| Heat Number - 1 | |||||
| Lane | Comp.No. | Name | YoB | Club | Time |
| 2 | 1 | Jonathan GBYLICZEK | 12 | Lincoln Vulcans SC | 3:59.87 |
| 3 | 3 | Luca HALLAM | 12 | Grantham SC | 3:50.31 |
| 4 | 5 | Cole COOPER | 12 | City of Linc Pentaqua SC | 3:46.52 |
| 5 | 4 | Oliver CLARKE | 12 | Deepings SC | 3:47.63 |
| 6 | 2 | Oliver WILKINSON | 12 | Lincoln Vulcans SC | 3:52.27 |
| Heat Number - 2 | |||||
| Lane | Comp.No. | Name | YoB | Club | Time |
| 1 | 7 | Francesco MONACO | 12 | South Lincs Competitive SC | 3:36.59 |
| 2 | 9 | Jacob GIFFORD | 10 | Lincoln Vulcans SC | 3:25.11 |
| 3 | 11 | Oliver GARNER | 10 | City of Linc Pentaqua SC | 3:21.09 |
| 4 | 13 | James THOMAS | 10 | Gainsborough Dolphins SC | 3:09.90 |
| 5 | 12 | Matthew TOMPKINSON | 09 | Louth Dolphins SC | 3:10.41 |
| 6 | 10 | Theo BACON | 10 | Grantham SC | 3:22.20 |
| 7 | 8 | Henry SEAGROATT | 11 | Louth Dolphins SC | 3:35.94 |
| 8 | 6 | Samuel NICHOLS | 12 | Grantham SC | 3:43.37 |
| Heat Number - 3 | |||||
| Lane | Comp.No. | Name | YoB | Club | Time |
| 1 | 15 | James NICHOLS | 09 | Grantham SC | 3:05.12 |
| 2 | 17 | Frank LAMB | 09 | South Lincs Competitive SC | 3:03.73 |
| 3 | 19 | Jake ADAMS | 07 | Louth Dolphins SC | 2:57.40 |
| 4 | 21 | Kieran NG | 10 | South Lincs Competitive SC | 2:55.67 |
| 5 | 20 | Ryan NORTON | 07 | Boston Amateur SC | 2:57.12 |
| 6 | 18 | Morgan FARRAR | 09 | City of Linc Pentaqua SC | 3:00.46 |
| 7 | 16 | Freddie TRAGNI | 09 | City of Linc Pentaqua SC | 3:03.95 |
| 8 | 14 | Archie FRENCH | 09 | Lincoln Vulcans SC | 3:06.27 |
| Heat Number - 4 | |||||
| Lane | Comp.No. | Name | YoB | Club | Time |
| 1 | 23 | Finnley DANBY | 06 | Boston Amateur SC | 2:54.40 |
| 2 | 25 | Matteo MONACO | 09 | South Lincs Competitive SC | 2:51.81 |
| 3 | 27 | Jack ZERAVICA | 08 | Grantham SC | 2:50.52 |
| 4 | 29 | Jack HUGHES | 07 | Lincoln Vulcans SC | 2:48.28 |
| 5 | 28 | Stefano FIORE | 07 | South Lincs Competitive SC | 2:50.09 |
| 6 | 26 | Hayden POTTS | 08 | Lincoln Vulcans SC | 2:51.71 |
| 7 | 24 | Jacob FISH | 09 | Grantham SC | 2:52.32 |
| 8 | 22 | Aidan FITZGIBBON | 08 | City of Linc Pentaqua SC | 2:54.46 |
| Heat Number - 5 | |||||
| Lane | Comp.No. | Name | YoB | Club | Time |
| 1 | 31 | Oscar GOLDSMITH | 08 | South Lincs Competitive SC | 2:41.21 |
| 2 | 33 | Alfie BISBY | 07 | South Lincs Competitive SC | 2:39.24 |
| 3 | 35 | Rico BRINGEMAN | 05 | South Lincs Competitive SC | 2:34.22 |
| 4 | 37 | Henry CRUST | 05 | City of Linc Pentaqua SC | 2:23.37 |
| 5 | 36 | George BERWICK | 03 | Grantham SC | 2:32.17 |
| 6 | 34 | Alex MANLEY | 92 | Lincoln Vulcans SC | 2:36.60 |
| 7 | 32 | Zach HOPKINSON | 09 | Grantham SC | 2:40.20 |
| 8 | 30 | Jacob BRIERS | 08 | Deepings SC | 2:47.01 |