Slantfin combicat turning boiler on when cold water is shut off

spacoli

Hi,



I have a Slant fin Combi Cat instant hot water maker. When using the cold water then turning  the cold water off  it activates the flow switch turning the boiler on for maybe 10 seconds. I thought it was because bad/old plumbing, but I had since run all new supply line and it still does it (not as offen as it did)



Any ideas what is causing this or how to remedy the problem?



Thanks