The unions that connect the in and out piping to my water heater have flat rubber gaskets that they don't have at any of my local pool supply stores. I did find an O ring that is working for now but it is a little bit thinner and I had to slightly stretch it to fit. I did find a perfect size O ring but it was slightly too thick to push into the groove that the original went into. The original is broken and a bit distorted but it is approximately 70mm in diameter while the gasket width is 2.7mm and its thickness is 2.2mm. Photos attached. Assistance will be appreciated, thanks. IMG_20190723_0601.jpgIMG_20190723_168.jpgIMG_20190723_0842.jpg