Have you been told that your piano is untunable by your tuner or technician? This is fairly common in older pianos, generally made before WW2, and usually means that the piano is dead. There is no easy way to tell someone this, so we usually say it's untunable. So what does this actually mean?
The first reason to condemn a piano is that the tuning pins no longer hold the tension of the strings. The tuner brings the string up to pitch, but when he or she lets go of the tuning wrench, the string goes flat again. This is because there is not enough friction in the pinblock to hold the strings tight. If only one note is like this, it may be repaired, but usually many notes are like this, and it's not worth repairing the whole section or even the whole piano.
Sometimes I will be called to service a piano and it may have loose tuning pins, but it doesn't always stop me from trying to tune it. Before I try, I'll give the piano a thorough exam, and the following are other reasons we find to put pianos to pasture.
Cracked bridges, or bridge caps that have come loose mean that the quality of the sound will be very poor, and if the bridge cap is unglued, there is no point in tuning the piano.
The bottom board is no longer screwed to the piano. The bottom board is the part that the pedals are attached to, and when you try and use the sustain pedal, nothing works! I have seen pianos where the pedals only stop when they reach the floor, and the whole bottom of the piano is being pushed down.
The action is beyond repair. There are felt pieces and wooden pieces and screws and very small pins and all of these have specific tolorences and amounts of resistance measured in grams, and many factors interfere with these things. Humidity and wear are the two main causes, but sometimes little critters are the culprits.
Soundboard cracks and rib separations can sometimes be ignored, but when many different things are wrong with the piano, then it is time to stop ignoring this issue. A crack large enough to slip a quarter into sideways is too large, and usually the ribs have become unglued as well. If all of these things are wrong, and they usually are all evident at the same time, then it's time to get rid of the instrument.
So what can you do? First, consider if you can spend the $25K starting price to rebuild the piano. If it has a lot of sentimental value, and you can afford it, than you may have the work done. If it's Steinway & Sons grand piano, it's probably worth rebuilding and passing down to your family. If you don't have either of these options, it's time to move on. Your technician may try to stop the bleeding, but in the long run you're throwing your money away, so save it for a new one!