Harmsco 905 cartridge retainer nut for TF and TC series filtersHarmsco Cartridge Retainer Nut In stock$2899
Harmsco 905 cartridge retainer nut for TF and TC series filters
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Harmsco Cartridge Retainer Nut

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$2899
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Quick overview

  • Harmsco part 905 Also referenced as HRM905 in Harmsco parts listings.
  • Wide fitment Listed for the TF50, TF75, TF100 and TF150, and the 50TC, 75TC, 100TC and 150TC.
  • Holds the cartridge The retainer nut is what clamps the cartridge in position inside the housing.
  • Bypass risk A cracked or missing nut lets the cartridge lift, and unfiltered water then runs straight past it.
  • Replaced during service The nut is handled every time the cartridge comes out, which is exactly why it wears and cracks.
  • Small part, whole filter The housing cannot do its job without it, so it is worth having a spare on the shelf.
Full description and specifications ↓

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Product details

The Harmsco 905 is the replacement cartridge retainer nut for the TF and TC series cartridge filters. It is listed for the TF50, TF75, TF100 and TF150, and for the 50TC, 75TC, 100TC and 150TC. It also appears as HRM905 in Harmsco parts listings.

What it does

The retainer nut clamps the cartridge down inside the housing. That clamping is what forces every gallon through the media rather than around the outside of it. When the nut cracks, strips or goes missing, the cartridge lifts under flow and the filter quietly bypasses, so the water stops clearing even though nothing appears to be broken.

Why it wears out

This is a part that gets handled at every service. It comes off for each cartridge clean and goes back on afterward, and repeated cycles of that eventually take the threads or split the body. Keeping a spare with your filter cartridges means a routine clean never turns into an unplanned trip for parts.

Specifications
Brand Harmsco
Manufacturer part number 905
Also listed as HRM905
Type Cartridge retainer nut
Fits Harmsco TF50, TF75, TF100, TF150, 50TC, 75TC, 100TC, 150TC cartridge filters
Shipping weight 0.35 lb
Ships Parcel

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Customer reviews

Questions and answers

What people ask about this product, answered by our pool techs.

Which filters does this fit?
The Harmsco TF50, TF75, TF100 and TF150, and the 50TC, 75TC, 100TC and 150TC cartridge filters.
Is the part number 905 or HRM905?
Both refer to the same part. Harmsco lists it as 905, and it also appears as HRM905 in parts listings.
What does the retainer nut do?
It clamps the cartridge in position inside the filter housing so water is forced through the media instead of around it.
Why would I need a new one?
The nut is removed and refitted every time the cartridge is cleaned or changed, so threads strip and the body cracks with repeated handling. Once it will not hold the cartridge down, the filter is bypassing.
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