I have a very old Merrill Y-1 hydrant that was leaking. The design of the hydrant head is different than the current Merrill Y-1 design depicted on the Merrill website, and I could not determine how to remove it nor what the internal configuration of the head looked like. I had numerous conversations with Nancy at Merrill who provided me with sufficient information to remove the head so I could replace the valve. Based upon her help, I ordered a new Y-41B Quad-Seal valve. However, when I received the valve, the installation instructions specifically noted that this valve was only used in hydrants manufactured after November 1978 and my hydrant is most likely a 1950's vintage. I therefore felt that I had wasted my money. However, I decided to pull the head and 8' rod anyway and was delighted to find that the new Quad-Seal valve was dimensionally the same as the old plunger valve on the rod, and when installed, did stop the leak. There are other rusted parts inside my existing Y-1 head that will need to be replaced (spring and spring retainer), and may order those separately or just purchase a new head. However, that causes another problem since Merrill changed the size of the cap screws to 3/8" from 1/4" and I will have to drill and tap the hydrant casing to accept the new screws.