I have a ~15 years old Whirlpool washing machine (Duet Steam with front load, model #W10251899C), which recently started getting F20 errors (insufficient water supply).

Even when the machine doesn't throw the error, water level in the machine during the washing cycle seems to be very low. Water barely covers the bottom of the drum (one inch above the lowest part of the drum, or even less). It's an HE model which is supposed to reduce water consumption, but I've owned other HE machines, and they all used more water

I have cleaned up the inlet screens, which seemed to have helped with the errors. But I was also wondering if I could increase the water level in the machine.

I tried to adjust the pressure sensor, but I couldn't find it. The closest thing to it that I did find was this valve/sensor on the water inlet block:

enter image description here

The third valve in the middle is connected with a rubber pipe to the white PVC air duct on the left hand side. The duct opens to the atmosphere. I thought that it was the pressure sensor, but I don't see how it can work, given that it's connected with the atmosphere.

I don't understand the function of this third valve/sensor.

I couldn't find the exact valve block online, but this one looks very similar to it (#WPW10247305):

enter image description here


(the first Google hit with a decent image, not affiliated).

What does the part marked as "mystery valve" on the picture do?

UPDATE, after some further investigation:

It seems to have the double function: this is indeed a steam valve and it is connected to the water pipeline by a tiny pipe inside the casing. I had to take the valve block off and look real closely to see it.

It seems to have the double function:

  1. Fill the drum through the diffuser pipe, bypassing the drawer. I couldn't activate this function in any of the normal cycles, but one of the cycles in the self-test has it.

  2. Let the steam out from the drum when the washing machine is full and the steam can't get through the water to the diffuser pipe.

  • Welcome to Home Improvement. If you'll take the tour, you'll note that this site works a bit differently than general discussion forums do. Your first two questions really make this too broad, as you're really (I think) asking about how to get your washer repaired. Your title question doesn't line up with that, either. The more theoretical "how does this work" and "what's this for" parts might be OK if you asked them as stand-alone questions, but they make this one too broad. Please edit your question to focus on the real, single thing you're interested in resolving, then ask others if you'd like.
    – FreeMan
    Feb 26, 2023 at 21:57
  • I copied and pasted your valuable update into this question. Once you have merged your accounts you will have author permissions for this question again.
    – P2000
    Mar 13, 2023 at 14:22

1 Answer 1


There are a few possibilities:

  1. The output of multiple valves lead to the detergent basket/drawer.

Depending on your model there is allowance for hot water, and for several additional drawer compartments.

The cold inlet is led to pre-wash, softener, bleach and main wash (1..4 valves), and the hot inlet valve (5th valve) mixes in hot water into the flow as needed for the temperature.

  1. It could also be a steam valve

It looks like they may have used a common 3-valve assembly and used the 3rd valve as a "Steam Valve" (SV). It would work as follows: with "Hot Valve" HV and "Cold Valve" CV closed, the controller can use SV to relieve steam/pressure from the drum housing back through the water hose.

I suspect the valve assembly interconnects the waterways and steam escapes via the blue water supply line, then the valve, and then green line.

The repair manual for your machine will detail the specific operation, the valve wiring, and the tubing.

enter image description here

enter image description here

Image: https://www.applianceblog.com, https://applianceassistant.com/Washer-Repair/Duet/Duet-Part-Testing.php

  • 1
    The third valve on my picture opens to the air duct. It's not connected with water. Feb 26, 2023 at 22:13
  • @WashingMachineUser how many compartments does your drawer have? That may not be an air duct but just a dummy hose for an unused function and unused valve in your particular model.
    – P2000
    Feb 26, 2023 at 22:26
  • three: bleach, softener and detergent. All the water goes in through a single rubber pipe marked with a blue highlight on the picture. Feb 26, 2023 at 22:31
  • 1
    ok, it could be the steam valve
    – P2000
    Feb 26, 2023 at 22:34
  • what does a steam valve do? Feb 26, 2023 at 22:35

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