| Brand | Unbranded |
| Model | PE15 |
| MPN | PE15 |
| UPC | 754094660816 |
| Brand/Model Compatibility | PLUMBERS EDGE |
| Product Weight (lb.) | 5 lb |
| Product Depth (in.) | 13.5 in |
| Product Height (in.) | 8 in |
| Product Width (in.) | 8.5 in |
Boilers operate at low pressure to prevent from building when the water is heated. The system must have a place for the water to go that is the job of the expansion tank. Heated water pushes against the diaphragm which absorb the pressure when the water cools the air behind the diaphragm pushes the water back into the system.