for about 20gpm for a jet, but they usually specify as needing 10gpm. a VS pump with 4" suction, 3" return would be able to give you 100-120gpm. So maybe a bit low to handle all ten jets, but you would not be unhappy with the pressure. (those are general volumes without knowing the exact system, elevation changes, fittings, valves, etc)
You need to get someone who understands Hydraulics to review the system.
I would start with the idea of removing a pump, and sharing that suction with you vs pump (2-2" pipes are not even close to 1-4" but it is a start.) If you try to run the pump at full speed the velocity will be extremely high, potentially unsafe for the swimmer, against code, and extremely inefficient.
Start by reading an old blog post of mine to get you into the mind set of how to use a VS or VF pump. http://poolfyi.com/profiles/blogs/why-t ... s-the-only.
With automation, you can use the VS pump to do multiple jobs but changing speeds and valves, maybe allowing you to share suction to decrease velocity, increase flow, and make you happy with the jet output.
You should also make a quick check of the jet orifice. Even the smallest debris or stone will cause the jet to even suck water sometimes."
- May 3, 2007
- 17,020
- Pool Size
- 20000
- Surface
- Plaster
- Chlorine
- Salt Water Generator
- SWG Type
- Hayward Aqua Rite (T-15)
With 7/16" jets, you should have 20 GPM/jet and you would be disappointed with 10 GPM since that is less than what you have now. BTW, this is not just my opinion, this is Waterway recommends for their 7/16" jets.
This will result in a higher flow rate for the Intelliflo but since you are removing the Whisperflo, that flow rate goes away. So the total flow rate of the single pump on two pipes will still be less than two pumps on two pipes.
I can actually predict the flow rate in each configuration but looking back at your post I wanted to make sure that I was reading correctly on two items.
Filter pressure is 25 PSI?
Is the pad 3-5' above the water level or below the spa water level?
Things I think I see:
2" plumbing for the suction is inadequate, especially for a 100' run. 2.5" for the 2 HP and 3" for the Intelliflo should have been used.
Multiple levels for the return jets will yield unequal pressure at the jets where the deep jets get less.
Did I see the air loop go under a water loop it's related to? Air loops over go over the water loop it's related to.
Any chance you could mark up the jets so we know which loop has which jets?
Is there more than one blower?
Scott
2" plumbing for the suction is inadequate, especially for a 100' run. 2.5" for the 2 HP and 3" for the Intelliflo should have been used.
Multiple levels for the return jets will yield unequal pressure at the jets where the deep jets get less.
Did I see the air loop go under a water loop it's related to? Air loops over go over the water loop it's related to.
Any chance you could mark up the jets so we know which loop has which jets?
Is there more than one blower?
Scott
Thanks again Mark. I am working on getting some of the 3/8" jets to try that as you suggested. Yes the filter pressure is 25psi and the equipment is approx 3-5' below the spa level. Once again, I really appreciate all of your professional opinion here. Scott, I will work on your questions and see if I can find a way to mark the jets for each line. Thanks
Scott-
Seems as though all of you agree that the size of pipe that the builder used is inadequate. I am kind of out of luck on that now as everything would have to be torn apart and done all over. My guess is since he was (unfortunately) already paid that this isn't going to happen. Interesting point on the jets though what about inconsistencies with jets that are on the same level? Would this also affect them as well? Only one blower on the system. I am going to try and figure out a way to let you know which jets are on which lines.
Seems as though all of you agree that the size of pipe that the builder used is inadequate. I am kind of out of luck on that now as everything would have to be torn apart and done all over. My guess is since he was (unfortunately) already paid that this isn't going to happen. Interesting point on the jets though what about inconsistencies with jets that are on the same level? Would this also affect them as well? Only one blower on the system. I am going to try and figure out a way to let you know which jets are on which lines.
- May 3, 2007
- 17,020
- Pool Size
- 20000
- Surface
- Plaster
- Chlorine
- Salt Water Generator
- SWG Type
- Hayward Aqua Rite (T-15)
So I made a couple of adjustments to the model but here are the different scenarios and the results:
Current setup with 7/16" jets
Intelliflo w/filter/heater: 85 GPM @ 82' head, 17 GPM/Jet, 9 PSI/Jet, 36 ft/sec/jet
Whisperflo: 94 GPM @ 69' head, 19 GPM/Jet, 11 PSI/Jet, 40 ft/sec/jet
Remove WHisperflo and use two pipes on the Intelliflo
Intelliflo w/filter/heater: 107 GPM @ 72' head, 11 GPM/Jet, 3.5 PSI/Jet, 23 ft/sec/jet
Note that with the single pump, flow rate does improve but not enough to compensate for a missing pump.
Setup with 3/8" jets
Intelliflo w/filter/heater: 78 GPM @ 84' head, 16 GPM/Jet, 14 PSI/Jet, 45 ft/sec/jet
Whisperflo: 85 GPM @ 74' head, 17 GPM/Jet, 16 PSI/Jet, 49 ft/sec/jet
Note that the Jet PSI and exit velocity are much higher for the 3/8" jet which will make the jet feel stronger.
However, if there is still an imbalance between the jets, then it is probable that the spa plumbing around the spa is causing the problem. Could be debris or the way the PB did the plumbing. The 2" pipe tells us that he obviously did not know what he was doing.
One final note is that I had to add a lot of head loss to the suction side in order to bring down the filter pressure to 25 PSI. So there could still be some blockage in the suction line.
Current setup with 7/16" jets
Intelliflo w/filter/heater: 85 GPM @ 82' head, 17 GPM/Jet, 9 PSI/Jet, 36 ft/sec/jet
Whisperflo: 94 GPM @ 69' head, 19 GPM/Jet, 11 PSI/Jet, 40 ft/sec/jet
Remove WHisperflo and use two pipes on the Intelliflo
Intelliflo w/filter/heater: 107 GPM @ 72' head, 11 GPM/Jet, 3.5 PSI/Jet, 23 ft/sec/jet
Note that with the single pump, flow rate does improve but not enough to compensate for a missing pump.
Setup with 3/8" jets
Intelliflo w/filter/heater: 78 GPM @ 84' head, 16 GPM/Jet, 14 PSI/Jet, 45 ft/sec/jet
Whisperflo: 85 GPM @ 74' head, 17 GPM/Jet, 16 PSI/Jet, 49 ft/sec/jet
Note that the Jet PSI and exit velocity are much higher for the 3/8" jet which will make the jet feel stronger.
However, if there is still an imbalance between the jets, then it is probable that the spa plumbing around the spa is causing the problem. Could be debris or the way the PB did the plumbing. The 2" pipe tells us that he obviously did not know what he was doing.
One final note is that I had to add a lot of head loss to the suction side in order to bring down the filter pressure to 25 PSI. So there could still be some blockage in the suction line.
Excellent reply. Wish we would have had someone with your knowledge build this thing for us. I would have gladly paid a bit more to have the proper size pipe installed and have the spa operate to it's potential. Very interesting hydraulics numbers that make a lot of sense to me. Any suggestions on how to check for further blockages in the suction line as I have already found 2 of these chunks of plaster (approx golf-ball size) and 2 plastic grocery bags
Attachments
Scott- I'm not sure how much this will help you understand but the jets that are on the 2hp Whisperflo are the 5 that I am showing in these pics. The 4 bottom jets under the waterfall (2 lower back and 2 leg) and the one other jet above the spa light that is shown in the pic. This happens to be the strongest jet of them all and the builder said that it was because it was the first in line?? Don't know why that would matter as I thought they were supposed to be equal pressure if designed/plumbed correctly?
Attachments
- May 3, 2007
- 17,020
- Pool Size
- 20000
- Surface
- Plaster
- Chlorine
- Salt Water Generator
- SWG Type
- Hayward Aqua Rite (T-15)
That is exactly right. If he had looped the jets properly and used large enough pipes, it wouldn't matter where in the line they are.
The depth in the water can make a slight difference but again, if they were plumbed properly, they would be much closer in pressure. The smaller jets can make up some for a bad plumbing job. Although if there is any debris left in the lines, then there isn't much you can do on the return side except remove the nozzles and try to flush them out. You will have bit more pressure if you remove the nozzles one at a time.
As for the suction side blockage, about the only thing you can do is to remove the drain covers and flush the line backwards. You can build up a bit more pressure if you put a hose through the pump basket into the suction pipe and then seal around the hose with a wet rag. A Drain King works well too because it adds a bit of vibration which can help break things up. But given the length of the runs that may not help much either.