To the Surface and Operating the Pump are quests in Chapter 10, "Rough Waters", in Final Fantasy VII Remake, taking place in the Sewer System. Cloud Strife, Aerith Gainsborough, and Tifa Lockhart find an exit from the Sewer System to Sector 7, but in order to reach it, must drain the water storage tank to reach the ladder.
In the Primary Treatment room, the water tank must be drained to reach the ladder. From the starting position, use the stairs on the right to enter a control room, and after some dialogue, pull the lever. Following some more dialogue, the player is put in control of Aerith.
As Aerith, follow Tifa to a water pump and interact with it. This commences a minigame: move the up to have Aerith open the valve, then use repeatedly to have Tifa work the pump and expand the target range. After this, when prompted, wait for the needle to hit the target range, and then move the down once to have Aerith close the valve. After repeated attempts, Tifa will expand the target range more, making it simpler. Hit the target range three times to succeed. After this, return to Cloud and pull the lever again.
After this, the player retains control of Cloud Strife, and will have to fight a series of enemies. Heal up, and to exploit the upcoming enemies' weakness to Fire, equipping Fire Materia on any character; on Aerith this is optimal for spellcasting, on Tifa this is optimally used with the Elemental Materia, and Cloud can use either. Pairing the Healing Materia with Magnify Materia on one character can also be very helpful to heal all party members. If possible, pair the Binding Materia with Warding Materia on whichever character being controlled most often to reduce the effect of the Sleep debuff. Enemies here can also inflict Toad.
As Cloud, leave the pump and head out to the emptied canal, and several sahagins will appear. These enemies are best defeated using Fire Materia spells, or character abilities. Their jump attack should be guarded against at all costs, as it can deal significant damage. After defeating them, heal up and head down the ladder and proceed forward, where sahagins are fought along with blugus. Blugus are a higher priority to defeat as they can inflict sleep; destroy these first with character abilities and spells, them focus on the sahagins after, ensuring that the jump attacks from the sahagin are dodged. Head across the bridge and use the ladder up, after which more sahagins are fought. Guard against their jump attacks, and unleash spells and abilities when they are not airborne. Use abilities that pressure them to get more opportunities to attack when they are not airborne.
After defeating them, head forward and interact with the ladder. This commences a cutscene, following which the next quest, "A Train Wreck", begins.
Hard mode tips
As before, fire materia is ideal against the sahagins. As before, while Aerith can pair it with MP Absorption Materia or HP Absorption Materia and focus on spellcasting while using Arcane Ward, and Cloud or Tifa can either pair it with elemental or spellcast themselves from within Aerith's ward.
With First Strike Materia and ATB Boost Materia, Aerith can open every battle with Arcane Ward, followed by ATB Boost, and then use Fira to instantly stagger or destroy one of the sahagin, allowing Tifa and Cloud to finish them off. Since this is the final combat challenge of the chapter, there is no issue expending all MP here on all three characters. Beyond this, remain defensive and evasive to avoid the sahagin's attacks as before.