Air build up in filter?

[r5ran]

Hello, I have a 2008 Hot Springs Vanguard that has served me well through the years, but I have been fighting a very intermittent issue recently that I would appreciate some help with.

Starting about 2-3 years ago, sometimes the tub would just stop, no circulation pump, nothing on the control panel would light or buttons would operate, except for the red power light would just blink. Resetting the power to the tub would clear this every time. I would have no further issues until maybe months later it would occur again. Sometimes it would be 6-9 months between occurrences, sometimes it could just be a few weeks. It did not seem to follow any pattern either, sometimes it would happen while in use, other times it would occur just sitting unused. I was able to check the logic board once while in the error state, and I think (this was over a year ago and have not been able to check it lately due to weather) all lights were off except for a flashing red D17(?) LED that coincided with the blinking red power light on the front panel. 

I realize the flashing red led is the high limit thermistor and usually the sign of a dirty filter. I did replace all the filters (with both aftermarket then HS brand) but still the problem returned. Since all the components were still the originals, I went ahead and replaced the heater (with an OEM Watkins heater), the control and high limit thermistors and the circulation pump. It seemed to be OK after that for quite a while, but since it can go months without an issue, it's impossible to say for certain. To my surprise, a couple weeks ago, the problem did return. Again resetting power cleared the error and the tub has been operating fine since.

However in checking things out before I reset power, I did discover one thing that may be significant. When I removed the cap that holds down the circulation pump filter, a massive air bubble was released.  I checked the other filter caps, and a few tiny bubbles came out, but nothing like the air trapped in the circulation filter. So now the tub has been operating without problems since then, but I have been checking the air inside the circ. pump filter cap every few days, and have discovered that air seems to be slowly building up inside of it. I am wondering if this air bubble is building up inside the circ. filter, eventually getting large enough to create an air lock and actually starve the circulation pump for water, which could cause the high limit thermistor to trip? Very similar to a clogged filter. 

Note the filter was just replaced a few weeks ago (when I had the recent error), and when I reset power after the error, I do not get any type of air being released from the plumbing, and I do keep the waterfall feature on slightly which is suppose to allow any air buildup to be released.

So my questions are: -

Is this air build up possibly the root cause of my issue, or am I totally lost?    - Is this type of air build up normal? (I don't remember noticing this in the past)    - What can be causing this air to build up, as since there is vacuum inside the filter, it would seem any air would be drawn into the circulation pump. 

Thank you in advance for any suggestions on this. Randy

[RDspaguy]

It could be. I can't say I've ever run into this myself, but any air in the filter could get pulled into the circ pump and cause a flow restriction. Where that air is coming from is the question. Is the water below the top of the filter? Is the cap tight against the filter?

[r5ran]

Hello, and thanks again for your help. Sorry for the delay, I wanted to monitor and try a few things before writing back.

First, to answer your questions. Water level is always well above the filter, so no air could possibly be entering that way. Also, I have tried having the filter cap loose or tight, and it really had no effect on it.

I have been removing and checking for air inside the circulation pump cap periodically and have noticed, as before, (Note, I always turn the cap upside down before installing to release any air trapped) that after a day or two, I do have a small amount of air built up inside the cap. If I let it go a week or so, the amount of air continues to increase and the air bubble is larger than compared to when I check every few days.

So air is building up inside the circulation filter, for sure. I do think this is my root cause, not a bad thermistor  heater or pump. When this air restricts flow or an air bubble actually gets into the heater, it sets off the high limit thermistor and the blinking red light.

I don't really remember this air build up in years past, but it's hard to say for sure. I know their are a LOT of HS owners out there that read this forum, so can any other HS owners PLEASE pipe in and let me know if they ever have any air inside their circulation filter cap when they remove it? That would be helpful.

But did notice a key thing the other day that I think confirms this is definitely an air issue. While I was in the tub and playing around with the cap/filter, all of a sudden a large air bubble came up from the floor drain...everything seemed OK initially, as the circulation pump and ozonator bubbles continued to flow. However, the rest of the tub was dead (control panel, jet pumps, etc...) and the dreaded red light was flashing. Resetting power again brought it all back to normal. Sorry, so was unable to remove access panel to check circuit board LEDS at the time.

So I guess were back to the original question,  where is this air entering the system, and how could it be backflowing and collecting in the filter? I would think that since the inside of the filter is a vacuum, that any air should flow with the water, through the pump/heater and out the floor drain....

Any thoughts are appreciated. Randy

[RDspaguy]

Yeah, it's a very strange situation. Kinda defies logic. I wish I had a simple answer for you.

[r5ran]

Thanks again. I was hoping that some other HS owners would chime in and let us know if they ever get similar air build up in their circulation filter, but so far no responses. Maybe I'll start a new thread on this and get some one's attention? Thanks, Randy

 

[RDspaguy]

I've been fixing spas for 26 years and have owned many watkins tubs over the years. What you describe is not normal. You can get an air bubble under the cap portion, but any lower and it will clear from water flow. An air bubble in the pump will keep it from running, but a bit of air at a time will just flow through the system. For it to gather enough air in the filter to stop flow it would have to create a suction vortex in the filter that reaches air. 

I suspect you have another issue, such as a failing pump or thermistor. But that's just a guess. Without being there and able to cause the issue in a repeatable fashion it's just guesswork.

[RyanN]

I have a similar issue with my tropic seas and can’t figure out how it is getting enough air in the system that is running constantly to cause an airlock. It seems inconsistent.  Any advice is appreciated.

[lovemytoystoo]

I have a 2006 Hot Spring Vista SS with the exact same problem but with even more air build-up in the filters. I just replaced all the filters with brand new Watkins Tri-X filters and it didn't solve the issue. The air build-up seems to be related to a constant tripping of the heater circuit. The spa will heat to temp and randomly trip off after a few days. Just before draining the spa to check on a few things, I noticed the circulating pump was very warm to the touch. There is constant flow going into the filter well so it is working but I don't know if there might be a problem with the impeller so I'm going to remove it to see if there are any visible issues. I thought air might be sucked into the system from bad o-rings on the diverter valves but the problem wasn't resolved after installing new o-rings. 

[Soaking]

I am having same issue as you describe on a 2006 hot springs jet setter. Did you figure out the cause for yours?