Picasaweb's servers do not output standard headers for images.
That's why they won't appear in this forum automatically.
Try to right click any of the images in picasaweb and click 'View Image' and you'll note that most browsers won't display the photo 'inline'... they will attempt to download it directly as if it were a zip file or something.
This method of viewing photos is just a trick on google's part to prevent one from using google's servers to host images for their websites without visiting the picasaweb-site.
Here's an inline image from spapartsnet server:
That spa is about 11 years old at the most. It looks to have a gecko topside so the oldest you'd be looking at would be around 1996-7. I'd estimate about 375-400 gallons or so. It's just a guess.