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I have both studied the system, and used it on my own pianos for more than ten years in three different states, and must share my opposing view to your findings. Many manufacturers feel that the system is effective:
http://www.dampp-chaser.com/mfg_recs_n.html

Again, the water dispersed is typically a gallon every ten days, not a quart. I typically install 100 watts of heater bars in a grand, not the 40 or so you mention. I also install a grand undercover most of the time to cover the entire underside of the soundboard, which holds the moisture in and blocks drafts (yes, it breathes).

Installers select the right size and number of system components for the given piano and environment. For example, for a 6' piano in a two-story-tall living room with south-facing windows that got very hot, I installed a system with dual humidifier tanks and an undercover. For an upright in a very damp church (70% RH -- water drops had condensed onto the tuning pins when I first saw the piano), I added an additional 25W heater bar on top. A year later, humidity variation was within spec, and both pianos were much more stable.

I encourage you to examine an actual installed system in someone's home, or even just search the forum, where others have posted actual graphs of measured humidity over time.

My intent is not to offend, either; I'm sharing my real world experience. I sell and install the system (disclaimer) because it works. I'm not a shill for the product, though. Not every piano needs one; when I lived in coastal California, I didn't have a system in my piano. Whole house systems can work great; I agree with you.

But I have abundant experience that the system does stand up well to both extreme dryness and moisture (that's why they renamed it from "Dampp-Chaser"). I think you'll find many people on this list who have the system and also find that it works well. One easy way for any piano owner to tell if the system works is to compare how far their piano drifts off pitch before and after the system is installed.

--Cy--

The system does continuously switch from wet to dry; there are no dead bands. The reason is to circulate air without using any moving parts.

While conditions may change momentarily, the absorption rate of wood is much slower. The system keeps the changing conditions within a much narrower range overall than in most homes, and it's those extreme variations that are damaging.

I started a tuning here one summer with measured RH at 30%. Half an hour later, I noticed it was up to 60%. The owner mentioned that she had helpfully turned on the swamp cooler (evaporative) for my comfort! A PLSS will hold the variations to half that range. The temperature variations are small. I can confirm that there is no long-term damage from such small cycles; preventing the big swings is the point of the system.

A whole-house system can work even better than a PLSS, as there is more moisture in the entire room. Temperature ranges would be a lot less, unless you have an offset thermostat to turn down the heat at night, or if the room is not always heated (churches and other institutions can be very harsh environments).

--Cy--

In general what is good for the piano is also good for the people (your wife and daughters will love it, as women are more sensitive to dryness), the house (nail popping will be a thing of the past), and you plants. And only whole-house humidifiers and large capacity consoles can humidify the house. The biggest advantage of the whole-house type is that they use a constant running stream of water so that bacterial or mold can not grow (they need a drain). All other types that do not use a running stream of water needs cleaning disinfecting every other week, or they become a health hazard.

And again, for Maryland or similar regions, you need an output capacity of 12 gallons per day per floor. That's why most console types range from 10 g to 15 g in capacity. So if a particular system uses 1 gallon every 10 days, that is 0.1 gallon per day, which is 1/120 of what's required. And if you do not clean/disinfect it every other week, you put your health at risk (wonder if owners of this type humidifiers suffer from mold related illness, such as neurological disorders? )

Cy has already done an outstanding job articulating the benefits of the system, but there are a few things you've said James that warrant clarification:

If you have a 'steam' type humidifier then yes what you said is correct. You can set the fan to 'on' and the unit will produce steam, even without the furnace on. If however,it is the type that sprays a mist, you cannot do this, as the water will simply pool up in your duct work!

Even not so modern pianos were finished with shellac, which is has excellent ratings against water-vapor exchange. (much better for instance than nitrocellulose lacquer)

Your comment though that it isn't harmful to drop the RH in a piano for 'even a few months' is irresponsible. The fact that pianos go dry 'for a few months' and then go back and forth is exactly what causes LONG-TERM damage.

It is correct that a piano can often go back and forth between humid and dry without showing obvious cracks----for a time. That doesn't mean damage isn't being done to the piano. As Cy often points out, humidity control can't repair damage--it can only prevent it!

Scare tactics and endorsements - Can you show me something new and constructive in marketing the DC systems? Arguably concert halls have the best sounding pianos, but I have never seen any concert pianos have the DC system installed. Most of them sound just wonderful to me. Maybe I have not been to enough piano concerts, so I need to do it more often.

But thank you for pointing out the "mist spray" type whole-house humidifiers that can not run when the heat is not on - They have largely disappeared from the market, as they are truly terrible type, as they spew out white dust big time as well as cause numerous other problems.

As I understand it, the concept of the DC is to maintain a constant humidity in the air immediately below the soundboard. The air above the soundboard is however presumably at the ambient room humidity, which might be (let us say) significantly lower. But wood absorbs moisture from air relatively slowly. If in comparison moisture diffuses relatively fast through the wood (can someone confirm whether this is true?), the effect will be that the soundboard has a fairly uniform moisture content, at an equilibrium between the damper air below and the drier air above. If this is the case, differential expansion would not be a problem.

There is an analogy between moisture transfer and heat transfer. So the situation is analogous to a metal plate with warm air on one side and cold air on the other. The temperature of the metal will be somewhere in the middle - but it will be uniform throughout the metal.

My concern about the D-C is rather different. What happens to the other parts of the piano, that are not near to the D-C unit - the action, the wrest plank (pinblock) and the wooden case? It is not at all clear to me that the D-C is going to keep these parts at a constant moisture content, because it is too far away, and the influence of the ambient room humidity will be too great.

To give an example. The veneer on my own piano has suffered from excessive central heating in the past, before I installed a humidifier. One result was the developing of a slight crazing / waviness of the veneer surface. The room humidifier has stopped this getting worse. But I can’t see that a D-C would have been effective in preventing it.

Humidity spread is very rapid. We all have the experience of cooking onion. If you do not turn on a range hood vented to outside, the smell will spread to other parts of the house almost immediately. Try to use any cloth material to contain or otherwise “seal” the smell – it is futile. Humidity spreads in the same way and at the same speed.

Now if you have a system installed under a piano, that outputs only 1/120 of the water required to adequately humidify a single floor, it will not raise the RH even by 1% immediately below the soundboard, regardless how well the underside of the piano is “sealed”. I know this, because I measured just such a piano at my former church over an entire winter, a number of years ago.

Despite my intention otherwise, I probably have already offended many members of this board. So this is my last posting on this topic.

In the paragraph you quoted me, I was referring to humidity control in general, not simply any piano without a D-C system. I work full time in a piano restoration shop. My job is repairing damage caused by swings in humidity. (maybe I should reconsider my endorsement of the system!! ) This isn't a matter of marketing. It is a matter of presenting information that is correct, vs information that is incorrect.

No one that I know of has stated that the purpose of a Dampp-Chaser system is to "make your piano sound like a 9' Grand in a concert hall that has been serviced by a high-level technician immediately prior to being played by a world class musician!" The purpose of the system is to stabilize the moisture content of the wood sufficient enough to prevent damage caused by humidity swings. In doing so, the overall pitch of the piano is stabilized, which can have the result of the customer being happier as the tuning doesn't drift so far out between service calls.

While there aren't many new units of type being sold, I still run into more people who have that type, than who have the steam type. (yes we ask)
In fact, we had one of the mist types for a couple years ourselves, but soon replaced it with a steam unit. We found that the the mist-type did not add sufficient moisture to prevent me from having to supplement it with room humidifiers.

James,

This is easily proved wrong, from info already posted on the piano tech forum. Note the swings from 45% to 70%:
D-C thread with graphs

--Cy--

Two Desert Spring central units and a Dampp Chaser.

I rejected room units for their noise and (in the ultrasonic ones) the white dust. COlorado water has LOTS of mineral content as evidenced by the frequent cleaning of my central units. I use distilled water in the DC.

Also as an engineer, I chose to believe the school of thought that wood is porous, and the warmed, moistened air remains below the soundboard long enough to maybe do some good. I DO NOT believe as some have stated that there is a huge balance problem. First the DC will not overhumidify because it has an integrated hygrometer and will shut off, and second over time the moisture will permeate the wood. Usually the top of soundboards is heavily sealed anyway.

David Glynn: I asked the same question. The answer pointed out the obvious: the other bits of the piano won't get much help from a DC, but they also aren't as large, under such pressure, nor so difficult to replace if need be.

Finally - trivia: the two Steinway 9' grands on stage at DePauw University in Indiana (my daughter's college) each have DCs.

Hi all,...

I apologize in advance for hijacking this thread,... I was going to send a PM to Rich but I think other people may benefit from this question as well,...

Rich,... How can I tell if a humidifier is a "steam" type or "mist" type?

Our house's humidity swings in the past month is between 29% and 34%,... I'm thinking about adding the following bypass humidifier to my furnace,...

http://www.lennox.com/products/overview.asp?model=HCWB17

Is this a "steam" type or "mist" type humidifier?

Regards,

Robert

Michael, I am just curious about the amount of water that you use. Here in London the weather is very variable, but we get periods of anticyclonic weather in winter when the humidity might typically be 30-35%. The piano is in quite a large room (25x15 ft), and the room humidifier brings the room up to 50% with no problem. However, even in dry winter weather the humidifier does not use more than a gallon and a half per day. Your 4-5 gallons sounds an enormous amount! Or do you keep the door open, so that to some extent the humidifier is working on the whole house?

I have commented a number of times on this subject previously - but I will do this again. At our technician's recommendation, we use a whole house, flow through style humidifer. These are several hundred dollars to purchase and install. They remain somewhat dependent on furnace air circulation, but nothing like the old wick or drum style by-pass humidifiers especially since our furnace fan runs continually. They are basically self cleaning as water is constantly running through them; once a year maintenance is plenty. Even in the driest and coldest climates (like ours) a decent level of humidity can be managed if your house is well insulated. For example we run our humidifier to 40% without issue during the winter, but have R35 walls, triple glaze windows and an air-to-air exchanger. Creating a well balanced, steady environment in your home may be sufficient, or perhaps even superior protection to a D-C alone, and has a host of other benefits as well. Having both would likely be ideal, but I do like the fact that our situation is vitually maintenance free. RH at the piano varies from 38% to 47% depending on the season, which is probably an OK range. I believe the right answer depends on so many factors that I would engage a technician that you trust to discuss options, and then go to a HVAC specialist to see what they recommend based on your house and climate. There is rarely an easy or cheap way to solve home environment concerns.

I am afraid I find myself rather at a loss in this discussion, because many of the terms (“in-furnace, whole house humidifier “, “whole house, flow through style humidifier”, “wick or drum style by-pass humidifiers”, “furnace fan”) are alien to me!

Our house, like most in the UK, has central heating, with a boiler (“furnace”?) heating water which circulates through radiators in the rooms. Would I be correct in surmising that mdsalemi and SCCDoug have hot-air systems, where air is heated centrally and then ducted to the rooms? And that a humidifier can somehow be connected into such a system?

Lacking a hot-air distribution system, I have to rely on an evaporative room humidifier.

Michael, I was interested by this comment, which is quite different from my situation. With us, the outside RH is extremely relevant. In cold dry wintry weather, the humidifier runs at maximum output. On warmer damp days (like today), it does not run at all. Is this difference due to the different heating system? Maybe a hot-air system would always deliver dry air, whatever the weather, if no humidifier is installed?

Have you looked at whole house humidifiers, as in "part of my central heat"? We're having one installed and it was, surprisingly, cheap. $450 with 45% humidity, max. I asked, "Could we get 50% with $500?"

James,

I don't mean to offend you but, you have offended me. There is a very big difference between having an true knowledge and a complete understanding of a piano and it's working parts, what causes a piano to go out of tune and the best possible way to keep it in tune and closest to pitch than there is from having an bachlor's or masters degree in some other field that has nothing to do with pianos. You have your masters degree in your field whereas, we have our masters degree in our field. The field of piano technology.

You are completely out of line and very incorrect about how well Dampp Chaser systems work. Have you ever installed one? Have you ever seen just exactly what they do over the course of 15 years to a piano? Well, I have seen thousands of them working over the past 35 years and they work extremely well!

While we are all entitled to our opinions, and I'm certainly going to voice a very strong one here on this issue, we don't claim to tell you your business but yet, you seem to want to tell us ours and even insist that we're wrong. Yet, when we attempt to explain to you that they do indeed work, you refuse to listen. Why do you suppose that we know they work? From our many years of experience working with them, that's why.

When you claim to tell full time piano technicians who like myself, who has literally serviced tens of thousands of pianos over my life time with thousands of different Dampp Chaser systems installed in them that they do not work? You are 100% dead wrong sir. I highly suggest you go directly onto Dampp Chasers web site and look up the findings and intense studies that they have performed themselves over the course of many years along with what most piano manufacturer's have to say about them. If they didn't work, then the companies that build pianos like Steinway, Baldwin, Yamaha, Kawai and most other manufacturer's wouldn't recommend them.

As for concert grand's not having them? Again, you speak for a lack of knowledge about this.

In a college that I service for here in Grand Rapids, Michigan, we have 2 Steinway D's, both of which have a double Dampp Chaser system installed. Without these systems installed, as our humidity changes, the pitch and tune immediately also begins to change whereas, with these systems installed, the pitch of the piano stays very close to A/440 almost all of the time.

My college has several other Steinway B's and other larger grand pianos with Dampp Chaser systems installed in them as well. They all work as they should.

I have Yamaha's, Kawai's, Petrof's, Baldwin's, you name the brand piano and I have a system installed in it. If you had seen the piano before, and heard how badly out of tune the piano went from summer to winter WITHOUT the system installed and then, heard it afterwards, you would have a complete change of heart.

It is important to note that, these units work best only when the piano is kept closed when it is not in use. It is also extremley important just exactly how the Dampp Chaser system is placed within the piano.

Sorry to be so brash and so long but, as piano techs, we really do know what we're talking about here.