into a central aperture in a bottom endcap 545 in operation the formation fluid typically a slurry of the fluid with some sand from the flow line enters the sand trap assembly by flowing through apertures 516 of the top endcap and around the screen 525 at this time the change in volume reduces the flow rate causing sand to precipitate to the bottom of the receptacle e g at 581 the formation fluid passes through the screen providing further filtering then the formation fluid absent the sand enters the top 531 of the stand pipe 530 and flows out through the bottom of the bottle into the water line which returns the formation fluid to the main flow line the upper seal valve 338 may be opened and sample chambers above the pump out may be filled by opening the upper seal valve any pressure drop occurring across the sand trap may be avoided unlike a gravel packed probe where sample quality is compromised due to a large pressure drop across the gravel pack it is not necessary to close the inlet to the sand trap before filling the sample chambers above the pump out sand from the sand trap will not flow back out the top of the sand trap because the upper pressure relief valve 315 will not allow fluid to displace what is already inside the receptacle the remaining bottles of the multisampler below the pump out may be filled with formation fluid by closing the upper seal valve closing the inlet to the sand trap and opening the valve to the desired sample bottle the sample bottle may then be filled.