Kohler GP876851 mixer cap and pressure balancing unit kit
GP876851 is two Kohler parts in one box: the GP77759 mixer cap and the GP800820 pressure balancing unit that sits behind it. Kohler lists the pair for K-304, K-305 and K-11748 valves. A round stem, a black plastic cap and two cap screws point to this kit.
Schematic, not to scale. It shows only the features named on this page. No bench photo of this part yet.
The current kit. Kohler's service parts brochure says it consists of GP800820 and GP77759.
GP76851
Kohler
Older number for the mixer cap and pressure balancing unit kit. Kohler's genuine-part copy, as carried by parts sellers, says GP876851 replaces it.
GP77759
Kohler
The mixer cap alone. Kohler calls it the stem cap for most 1/2 in. pressure-balancing valves. No pressure balancing unit in the box.
GP800820
Kohler
The pressure balancing unit alone, no cap. Kohler's brochure says it replaces GP500520.
GP500520
Kohler
The earlier pressure balancing unit alone. Kohler's 2011 catalog pairs it with the GP77759 cap on these valves.
Where it goes
Kohler's 2011 service parts catalog lists the GP77759 cap and the GP500520 cartridge for the K-304 1/2 in. Rite-Temp pressure-balancing valve, and the same pair for the K-11748 and K-305 valves with diverter.
Kohler's valve identification tool names Mixer Cap and PBU as the common service parts for the K-304, the K-305 and the K-11748.
Kohler's 2011 catalog shows these valves under trim styles from 1998 on, including Bancroft, Devonshire, Fairfax, Forte, Memoirs, Purist, Revival and Stillness, and lists the same GP77759 cap and GP500520 cartridge for Flair II, Paladar, Taboret and Triton trims from before 1998.
Kohler Assist says an early K-304 with a brass cap and a three-ribbed stem takes the GP876851 combination when the pressure balancing unit is replaced.
Confirm it is your part
Pull the trim. If an adaptor sits on the end of the stem, slide it off. The stem underneath is round and splined. A square stem is a Coralais valve and takes different parts.
The cap is black plastic. Kohler's identification tool sends a round stem with a brass cap down a separate branch: an early K-304.
Count the screws that hold the cap to the valve body. Two: K-304, K-305 or K-11748, and this kit. Four: K-8304, a different cartridge. Six: K-306 or K-2971 Hi-Flow, a different cap and unit.
Look for a diverter button. None is a K-304. A button with no threads on its end is a K-305. A threaded button is a K-11748. Kohler lists the same cap and unit for all three.
A metal collar sits over the front of the cap, under the two screws. Kohler notes it is sometimes not present. Behind the cap, the pressure balancing unit is a separate piece inside the brass body.
Kohler's service kit sheet draws the round-stem cap as Style B: a tab on the cap and a collar over it. Its Style A cap, marked UP with an adapter behind it, is drawn with a square stem.
Count the splines on the stem. Catalogs list a 19-point broach.
Look-alikes
Kohler GP800820 or GP500520, the pressure balancing unit alone
Why it gets confusedIt sits behind this cap in the same valves, and sellers call both pieces the Rite-Temp cartridge.
How to tellNo stem, no flange, no screws. It is only the unit left in the brass body after the cap comes off. If the cap is the failed piece, the unit alone does not replace it.
Kohler GP77759, the mixer cap alone
Why it gets confusedIt is the same cap as the one in this kit, so it looks identical from the front.
How to tellSame round splined stem, same valves. The difference is in the box: GP77759 is the cap only. GP876851 is that cap plus the GP800820 unit.
Kohler GP77886, mixer cap with square brass stem
Why it gets confusedAnother black mixer cap over the same style of pressure balancing unit.
How to tellThe stem is square, not round. Kohler lists GP77886 for older Coralais shower valve trim, and its identification tool calls a square brass stem a K-15700 or K-15701 valve. A square plastic stem is GP71969.
Kohler GP800881, cartridge for the K-8304
Why it gets confusedAlso sold as a Rite-Temp pressure-balancing cartridge, under a number that reads almost the same.
How to tellKohler calls it a one-piece pressure-balancing cartridge for the K-8304 valve. The K-8304 cap is held by four screws. This kit's cap is held by two.
Kohler 85500 cap and GP1144925 cartridge
Why it gets confusedSame layout, a cap over a pressure balancing unit, on Kohler's high-flow valve.
How to tellKohler lists them for the 3/4 in. high-flow pressure-balancing valve, K-306 and K-2971. Six screws hold that cap, not two.
Cross-reference numbers
Numbers other makers and sellers list against this part. The notes say how far each one goes.
Maker
Number
Note
Everbilt
71869
sold as replacement for GP76851; contents not itemized
Everbilt
37973
cap only, GP77759
Everbilt
49868
pressure balancing unit only
Kissler
46-0080
pressure balancing unit only; one retailer page
Not printed on this page
Where the sources disagree, the figure is left off until it is settled.
Overall length of the cap and stem. Catalogs and retailer pages disagree, so no figure is printed.
Body diameter and the size of the pressure balancing unit. Sources give different figures and do not say what each one measures.
Sterling fitment and Sterling part numbers. Only retailer pages make the link, and only for the pressure balancing unit. No Kohler or Sterling document was found.
The year the K-305 was discontinued. Two Kohler documents give two different dates.
Older Kohler service numbers quoted by one retailer for the pressure balancing unit. They were not found in a Kohler document.
Field notes
Kohler changed the mixer cap design in 2005. The earlier cap had a removable section, and if it separated the boots and springs could fall out. Kohler does not sell the boots and springs as parts. The cap is replaced.
FourHome replacement
The FourHome replacement for Kohler GP876851 ships as a kit: the mixer cap, the pressure balancing unit, four O-rings and two cap screws.
FourHome replacement
Replacement for Kohler GP876851 Mixer Cap and Pressure Balance Kit
Catalogs disagree now and then, and makers revise parts without changing the number. Compare the old part before buying. Identify by measurement lists every indexed part near a given length and spline count.
