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Your Shower Valve Has a Maximum, and Somebody Was Supposed to Set It

This is the most useful thing on this website, and it is about a part that is already in your wall.

At a glance

A shower valve carries an adjustable, lockable stop that caps how far the handle can move toward hot, and so caps the temperature it can discharge. ASSE states the installer must set it, and that the maximum safe temperature is mandated by local code. Frequently nobody has set it.

Source: ASSE International, Adjustment of Automatic Compensating Valves to Prevent Potential Scald Hazards.

ShowerValve is a referral service, not a contractor. We connect homeowners with independent contractors. Contractors are required to hold whatever credential their state or municipality demands, and valve work opening a wall is often a permitted alteration — ask to see the permit. We carry out no work, we sell no valves, we do not set prices, and we never charge homeowners anything — the contractors in our network pay us when we route them a call. The maximum water temperature is set by your local code, not by this website.

What a limit stop is

ASSE defines it as an adjustable and lockable means of limiting how far a device can be moved toward the hot position — which limits the maximum temperature the valve can discharge.

In plain terms: there is a physical stop inside the valve deciding how hot the shower is allowed to get. Turn the handle all the way and you reach the stop, not the water heater.

Source: ASSE International, Adjustment of Automatic Compensating Valves to Prevent Potential Scald Hazards.

A shower valve handle’s range of travel with its limit stopA semicircular arc runs from cold on the left to hot on the right. The handle can travel along the solid part of the arc as far as a marked stop set part way round. The remainder of the arc, toward full hot, is drawn as a broken line because a correctly set limit stop puts that travel out of reach.COLDHOTthe limit stopset by the installertravel a set stopputs out of reach
Turning the handle to its endpoint reaches the stop, not the water heater. Where that stop sits is a decision somebody made at installation — or did not.

Who was supposed to set it

The installer. ASSE is explicit that the limit stop must be set to the desired temperature at installation, and notes that manufacturers include detailed instructions with their products for doing it.

It is a step that can be skipped without anything looking wrong, because a valve with an unset stop works perfectly — it just works all the way up to whatever is arriving at it.

What the maximum is

ASSE states that the maximum safe water temperature, usually 120 degrees Fahrenheit, is mandated by the local code.

Read that carefully, because both halves matter. The usual figure is 120. The binding figure is whatever your local code says, and that is a question for your building department or the plumber doing the work, not for a website.

Why it is worth raising on a call

Because it changes what a visit is for. “My shower runs too hot” sounds like a valve replacement and is often a limit stop that was never set. Asking directly — has the limit stop on this valve been set, and to what — gets a different and usually shorter conversation.

It is also the right question when a shower has recently started feeling different after work elsewhere on the plumbing.

One direction only

This site will not tell you how to adjust a limit stop and will never tell anybody to raise one. The stop exists to cap a hazard; moving it up removes protection from everybody who uses that shower, including people who did not choose the setting.

If a shower is not hot enough, that is a conversation with a contractor about why, and the cause is frequently somewhere else entirely.

Ask whether it is the cartridge or the body.One is work through the trim, the other opens a wall, and the answer changes everything about the job. We will route you to somebody who covers your area, worked out from your ZIP code, and you are never charged. And if trouble elsewhere in the house needs attention, bring it up when you call.

Call (888) 752-7111
Call (888) 752-7111