DE flowing back into pump

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J

joshf

Gold Supporter
May 1, 2019
47
Austin, TX
Pool Size
17000
Surface
Plaster
Chlorine
Salt Water Generator
SWG Type
CircuPool RJ-45
I never noticed this my first 3 years of pool ownership, but starting near the end of last season I noticed that under certain conditions, DE would flow back into the pump, or if I had to the Polaris cleaner valve open, it would flow back into the pool.
I'm not sure of all of the circumstances that cause it, but I noticed one today. If I open the pump skimmer lid, the water level in the pump will drop. But if I then open the filter pressure release valve, (I was trying to drain the pump to test out necessary prime speed for new VSP), the pump quickly filled up with cloudy DE water. Is this "normal", and I had just never done these steps before?
I wonder if it has to do with the new pipes I put in a couple years ago to mount the SWCG vertically. Does the extra rise contribute to pushing the water back toward the pump?
Is this something I should get a check valve for?
Any insight on if this is a problem, or how to address would be appreciated. I've had a lot of problems with DE in the pool lately and have inspected the filter elements closely and don't find any rips. Wondering if this is related.
 
What happens when you open the air relief valve while the pump is running? You should have water shooting out of the valve. The only time you might have water flowing back into the pump as if the pump is not running. This would indicate a leak somewhere in the plumbing system.
 
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You're right, it only happens when the pump is not running. I mistakenly tried that to get the water to drain more, to test the priming.

But when I open the air relief valve while the pump is running, I do get milky (DE) water shooting out the valve. That seems like a new symptom - the first few years I dont remember DE shooting out. Is that "normal"?
 
Having a Pentair filter myself, I can tell you the most common failure point is the air relief valve. There are a couple of o-rings in there that fail over time. Try this; turn off the pump and put your ear up next to the air relief valve. If you hear a hissing it's likely the o-rings need to be replaced.
 
Keep checking your system for hissing sounds. Something is not holding pressure as it should. The next place I would check is the MPV, but knowing nothing about them, I can't provide much guidance. Maybe @Texas Splash can provide some assistance.
 
I have noticed a new gurgling sound around the MPV after installing my new VSP. I attributed it to lower water levels running at lower speed. Is that normal?

It’s possible the noise was there before but I didn’t notice because the old single speed pump was so loud.
 
JamesW said:
For a DE filter, you should always have a check valve between the pump and the filter.
Click to expand...
Interesting, I hadn’t heard that. I inherited my system with the DE filter already installed.
Is there a recommendation for a check valve that works well with a VSP? A quick search brought me to this one, but it says it require 5psi for water to flow. My VSP running at 1500rpm shows around 4psi in the filter valve.
 

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joshf said:
But if I then open the filter pressure release valve, the pump quickly filled up with cloudy DE water. Is this "normal",
Click to expand...
It's normal for the pump pot to fill with water when the lid is removed and you open the system somewhere (i.e. air relief valve). Mine does that as well and it helps me to fill the pot if I emptied it for some reason. In your case with DE and no check valve between the pump and filter, some of that will flow backwards when you do that.

But the pot shouldn't drain empty just because you removed the lid and I don't think the SWG install is to blame just yet. I tend to agree with @Rancho Cost-a-Lotta that you seem to have an air leak somewhere. Odd thing is that just like the example above with removing the pump lid and opening the air relief to fill the pot, if you had an air leak somewhere, I would think the pot will fill right away when you removed the lid. :scratch:

At this point I wouldn't rule anything out. Perhaps check the 3-way valve (and handle) O-rings. That's fairly easy to do. If you haven't inspected the spider gasket in a while, you can pull the top off the MPV and inspect that as well. Not a whole lot else on your pad with such a simple set up.
 
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