Shull Piano Inc

610 Amigos Dr., Redlands, CA  92373

909 796-4226




Bill Shull, RPT     Catherine Lee, Manager

Serving the greater Inland Empire, Redlands, Loma Linda, Highland, San Bernardino, Riverside, Corona,  Norco, Eastvale, Ontario, Rancho Cucamonga, Temecula,others

Staying at home?  No better time to buy a piano from Shull Piano and create beautiful music!

    LA SIERRA UNIVERSITY Department of Music

    1.  Humidity System Service Procedures

    Purpose of Humidity Control

    Water Maintenance Procedures

    List of Pianos With Humidity Control

    2. Piano Service Report


    The purpose of humidity control:

    Humidity control prevents extreme tuning instability, ensuring a more durable piano tuning, up to 75% improvement in pitch stability.   It also prevents cracks in soundboards and damage to soundboard structure.

    Keep systems plugged in

    Humidity systems must always remain plugged into the wall outlet;  some wall outlets are exposed and are frequently found unplugged, please check regularly and put plugs back into the wall as needed.

    Reduce room air flow: 

    The system will not work effectively if there is air flow past the piano.  The most likely situation is if a window is left open during Santa Ana winds, or any wind event.  Please keep windows closed in windy weather, or just open an inch when fresh air is needed.

    How system works:

    HUMIDISTAT:  All systems have a humidity control device (“humidistat”) plugged into the wall which controls whatever is plugged into it, a humidifier or dehumidifier. 

    DEHUMIDIFIER:  All systems have a de-humidifier which keeps the moisture below 47%.   The dehumidifier also regulates the swings of the humidifier, if present.  The dehumidifier works to prevent the high humidity common in both the “onshore flow” or ocean-influenced climate which keeps us cooler in southern California;  the monsoonal summer moisture (the “gulf of Mexico” influence), and the occasional rain storms of the winter. 

    The dehumidifier consists of long bars attached to the piano which heat the surrounding air, reducing moisture content.  Some systems have ONLY a dehumidifier without a humidifier, and these systems should remain plugged in at all times;  trust the humidistat

    HUMIDIFIER:   Most systems also have a humidifier, which is especially important during Santa Ana wind conditions which sporadically occur between the fall and spring in southern California.  Similar conditions sometimes occur during the summer;  these are caused by “offshore high pressure systems.”   The air mass changes directions, and except for monsoonal conditions, usually is dry and creates compressional heating, further causing extreme dryness.  During the cold winter weather the use of heating takes out any moisture still left in the air!  

    The humidifier consists of a bucket of water (or buckets, in longer grands) with a heater bar on top and absorbtive pads draped over the bars into the water.  Pads draw water up over the bar, which heat the water and actively evaporate moisture into the air below the soundboard.


    All systems have some kind of light or light panel for service maintenance. 

    1.  One piano (a black Steinway 6’ grand) has only an amber light which flashes when water needs refilling.

    2.  Most pianos have a light panel with three lights. 

    The green light should stay on all the time;  it indicates the system is plugged in.

    The yellow light flashes when water is low.  THIS IS YOUR MOST IMPORTANT LIGHT for replacing water, re-fill immediately with the premeasured pitcher and you will prevent the bucket from becoming dry.

    The red light should never flash, if the system has even the lowest level of maintenance.  It is supposed to show when the humidifier has dried out, but this light is unreliable.  DO NOT WAIT FOR THE RED LIGHT TO COME ON!!!   On some systems, the light does not work, and it shouldn’t be used as an indicator for refilling, anyway!    Repeating:   The red light should never be allowed to flash, always use the yellow flashing light as your water-refill indicator.

    The “smart bracket:”  On newer systems the signal for the red light also turns off the humidifier, when working properly.  This is a feedback from the top of the pads, if they stop wicking water or the bucket becomes dry.  Most systems at LSU have this feature (except the Steinway “O” 6’ grand), but its best not to rely on this feature, as it may not function any better than the unreliable red light.  Always refill as soon as the yellow low water light flashes.

    Water formula:  Use only distilled or purified water without replacement minerals (no “drinking water”).  Each re-fill should include 1/2 to 1 capful of DamppChaser Treatment Solution.

    Pad Replacement:  The pads should never become hard from mineral deposits.  Eventually even the controlled electrolyte added with the treatment solution will build up and harden the pads, requiring replacement.  The piano technician will check these pads and replace as necessary; it is possible to displace the plastic baffle, or the tank hangers, while checking pads, so care must be exercised while checking pads.

    Frequency of refilling:  The water must be re-filled every 5 to 14 days, depending on weather conditions.  Dry weather requires frequent filling and wet weather, less frequent.  If you are assigned to maintenance, please check the pianos frequently to be sure they are operating (light is on, system plugged into wall), and check for the low water light every day or two if more than 5 days has passed.

    Normal Refill Procedure:

    First time user: It is a good idea to 1. Read this entire page thoroughly until you fully understand it.  2.  Lay under the grand piano with a complete system so that you might best understand the layout and components;  especially note the refill tube and how it is laid out;   see how the parts are installed when fastened properly and note that many parts are held by plastic clips and can be forced free.  Use this knowledge in normal maintenance, sometimes parts are displaced accidently or by mal-intent, and you can mitigate this or report it.

    1. Refill water as soon as the yellow light begins to flash (low water light)

    a.  Fill the pitcher to the pre-measured amount, and add treatment solution (1/2 capful, 1 capful for the Yamaha C5’s in Dr. Smith’s studio)

    b.  Find the end of the plastic tube under the piano (it should be kept in a plastic clip under the piano). 

    c.  Connect the tube:  Push the tube firmly onto the pitcher spout so that it will not fall off.

     d.  Empty the pitcher into the humidifier:  Raise the pitcher high enough ((almost to the top of the piano, if possible) and tip the pitcher so that  the water will empty into the humidifier bucket.  Do not pull the tube tight, keep a relaxed tension to avoid pulling it through beneath).

    f.  Empty the tube and disconnect:  Do not disconnect yet;  first lower the pitcher so that the tube can empty its remaining contents into the pitcher.  tap the tube with your hand to shake droplets of water free.  Only after the tube is empty can you disconnect the pitcher from the tube.  Do this with a hand on each part - tube and pitcher spout - so that the tube is not pulled out of its fasteners.

    g.  Re-install tube on its retention hook(s).

    h.  Check to be sure window in room is not wide open, and close or leave open only crack.

    2. Other responsibilities:

    a.  Maintain a good supply of purified or distilled water.  Use department-supplied water distilling resources to keep a sufficient supply of purified water.  DO NOT allow the service of the system to be limited by a lack of water!

    b.  Check supply of Humidity Treatment Solution and report when low.  Piano technician can supply new bottles, and these can also be ordered at the DamppChaser website

    c.  Note other piano service needs and report when found (see instructions below)

    Report all concerns to both the music department and to the department piano technican, Bill Shull, RPT, M.Mus.  by text to 909 796-4226 and/or email




HMA 133 Steinway B Grand (older) (humidifier with two buckets, refill with 2 pitchers)

HMA 133 Steinway B Grand (newer)  (humidifier with two buckets, refill with 2 pitchers)

HMA 205 - Yamaha C5 6’6” Grand (door)  (humidifier system)

HMA 205 - Yamaha C5 6’6” Grand (window)  (humidifier system)

HMA 214 - Baldwin L 6’3” Grand (humidifier system)

HMA 232 - Steinway “O” 6’ Grand (humidifier system, no “smart bracket”)


HMA 117 - Yamaha C3, Violin Faculty  (dehumidifier only)

HMA 118 Yamaha C2 (dehumidifier only)

HMA 120 Yamaha C3 (dehumidifier only)

HMA 220 Yamaha C1 (dehumidifier only)



Please report service needs as follows:

1.  HMA Room Number

2.  Piano Description (Make, Grand/Vertical)

3.  Description of Problem.  Include affected notes, using octave numbering system beginning with lowest C as the first octave (C1).

4.  Your Name and major 

Your report will be included in a priority service list for the piano technician service days.



[Home] [SERVICE & RESTORATION] [Regular Maintenance] [Actions] [Rebuilding] [Pianos We've Rebuilt] [Restorative Conservation] [Refinishing] [Benches] [String Covers] [DamppChaser Humidity Control Systems] [La Sierra University] [RETAIL SALES] [RENTAL] [HUMIDITY CONTROL] [PIANO ACCESSORIES] [TESTIMONIALS] [ABOUT BILL SHULL] [About PTG] [Programs and Classes] [How to Buy a Piano] [Directions to Shull Piano]