Air lock in new filter

aaronsmith

Member
Dec 13, 2018
16
NH
Hello,


I just went from an old Harmsco metal filter 155 sq ft to a larger Pentair Clean and Clear Plus 320 sq ft filter for my hot tubs in hopes they would stay cleaner longer and have had nothing but problems with air getting into the system. I know the Harmsco had the upflow technology that continually pushes the air out of the filter canister through the way they plumbed it inside, but this Pentair does not have this... In response I have installed automatic air vents like you would see on hydronic heating systems on top of the Pentair filter to try and relieve air but they are not reliable and I have found that by doing this it reroutes the internal water flow in the filter, making the water in the filter bypass the filters and go through the internal air relief pipe in the filter instead. I capped this air relief pipe off with a 1/2 PVC cap, which fixed the internal filtration issue, but I am still left with aweful air lock. After one hour of use, the hot tub pump will literally be full of air, zero gpm and psi which will obviously cause major problems to the furnace and pump if not fixed (this happened before and after capping the internal air relief pipe, I honestly don't believe this thing works in my current config). Does anyone have a solution to this or has seen this in the past? I am wondering if upping my pump from 1HP to 1.5HP would help move/push the air out of the filter if I installed that and normalized the internal air relief pipe inside. During high speed on the 1 HP pump I am at 15 psi and during low speed I am at 4-5 psi... I am wondering if the 1 HP pump is undersized for the size filter I have? I know the pressure out of the jets is not great and have been told it should be stronger... Would this fix the air problem too or is there another way to relieve the air lock issue? This just seems crazy as Pentair states these filters are for spa use, but as soon as I run bubbles, the filter cannot keep up with the amount of air going in. Thank you for any help you can provide.
 

Bama Rambler

Mod Squad
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The filter shouldn't be causing this problem. You don't say what spa you have or if the filter is plumbed on the suction or discharge side of the pump?

Can you post a picture of the spa and the plumbing?
 

aaronsmith

Member
Dec 13, 2018
16
NH
This is an older acryllic spa from the 90's used frequently throughout the day in 1 hour increments. I never had a problem with air lock with the Harmsco.

The Spa is:
app 400 gallons
30-40 feet plumbing distance between spa and pump/filter/heater with multiple angles 90's and 45's, one shot flex PVC to 4 jets.
1.5" PVC throughout
Current Flow Rate of 9-10 GPM under low speed
1 HP Pentair Whisperflo 2 Speed 230volt
Pentair Clean and Clear Plus 320
Low Speed PSI= 4-5 PSI
High Speed PSI= 15-20 PSI

Thanks alot for any help
 

Bama Rambler

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Jun 22, 2009
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If you don't run the aeration does the pump basket get air in it? If so then you have a suction side air leak. I think the problem may be in the plumbing and not directly related to the filter.

Do you know if the filter is plumbed on the suction or discharge side of the pump?
 

aaronsmith

Member
Dec 13, 2018
16
NH
I thought this too but the air accumulation only occurs when the high speed and bubbles are running in the hot tub during a session. Under non hot tub use/low speed, there is no air accumulation in the filter, the pump basket is full to the top with water/no air. I believe the bubbles in the water is sending the aerated water into the filter, filling up with air and causing the air lock. Because the hot tub sessions run for 1 hour plus, the air relief setup in the pentair filter cannot keep up? The harmsco had the upflow technology to prevent this air buildup which prevented this. I am just wondering if maybe I increase the HP on the pump and normalize the internal air relief pipe inside the pentair, I can get enough internal pressure to push the air out of the top of the filter and into that air relief pipe inside during low speed and high speed operations but something tells me this isnt going to fix it because the massive accumulation of air in the system occurs only during high speed operation in the 15-20 psi higher GPM... is the after session 4psi 9GPM low speed too low to push this accumulated air out of the filter after? Increasing the HP would also fix the low pressure out of the 4 jets...
 

Jimrahbe

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Jul 7, 2014
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Bedford, TX
Arron,

In theory, the only time you should need to open the air relief valve on the filter is right after it was cleaned and put back together. The only way air will get into the system is from a suction side air leak.. In practice, of course, it does not take much of an air leak to introduce air into the system, and over time it can build up.

Maybe your other filter had a better way to get rid of the air, so you never noticed it before.

Like Dave, I too believe that you have a suction side air leak.. I really doubt that the problem has anything to do with the HP of your pump..

I would check and lube the pump lid O-ring, as well as the two drain plugs and their O-rings.

If there are any valves in front of the pump, they too have seals that can let air in..

Another place for an air leak is the threaded inputs to the pump, which tend to dry out and leak after a few years.

When you shut off the system, does the water in the filter and pump, drain back into the spa?

Thanks,

Jim R.
 

aaronsmith

Member
Dec 13, 2018
16
NH
Yes, the water drains back into the spa after shutting the system off. The pump and filter are both brand new. If it was suction wouldnt this occur all the time and not just during a hot tub session?
 

Jimrahbe

Mod Squad
TFP Expert
LifeTime Supporter
Jul 7, 2014
22,824
Bedford, TX
Arron,

Water should NOT drain back into the spa when you turn the pump off...

Think about what happens when you put your thumb over the end of a straw in a glass of water and then pull the straw out. The water stays in the straw until you take your thumb off, or in our case, open the air relief valve.. Not sure if your modification is causing this drain down or not... :confused:

When running at low speed your pump does not have to "suck" very hard... the less suction the less air that will enter the system, especially if the leak is very small..

If the water drains back into the spa, when you first power on the pump, I suspect there is a slight delay and then giant air bubble are forced through the system and into the spa for about 15 to 30 seconds..

Assuming you can't find an air leak, (which is what I would do first) another option would be to add an electric valve to the air relief on top of the filter, and then use a timer to turn the valve on for a few seconds, once every 15 minutes of pump run time.. to prevent the air from building up..

Thanks,

Jim R.
 

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JamesW

TFP Expert
Mar 2, 2011
27,695
The problem is on the suction side of the pump.

Is the hose bib on the suction new? Maybe it's leaking?

Try capping it with a hose cap to make sure that it's not allowing air into the system.

Have someone turn the pump off from high speed while you check the suction fittings for any leaks.

Are all of the glue joints good?

What is the red on the pipe?

Right when the pump is turned off, you should get a quick burst of pressure that should be able to identify any leaks.

Make sure that all suction valves are open.

Make sure that the lid O-ring is lubricated.

Is there air in the pump when running on high?

What are the suction inlets at the tub? Are they blocked or sucking in air?

Is there a cartridge in the skimmer?

What is the height of the pump suction in relation to the spa water level?

soon as I run bubbles, the filter cannot keep up with the amount of air going in.

What does this mean? Do you have a blower tied into the return line?
 

Bama Rambler

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Thanks for posting the pic. It makes it more clear.

Since the filter is on the discharge of the pump it's not what's causing the pump to lose prime. It could be completely full of air and the pump would still pump as long as the suction had water.

When you changed the filter, did you also change anything on the pump or it's location?
 

aaronsmith

Member
Dec 13, 2018
16
NH
If you don't run the aeration does the pump basket get air in it? If so then you have a suction side air leak. I think the problem may be in the plumbing and not directly related to the filter.

Do you know if the filter is plumbed on the suction or discharge side of the pump?

The system runs fine, filter basket is full of water no problems during normal low speed operation... I only have problems when I run the high speed jets and blower motor ie bubbles... this is aerating the water I believe and the old harmsco was able to push this air out of the filter with its upflow technology... this new pump Pentair doesnt have that and its internal air relief system doesnt work good at all.

As soon as I turn on the high speed, the pump pushes the water great upon windup and I have nice pressure out of the jets and then the pump basket empties and it starts straining to pull enough water and the filter then fills up with air... its almost as through the 1.5" PVC cant keep up with the high speed of the pump ie cavitation? which is either causing the filter to fill up with air or I am simply getting air from the bubbles in the water... its either one or the other or a combination of both... but I am getting air in the system when on high speed now with this new filter.

The filter is plumbed on the discharge/output of the pump.

I have two auto air relief valves on top now of the filter and they help alittle but this doesnt seeem to be reliable, they get stuck because they are under constant pressure fluxuation and water burst... just not what they were meant for.
 

aaronsmith

Member
Dec 13, 2018
16
NH
I would like to agree with you but could it be possible after an hour or more in operation for enough air to be pulled into the filter and then make its way into the pump and plumbing causing this air lock to occur? What if so much air got sucked into the filter that the air eventually made its way into the pump? I've seen it after an hour in high speed operation, then session ends, goes back to low speed and the filter has zero PSI and there is no water in the pump...
 

ajw22

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Jul 21, 2013
28,524
Northern NJ
Pool Size
35000
Surface
Plaster
Chlorine
Salt Water Generator
SWG Type
Pentair Intellichlor IC-60
You have a hose bib and hose attached on the suction line. What is that for?

Check that valve is totally closed and not leaking.
 

aaronsmith

Member
Dec 13, 2018
16
NH
If the water drains back into the spa, when you first power on the pump, I suspect there is a slight delay and then giant air bubble are forced through the system and into the spa for about 15 to 30 seconds..

No, I dont get any air being pushed back into the spa from the filter or pump anymore. That used to happen with the Harmsco. Now it all gets trapped and stuck in this filter... none of it seems to get pushed out anymore.

- - - Updated - - -

You have a hose bib and hose attached on the suction line. What is that for?

Check that valve is totally closed and not leaking.

Thats to fill the tub with water. It does not leak water and has a good seal/brand new, but I could check to see if it could possibly be sucking in air when the high speed is on... Thanks.
 

ajw22

Gold Supporter
TFP Guide
Jul 21, 2013
28,524
Northern NJ
Pool Size
35000
Surface
Plaster
Chlorine
Salt Water Generator
SWG Type
Pentair Intellichlor IC-60
I would remove the hose and cap off the bib.
 

aaronsmith

Member
Dec 13, 2018
16
NH
The problem is on the suction side of the pump.

Is the hose bib on the suction new? Maybe it's leaking? Its new and doesnt leak but I will check.

Try capping it with a hose cap to make sure that it's not allowing air into the system.

Have someone turn the pump off from high speed while you check the suction fittings for any leaks. I dont have any water leaks? Would air still able to penetrate in where water cant?

Are all of the glue joints good? yes

What is the red on the pipe? flourscent tape to prevent tripping

Right when the pump is turned off, you should get a quick burst of pressure that should be able to identify any leaks.

Make sure that all suction valves are open. It is

Make sure that the lid O-ring is lubricated. They are

Is there air in the pump when running on high? Yes

What are the suction inlets at the tub? Are they blocked or sucking in air? There is a suction inlet at the top pulling in water

Is there a cartridge in the skimmer? Yes, a mineral stick and a few bromine tabs in the skimmer basket.

What is the height of the pump suction in relation to the spa water level? The pump is below the water level of the spa water



What does this mean? Do you have a blower tied into the return line?
I dont think so, I hope not. I have a blower motor blowing air into the system and it is tied into the high speed operation, such that high speed is only operational when the blower motor and bubbles are running. The blower has its own lines running to the tub.
 

JamesW

TFP Expert
Mar 2, 2011
27,695
If the pump runs on high speed with the blower off, what happens?

What suction ports do you have in the hot tub?

If you have a skimmer, the weir might be sticking and blocking the flow of water.

Check the skimmer while the pump is on high to see if the skimmer is running dry.

Is there a cartridge in the skimmer?
 

aaronsmith

Member
Dec 13, 2018
16
NH
If the pump runs on high speed with the blower off, what happens?

What suction ports do you have in the hot tub?

If you have a skimmer, the weir might be sticking and blocking the flow of water.

Check the skimmer while the pump is on high to see if the skimmer is running dry.

Is there a cartridge in the skimmer?

I tried that today, with the blower off the high speed turns off too. They are wired together it seems. I will troubleshoot more on this. Seems high speed and blower motor operation are somehow wire/ linked togther.

I have the suction at the top ie skimmer and one at the bottom in the tub.

I will take the weir out and see if this helps at all... it almost seems like on high speed the pump is thirsting for makeup water... like it cant get enough... could there possibly be a slight clog somewhere?

What do you mean by a cartridge?
 

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