I recently found and purchased a Homark Beer engine. It was a little messy, but appeared to be in decent shape. I took it completely apart and cleaned it up. The seals and the piston were in surprisingly good shape. The John Guest swivel elbow on the output was cracked, but I found a replacement.
(If anyone ever needs the same part here's a link. Note that it's BSPT thread)http://www.freshwatersystems.com/p-2550-swivel-elbow-bspt-516-x-14-bspt.aspx
After putting the engine pack together I tested it with water and it works great, except for one thing. The back flow preventer doesn't work like it should. It looks like the diaphragm in the preventer is misshapen. It sort of works, however it allows some back flow. I've searched and searched for a replacement part. I've even tried to contact Beer Engine companies in the US and the UK, but never heard back.
Does anyone know where I might find a replacement part? I would greatly appreciate any advice or assistance in locating a replacement, or an alternative. Here's a picture of the item in question. Thanks.
(Not that it matters, but these photos were taken before the rebuild.)