Swansea Crown Court heard that Network Activity manager Graham Hughes stole more than £10,000 of kit between June 2011 and December 2012.
His haul included a water pump, generator, gas and heat detectors and digital cameras.
Hughes, aged 55 from Abergwili, worked as a Network Activity manager for the South West and was based in Clydach.
He had worked at the company for 30 years but has since lost his job.
Thisissouthwales reported that prosecutor Kevin Jones told the court that a series of anonymous letters to Welsh Water alerted them to the items for sale on Ebay.
Fraud officers found items similar to those used by the company being sold via an account linked to Hughes.
He pleaded guilty to theft.
In total they had cost £10,124 to the company but he had sold them for around half their value.
Hughes has since repaid the £10,000 to Welsh Water.
Judge Huw Davies said: “The tragedy of the situation is that you have lost your good character. You had worked for your employer for a very long time and reached a senior position.”
Judge Davies imposed a 16 week jail term, suspended for two years.
He was also ordered to pay £650 in costs.