I replaced the shower cartridge on my Delta Monitor Series 1300/1400 shower and turned the house water supply back On. Now I’ll check and adjust the shower valve hot water temperature and take apart the old cartridge to see why it leaked.

This project is continued from How to Install a Shower Valve Cartridge.

How to Adjust a Shower Valve Water Temperature

If you’ve never replaced a shower valve cartridge, the Delta Faucet shower cartridge model # RP19804 one page installation instructions can be a little confusing but it’s a simple process once you’ve got the basics.

Adjusting the shower water temperature is really about changing the Rotational Limit Stop (RSL) position which limits the shower handle “throw” (range of movement) to regulate the maximum flow of hot water. The RLS should be set so you won’t be scalded when the handle is turned to the full “hot” position.

Hot Water Heater Temperature Setting – Scalding vs Water Borne Bacteria

Because the water heater, sink, shower and bathtub faucets in my home do not have anti-scald valves I set my water heater thermostat to about 110 °F (or 43 °C) that can be tolerated for a several minutes without injury. This is lower than the recommended setting of 120 °F (or 49 °C) to minimize the chance of scalding. However lower temperatures can foster the growth of unhealthy bacteria in the water heater and pipes.

140 °F (60 °C) water heater temperature kills bacteria but scalds in 2 seconds (or less). To prevent scalding I would either have to replace all my faucets with anti-scald valves or devices (expensive and time consuming) or better install a single anti-scald device on the hot water heater such as Heatguard® Tank Booster.

The Unitrol thermostat on my natural gas water heater is set to slightly less than “warm”. Note that water heater thermostats are not very precise.

Gas Water Heater Temperature Control

Gas Water Heater Temperature Control

Adjust the Shower Valve Temperature

To adjust the shower valve temperature:

  1. Recall the shower valve is in the Off position (see the previous project).
  2. Be careful to point the shower head in a safe direction so you don’t get drenched or scalded.
  3. Temporarily press the shower handle on the brass stem of the shower valve cartridge.
    Hold the shower handle so it doesn’t fall off.
  4. Slowly turn the handle to the full Hot position.
  5. Wait until the shower water temperature stabilizes.
  6. Is the water too hot, just right or not hot enough?
    I use my personal judgement for what I consider comfortable and safe. A thermometer would be more precise.

If you’re OK with the full Hot water temperature skip to Reattach the Shower Handle.

If the shower needs to be hotter or colder, adjust the temperature by the following steps:

  1. Push the trim sleeve inward a bit to expose the Rotational Limit Stop (RLS) to grasp it with your fingers – see the following photo.
  2. Pull the gray disc out from the brass cartridge stem.
    The disc holds the RLS in the cartridge cap. The disc just slides on & off the stem.
  3. Note the factory default index marked on the shower cartridge cap (see the next photo).
  4. Wiggle the RLS out of the cap until you can rotate it.
  5. Rotate the RLS counter-clockwise for hotter and clockwise for cooler water temperature.
    – The hotter/colder direction is marked on the RLS.
    – Adjust the RLS one or two ticks at a time.
  6. Press the RLS back into the cartridge cap so the geared teeth fit together.
  7. Turn the shower On to the full Hot position and recheck the water temperature.
  8. Readjust the RLS position until you’re satisfied with the temperature.

My shower needed to be much hotter so I turned the RLS counter clockwise as indicated in the photo to align the index pointer with the hottest tick mark on the shower cartridge cap:

Adjust the Shower Valve Cartridge Temperature Setting

Adjust the Shower Valve Cartridge Temperature Setting

The Rotational Stop Limit (RLS) sets how far the shower handle can be moved toward the Hot side. This is my shower Before (not warm enough) and After (hotter) adjusting the RLS:

Shower Valve Temperature Adjustment

Shower Valve Temperature Adjustment

When you’re finished adjusting the shower temperature, press the gray disc over the brass stem against the RLS then pull the trim sleeve out to cover the RLS:

Shower Valve Sleeve Adjustment

Shower Valve Sleeve Adjustment

Reattach the Shower Handle

Press the shower handle onto the brass cartridge stem and reinstall the set screw with the Allen wrench. I cleaned my set with a wire brush to remove the 12 years of soap and mineral deposits:

Shower Handle Set Screw

Shower Handle Set Screw

If the shower handle squeaks when turned it may be rubbing against the trim sleeve. Push the trim sleeve inward slightly so it doesn’t rub.

The leaky shower cartridge replacement job is now complete!

What Caused the Shower Valve Cartridge Leak?

I was curious what caused my shower cartridge to leak after ~12 years of service so I dissembled it. This is the older Delta Faucet shower cartridge model # RP19804 made before March 2006 that’s identified by the off-white lower housing:

Delta Shower Valve Cartridge RP19804 - Made before March 2006

Delta Shower Valve Cartridge RP19804 – Made before March 2006

Water flows from the shower valve body through the lower housing. The hot & cold water is mixed in the cartridge cap and flows out the base to the outlet in back of the shower valve body:

Delta Monitor Series 1300 1400 shower valve cartridge

Delta Monitor Series 1300 1400 shower valve cartridge

Rubber flapper type backflow prevention valves are necessary for the automatic pressure balance valve inside the lower housing to operate:

Shower Valve Cartridge Backflow Prevention Valves

Shower Valve Cartridge Backflow Prevention Valves

How a Shower Cartridge Valve Operates

Moving the shower handle turns the cartridge brass spindle and mixing plate:

  • Left photo: The mixing plate starts at the full Off position.
    Note the gray rings from the rubber seats on the mixing plate blocking the water flow.
  • Middle: Hot water is beginning to flow and mix the cold water.
  • Right: Full Hot position with maximum hot water flow.
Shower Valve Cartridge Operation - Hot and Cold Water Mix

Shower Valve Cartridge Operation – Hot and Cold Water Mix

The rubber seats are pressed against the mixing plate by the springs. I believe my shower valve leaked because the springs relaxed allowing water to leak past the seats when the shower valve was Off. The whitish substance on the seats are calcium mineral deposits which may have also interfered with a water tight seal:

Shower Valve Cartridge Seats and Springs

Shower Valve Cartridge Seats and Springs

Shower cartridge seats and springs repair kits may be available for several dollars. But for the trouble of removing the cartridge why not just replace the entire unit?

If you can’t readily obtain a replacement cartridge you might try stretching the seat springs to temporarily stop the leak.

Here’s the partially disassembled shower valve cartridge showing the water pressure balance valve. The lower housing just press fits together:

Delta Shower Cartridge RP19804 Disassembly - Lower Housing

Delta Shower Cartridge RP19804 Disassembly – Lower Housing

The fully disassembled Delta shower valve cartridge. The piston moves back and forth inside the pressure balance spool to automatically balance the hot and cold water pressure. If your cartridge happened to leak around the shower handle then a cap O-ring may have failed.

Delta Shower Cartridge RP19804 Disassembly with Pressure Balance Valve

Delta Shower Cartridge RP19804 Disassembly with Pressure Balance Valve

Except for the rubber seats all the O-rings on my shower cartridge were flexible and appeared to be in good condition.

You can find replacement parts, diagrams and instructions at Delta’s Customer Support site. Once you’ve identified the part # it’s often available at Amazon.com for a much better price.

Hope this helps,

Bob Jackson

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