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Thread: Nautilus FNS building pressure

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    Nautilus FNS building pressure

    Hey! Having a rough time getting my pool up and running this year. We purchased our home last fall from my parents, who hadn't opened the pool in 2 years Needless to say, it was a swamp. With a lot of bleach I've been able to get the pool to a point where it's cloudy blue - a big improvement from black! However, I'm having issues with my filter building up pressure. Lately I've been noticing that the filter (Nautilus FNS 36) pressure climbs from around 10 to about 30 after only a few minutes of filtering. The jets completely stop putting out water. I backwash it, but the water coming out is clear. After the backwash, the pressure is normal again, but quickly jumps back.

    Yesterday I took apart the entire filter and cleaned the grids one by one. They were pretty bad. Today I opened up the filter expecting them to look the same as yesterday, but they actually look pretty good. Good enough that the backwash should be taking care of it, but it's not. I'm getting frustrated and my water level is dropping like crazy from all the backwashing! Any thoughts?

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    Mod Squad Bama Rambler's Avatar
    Join Date
    Jun 2009
    SouthWest Alabama

    Re: Nautilus FNS building pressure

    You may need to soak the grids in some automatic dishwasher detergent solution. That may help your situation.
    Dave J. TFP Moderator
    24' x 52" Round AGP. 2hp/¼hp SPL Power-Flo 2-speed pump. 200sqft Waterway Cartridge Filter. 45MHP2(3GPD) Stenner Peristaltic Pump
    Pool School ----- Pool Math ----- TF-Test Kit

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    Re: Nautilus FNS building pressure

    I thought about that too after some more reading. However, I should also mention that these are brand new filter grids. When I opened the pool this year, I discovered that the old grids had been left out in the sun and were completely deteriorated. The new grids have only been in for a week. Could they have gotten that dirty that fast? Even with me hosing them off and backwashing?

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    Re: Nautilus FNS building pressure

    Ah ha! So as it turns out, I probably should have done some more reading before jumping into this. Considering the state of my pool (really really green), I had convinced myself that running the filter without D.E. would "get the big stuff out" without wasting D.E. (for the fine stuff). After searching around a little on TFP forums, I found that running a D.E. filter without D.E. is NOT a good idea. My understanding is that without D.E. to protect them, the grids basically become impacted - making the pressure jump. Oh well, lesson learned. I cleaned the grids off real good by hand (not just a backwash), mixed a nice big slurry of D.E., turned on the pump and immediately added the required amount of D.E. to the skimmer. Pressure has been stable for about an hour now. Good flow out of the jets. I feel like an idiot! Figured I'd share my experience for anyone else out there! Don't do what I did.

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