Szlumper was born in Westminster to Albert Szlumper, a Polish tailor, and his first wife, Eliza. He began his career with a London firm of engineers, and in 1853 was appointed surveyor to the county of Cardiganshire, a position in which he held for 25 years. In this position, he was often in correspondence and conflict with the local landowners, particularly John Waddingham, the then owner of the . His younger half-brother Alfred Weeks Szlumper was also a railway engineer.
On 31 December 1868, Szlumper was appointed Chief Engineer of the Whitland & Taf Vale Railway, having been recommended by business partner and Member of ParliamentDavid Davies. The W&TVR was closely aligned to the Pembroke and Tenby Railway, having a virtually common set of investors and board of directors. The P&TR also had close links to the Manchester and Milford Railway, which ran over the Szlumper engineered metals of the Carmarthen and Cardigan Railway to connect to Carmarthen station The W&TVR was driven by John Owen, the proprietor of some slate quarries near Glogue, and Szlumper agreed to see the construction of the railway for £50 per mile and £15 per mile for out of pocket expenses, and to deal with the preparation of all plans and sections for the necessary Parliamentary Bill. By 1868, Szlumper was engineer to the C&CR, M&MR, P&TR and the W&TVR. After an accident with a through LNWR train to Tenby, Szlumper rebuilt the stations at Tenby and Pembroke, and extended the P&TR further into Pembroke Dock, to allow larger trains to access the line from 3 August 1870. The M&MR promoted the benefits of the P&TR to access Pembroke Dock to its customers in the Midlands, but the relationship only prospered for three years after the P&TR ceased working east of Whitland station over the Great Western metals, from 31 July 1872. The board of the P&TR realised they needed to gain economies of scale, and so appointed the largest M&MR shareholder J.J.Barrow to their board on 31 August 1871. Barrow needed the stable income and docks of the P&TR as his own M&MR was suffering financially through lack of traffic from the Midlands to Wales. Barrow appointed A.C.Sheriff to the board of the P&TR in May 1872, the former Traffic Manager of the Oxford, Worcester and Wolverhampton Railway. Further developments had to wait until the formation of the P&TR and M&MR Joint Committee in 1879; but by this point the M&MR was totally insolvent and the GWR had developed its strength in West Wales. On 24 March 1873 the W&TR opened to Glogue, and by October 1874 to Crymmych Arms. During the period 1859 to 1876, the P&TR had seen three different chairmen, two secretaries and three engineers. Due to the insolvency of the M&MR, in June 1879 the board joint board of company to investigate the costs of the railway. Szlumper was paid a salary of £150 per annum by the M&MR, and £80 for the P&TR. The board felt Szlumper had not fulfilled his duties properly, particularly after incorrectly engineering the M&MR junction at Pencader which was investigated by the Railway Inspectorate. He was replaced by Lionel R. Woods, formerly of the North Eastern Railway, in December 1879. The W&TVR extension to Cardigan was completed on 31 August 1886, after the GWR had taken over the joint companies in 1881.
Szlumper married Mary Culliford in 1867 and had one son and two daughters. The family lived at Sandmarsh, Aberystwyth. After Szlumper's retirement from the role of surveyor of Cardiganshire, the family moved to Holmesdale Road in Richmond, Surrey, where he became Mayor twice. He was also a major benefactor of Darell Road School in Kew and was, for many years, president and patron of the Victoria Working Men's Club in Kew. A Master Freemason of the Jubilee Masters Lodge, No. 2712, and also a Past Master of Aberystwyth Lodge, No. 1072, his long-term friends included Mary of Teck, the Queen Consort of George V. Szlumper died on 27 October 1926 and is buried in Richmond Cemetery.
As Szlumper helped plan various lines running from or attaching to/joining with the South Wales Railway, he left in his collection of papers complete Ordnance Survey maps from 1896, in continuous length, showing the proposed routes of the railways from London to Swansea and its connections, and the proposed railway from London to Cardiff and its connections