A system for determining ash height in a filter is disclosed. The system may comprise a string, and a pressure source configured to propel a portion of the string down a channel of a filter. A method for determining ash height in a filter is also disclosed. The method may comprise propelling a portion of a string down a channel of a filter, and determining an ash height in the filter channel based on a measurement of the string inside the filter channel and a known length of a clean filter channel having no ash accumulation.