No but seriously I buy 500psi pumtec pump heads for about £125 and for that reason I dont bother to service them, I just get a replacement head, every 18- 24 months I imagne the 400 type is about the same money, thats unless you want the motor as well , they are about £200-250 plus vat but they last for years, I have one in my Scorpion that is 7 years old and still going strong
Stuart