Plumbers were called out “weekly” to drainage problems at an ageing Chester hospital building where nurse Lucy Letby allegedly attacked 17 children.

Letby, 33, previously told jurors that the Countess of Chester Hospital’s neonatal unit had problems with “raw sewage” coming out of some of the sinks.

She said it was a “potentially” unsafe environment “if the unit is dirty and staff are unable to wash their hands properly”.

Letby, of Hereford, denies the murders of seven babies and the attempted murders of 10 others on the neonatal unit between June 2015 and June 2016.

On Wednesday, June 14, hospital estates plumber Lorenzo Mansutti told Manchester Crown Court about an incident in 2015 or 2016 when “foul water” came up a wash basin in nursery one.

He said that human waste or sewage came into the intensive care room from the drains of a ward above but he could not recall the exact date.

Mr Mansutti said there were issues with the drainage system at the hospital’s women and children’s building which he said was built in the late 1960s and opened in the 1970s.

Asked by Ben Myers KC, defending, how often he was called out for “these sort of issues” in 2015 and 2016, Mr Mansutti replied: “For the whole building it was maybe weekly.”

The court heard that plumbers were also called out to a flood in the neonatal unit in October 2015 and another flood in January 2016 in nursery four caused by white cloth forced down a plughole.

In March 2016 urgent work was required to rectify a blocked sink in nursery two and in a kitchen, while various plumbing checks were completed in the unit in early July 2016.

Prosecutor Nick Johnson KC asked the witness: “Does it come to this, that this area of the hospital at the time was quite old and had the occasional plumbing problems?”

“Yes,” said Mr Mansutti.

Mr Johnson said: “A lot of problems are caused by adults putting things down the sink that should not go down there?”

Mr Mansutti: “That’s one of the reasons.”

Mr Mansutti told the court there were back-up procedures for handwashing facilities in the event of sink blockages on the neonatal unit.

He agreed with Mr Johnson there was no repeat of the sewage incident in nursery one.

He said: “We did some work after to make sure it did not happen again.”

No further witnesses were called on Wednesday as Mr Myers closed the case for the defence.

The jury of eight women and four men were told by trial judge Mr Justice Goss that he will begin summing up the case on Thursday, June 15, and that closing speeches from the prosecution and defence will follow from next week.

Letby, who gave evidence for 14 days, denies all the allegations.

The trial continues on Thursday.