How to Replace a Mixet MS-5AT-C Single-Handle Tub and Shower Cartridge

If you own a house built between the late 1960s and the mid-1990s and the single-handle tub and shower in the hall bath has started dripping, weeping behind the trim plate, or losing its temperature setting, there is a strong chance you are looking at a Mixet valve. The brand is no longer sold under its own name, but the valves Mixet installed by the millions during the boom years of post-war American homebuilding are still mounted inside countless walls today. The fix is almost always the same single replacement part: an MS-5AT-C cartridge.

This guide covers the part you need, the brand history behind it, and how to install it without opening drywall or calling a plumber. By the end you will know whether you have a pre-1968 or post-1968 Mixet, why that distinction matters, and what to order from a phone in under three minutes.

A Short History of Mixet

Mixet was an American single-handle tub and shower valve manufacturer that rose to prominence in the years following Al Moen's commercialization of the single-handle mixing faucet in 1947. Where Moen focused primarily on kitchen and lavatory faucets, Mixet built its business on the shower side: simple, durable, single-handle compression-style tub and shower valves that builders could install fast and homeowners could understand at a glance. One handle, one motion. Push or pull for off and on. Rotate for temperature.

By the late 1960s Mixet was one of the most-specified single-handle shower valves in mid-priced residential construction. The design was a non-pressure-balance valve, meaning hot and cold flow were mixed mechanically by the position of a single moving stem rather than by a thermostatic spool. It was less sophisticated than the pressure-balance valves that became code-mandated decades later, but it was reliable, cheap to make, and trivial to service. A homeowner with a wrench and a fresh cartridge could keep one running indefinitely.

In 1968 Mixet redesigned the internals of its single-handle valve. The body geometry changed, the cartridge got shorter, and the stem profile changed with it. From that point forward the brand effectively shipped two valve families: the older long-stem pre-1968 design, served by the MS-3T cartridge, and the newer short-stem post-1968 design, served by the MS-5AT-C. Both families remained in production for decades.

Mixet eventually wound the brand down, and the rights to manufacture replacement parts were licensed to Alsons and its sister company BrassCraft. Alsons had been acquired by Masco Corporation in 1987, and BrassCraft, founded in 1946, was already a Masco subsidiary after its 1983 acquisition. The Mixet name disappeared from new valve installations but the parts kept flowing through the BrassCraft and Alsons distribution channels under cross-reference numbers like SLD1350 and MXT07. Danco, Prime-Line, and other aftermarket suppliers followed with their own equivalents.

Today, the single-handle Mixet valve is a mid-century survivor: still in the wall, still working, still drip-prone every five to ten years, and still serviceable with a $20 part you can have on your doorstep tomorrow.

Do You Actually Have a Mixet?

The fastest way to identify a Mixet single-handle tub and shower valve from the outside is the trim. A classic Mixet has a single round or oval handle mounted on a trim plate (called an escutcheon) with a small temperature indicator window underneath. Many used a clear acrylic knob marked OFF, HOT, and TEMP. The trim feels lightweight compared to a modern Moen or Delta.

If the handle and trim are not original, the next step is to open it up. Shut the water off at the house main, pop the handle off, and pull the trim. Behind the trim plate you will see a chrome cylindrical retaining nut threaded into the brass valve body. That nut is the Mixet signature. Unscrew it and a small brass stem with a white polymer body slides out the front of the valve. If what you pull looks like the cartridge in the diagram below, you have a Mixet.

Figure 1 · Before and AfterWorn Mixet cartridges drip from the spout, weep behind the trim, and lose temperature consistency. A new MS-5AT-C restores like-new operation in 15 minutes without opening the wall.

Pre-1968 vs Post-1968: Which Cartridge Do You Need?

This is the only branching decision in the entire repair. Mixet sold two single-handle valve generations. They look almost identical from the outside but the internals are different lengths.

The simplest way to tell which version you own is to pull the old cartridge and measure it. A 6-1/8 inch overall length is the older MS-3T. A 4-1/2 inch overall length with a polished chrome sleeve around the body is the newer MS-5AT-C. There is no in-between. The rest of this guide covers the MS-5AT-C, which is the cartridge installed in the overwhelming majority of Mixet valves still being serviced.

The 1968 redesign also dropped the pressure-balance question for good. Both generations of single-handle Mixet are non-pressure-balance valves. If somebody opens a toilet line while you are showering, the cold flow drops and the temperature spikes. This is normal Mixet behavior, not a sign of a bad cartridge. A new MS-5AT-C will not fix the scalding-when-toilet-flushes problem because the valve itself was never designed for it. If that bothers you, the only true fix is to swap the entire valve body for a modern pressure-balance valve, which means opening the wall.

What a Failing MS-5AT-C Looks and Feels Like

The MS-5AT-C is a wear part. It is built around a brass stem turning inside a polymer carrier with rubber and Teflon seals between them. The seals harden, mineral deposits build up, and the carrier loses its precision fit. The failure modes are predictable:

• Constant drip from the tub spout or showerhead even with the handle fully off
• Water weeping out from behind the trim plate during a shower
• Temperature creep, where the set point drifts hotter or colder over the course of a shower
• Handle that turns past its travel stop without shutting the water off
• Handle that becomes stiff, gritty, or hard to turn smoothly
• Loss of full hot or full cold (the cartridge can no longer reach the extreme positions)

Any two of these is enough to justify a replacement. Cartridges are consumables. Five to ten years is a normal service life, less in hard water markets.

The MS-5AT-C, Anatomically

The FourHome MS-5AT-C replacement is built around a precision-machined brass stem mounting base, a reinforced internal polymer body designed for long-term hot water exposure, and a chrome-plated outer sleeve for corrosion resistance behind the trim. Overall length is 4-1/2 inches, body diameter is approximately 1 inch, and the bottom is cut with a 1/4 inch deep notch that drops into a matching tab inside the Mixet valve body. That notch is what orients the cartridge to hot and cold. Get the notch wrong on install and your hot and cold will be reversed.

Figure 2 · MS-5AT-C Dimensions4-1/2 inch overall length. 0.75 inch top stem and bottom outer diameter. Replaces Mixet MS-5AT-C, Danco 88200, BrassCraft SLD1350, and Prime-Line MP58045.

The cartridge ships with three components needed for a complete install:

• The cartridge itself, with the brass stem and polymer body preassembled
• The chrome-plated outer sleeve that goes between the cartridge body and the trim plate
• The threaded retainer nut that locks the cartridge into the valve body

You do not need to reuse worn hardware from the old install. Brass washers between the cartridge and the retainer nut are also included, as is a plastic spacer washer.

OEM Cross-References

The MS-5AT-C is one of the most-cross-referenced single-handle cartridges in the aftermarket. If your old part is labeled with any of the numbers below, the FourHome MS-5AT-C is a drop-in replacement.

Same dimensional footprint, same seating profile, same 1/4 inch orientation notch. If your valve takes any of those references, it takes the MS-5AT-C.

Valve Layout: Where the Cartridge Lives

The MS-5AT-C sits horizontally in the wall, behind the trim plate, with the brass stem facing out toward the room and the brass tail with the chrome o-ring seal facing back into the valve body. Cold water enters from one side, hot water from the other, and mixed water exits either up to the showerhead or down to the tub spout depending on whether the diverter at the tub spout is engaged.

The 15-Minute Install

The whole job is five steps. If you have a wrench and a Phillips screwdriver, you can do it. Total time on a first attempt is about 15 to 20 minutes including cleanup. Subsequent units in the same building drop to under 10 minutes each, which is why property managers often stock these in cases.

Figure 4 · Install SummaryFive steps. About 15 minutes for a first attempt, under 10 minutes for subsequent units in the same property.

Common Mistakes to Avoid

What Else You May Want to Replace While the Wall Is Open

If you are going to the trouble of pulling the handle and trim, it is worth thinking about the other consumables on the same fixture. A few things to consider:

The handle and index button

Mid-century Mixet handles were often clear acrylic, and acrylic yellows, cracks, and chalks over decades of hot water and bath products. Generic replacement handles in the Mixet pattern are inexpensive and snap onto the same brass stem broach. Refreshing the handle at the same time as the cartridge makes the whole fixture look new from the outside for the price of one ten-minute swap.

The tub spout and its internal diverter

On a single-handle Mixet, the diverter that switches water from the tub spout up to the showerhead lives inside the tub spout itself, not in the wall valve. If your shower is not pressurizing fully when you pull the diverter, the failure is almost always inside the spout, not the cartridge. Replacement tub spouts with built-in diverters cost less than a cartridge and screw on in two minutes.

The showerhead

If the cartridge has been struggling for years, the showerhead has likely been collecting mineral scale at the same time. A vinegar soak overnight or a fresh head can recover lost pressure independent of the cartridge swap. See our low water pressure shower guide for the full diagnostic.

The lavatory and kitchen faucets

If your house is old enough to still have a Mixet shower valve, the lavatory faucets in the same generation are often two-handle Pfister or Sayco stem faucets that wear out on the same schedule. Pulling the bibb seats and stems on those at the same time turns a one-shower project into a whole-bathroom refresh. The Sayco 308 stem replacement guide covers the most common companion repair.

Specs at a Glance

Figure 5 · CertificationsFourHome plumbing components ship certified to ASME A112.18.2-20, NSF/ANSI/CAN 61, and NSF/ANSI/CAN 372 lead-free standards.

Where the Mixet Lives Today

The Mixet single-handle valve found its way into a remarkably wide range of buildings during its long production run. The same MS-5AT-C cartridge is at home in suburban tract housing from the 1970s, multifamily walk-ups built through the 1980s, mid-century motel rooms still in operation, school dormitories, mobile homes from the manufactured housing boom, and the small hotels and motor lodges that punctuated American interstate routes during the highway era. Property managers running portfolios of older multifamily units quickly recognize the Mixet trim and order MS-5AT-C cartridges by the case.

Figure 6 · Where Mixet Lives TodayHospitality, institutional, multifamily, and residential applications. The MS-5AT-C is the universal post-1968 Mixet replacement.

Order the Right Part

Why FourHome: Our Mixet MS-5AT-C replacement is manufactured to the original post-1968 Mixet dimensional specification. Same brass alloys, same body diameter, same 1/4 inch orientation notch, same washer stack as the OEM cartridge that originally shipped in the wall. The chrome-plated sleeve and retainer nut are included so you do not have to reuse hardware that has been baked in hot water for thirty years. Ships from Amazon FBA. Volume pricing available for property managers and multifamily portfolios through FourHome Pro.

Not sure whether you have a Mixet or a different brand entirely? Run the Stem and Cartridge Finder for a three-click visual match against every cartridge in the FourHome catalog. If you do have a Mixet but you are unsure whether it is pre-1968 or post-1968, the safest move is to pull the old cartridge first and measure it before ordering.