I found this Hot Water Heater Safety Tank at a Goodwill store. While its large for an RV (they make a much smaller one) the price was right so I decided to try it. I had to build a platform to rest it on and keep it clear of the pump. Installed a tee fitting and used flexible hose to connect everything up. The tank has 40 lb of pressure in the air bladder and dampens out the fluctuation of pressure in the water system.
The first shot is of the platform, the second of the "T" fitting and hoses.
The tank installed in its proper space and finally, a shot of the finished product under the dinette seat.
I was lucky it fit, since I hadn’t measured prior. The installation make a huge difference in pump noise and running time. Its now a low humm rather than the former ratcheting sound. Plus water pressure stays a lot more constant. These shots were made during the initial install. I had to modify the T filtting, the stell fittings leaked, so I went to brass fitttings and nipples with plenty of plumber’s tape. That worked fine, no leaks.