That makes a simple quaternary search possible, in fact, and enables the space to be exhausted within 4 hours.

Start by putting in requests for 150, 100, 50

-If 150 hit (so we are in [150,200]), then the other two necessarily also hit. 300 has been drained, and 150-300 may be left overall.

Use the second hour to put in requests for 188, 175, 162 in that order. Note that there cannot possibly be enough water for more than one of these to hit.

--If 188 hit (so we are in [188,200]), then 488 has been drained, and 76-112 is left.

Use the third hour to put in requests for 103, 94, 85. Again, only one of these at most will be successful.

---If 103 hit, then 591 has been drained, so the tanks must hold at least 197 to have that capacity in the first place.

Use the fourth hour to request 9, 6, 3. Whichever one was successful (if any) can be added to 591, then that figure divided by 3 will give the capacity.

---If 103 didn't hit, but 94 or 85 did, then the bounds have been reduced to just three possible numbers, either [194,196] or [191,193].

Make just two requests in the fourth hour, at 6 and 3. This will be enough to disambiguate the possibilities.

---If even 85 didn't hit, we must be in [188,190], and 76-82 is left.

Use the fourth hour to request 82 and 79. A hit on either of these reveals 190 or 189 respectively; if neither hits then the answer is 188.

--If 188 didn't hit, the other two tests will reveal whether we are in [175,187], [162,174], or [150,161]. All of these intervals have fewer than 16 possibilities, so they can be distinguished within two more rounds of tests along similar lines to the above.

---[175,187] means 475 has been drained, and 50-86 is left. Request 80, 71, 62 at hour 3, then usually 6, 3 at hour 4 (59, 56, 53 if all miss)

---[162,174] means 462 has been drained, and 24-60 is left. Request 54, 45, 36 at hour 3, then usually 6, 3 at hour 4 (33, 30, 27 if all miss)

---[150,161] means 300 has been drained, and 150-183 is left. Hour 3 is then 159 (follow-up if it hits: 24, 21), 156 (if it hits: 18, 15), 153 (if it hits: 12, 9; if it misses: 152, 151).

-If 150 didn't hit, the other two tests will reveal whether we are in [100,149], [50,99], or [0,49]. All of these intervals have fewer than 64 possibilities, so they can be distinguished within three more rounds of tests. Depending on the specific numbers encountered so far, it will be possible to select a set of quartiles based on either the total amount drained or the maximum capacity. Just checking all the remaining numbers to make sure there are no peculiarities that make it impossible to disambiguate properly:

--[100,149]: 150 drained, 150-297 left; hour 2: 137, 125, 112

--This second round actually gives us a bit more information than the [150,200] case, since it's possible for round 2 test 1 to hit while still leaving enough left for one of the other tests to hit. So there are really 6 cases now.

---If 137 and 125 both hit, then we are in [138,149] with 412 drained and 2-35 left. Hour 3: 29, 20, 11; hour 4: 6, 3 (this works even if all miss and the disambiguation is between 8, 5, 2)

---If 137 and 112 both hit, then the answer is 137. (137 can't be the only hit with these numbers.)

---If 125 and 112 both hit, then we are in [129,136] with 0-21 left. Guess 18, 12, 6 in hour 3, and no matter what the outcome of this is, it will be narrowed down to two possibilities which can be distinguished by checking for 3 alone on the fourth round.

---If 125 hit but 112 didn't, then we are in [125,128] with 100-109 left. This case can be fully discerned by hour 3, guessing 109, 106, 103.

---[112,124]: 262 drained, 74-110 left; hour 3: 104, 95, 86; hour 4: 6, 3 (or 83, 80, 77 if all miss)

---[100,111]: 150 drained, 150-183 left; hour 3: 109 (then 74, 71), 106 (then 68, 65), 103 (then 62, 59) (102, 101 if all miss)

--[50,99]: 50 drained, 100-247 left; hour 2: 87, 75, 62

---If all three numbers hit, we are in [92,99] with 274 drained and 2-23 left. Hour 3: 20, 14, 8; hour 4: a single test for 3

---If just 87 and 75 hit, we are in [87,91] with 212 drained and 49-61 left. Hour 3: 61, 58, 55; hour 4 is only necessary if all miss and can be a single test for 52

---[75,86]: 187 drained (since 62 will also hit), 38-71 left; hour 3: 65, 56, 47; hour 4: 6, 3 (or 44, 41 if all miss)

---[62,74]: 112 drained, 74-110 left; hour 3: 72 (then 38, 35), 69 (then 32, 29), 66 (then 26, 23) (65, 64, 63 if all miss)

---[50,61]: 50 drained, 100-133 left; hour 3: 59 (then 28, 25), 56 (then 15, 12), 53 (then 55, 54) (52, 51 if all miss)

--[0,49]: 0 drained; hour 2: 37, 25, 12

---[37,49]: 74 drained, 37-73 left; hour 3: 47 (then 26, 23), 44 (then 20, 17), 41 (then 14, 11) (40, 39, 38 if all miss)

---[25,37]: 37 drained, 38-74 left; hour 3: 35 (then 9, 6), 31 (then 6, 3; answer is automatically 31 if 28 didn't hit), 28 (then 25, 22) (27, 26 if all miss)

---[12,24]: 12 drained, 24-60 left; hour 3: 21 (then 6, 3; answer is automatically 21 if 15 didn't hit), 18 (then 15, 12), 15 (then 17, 16) (14, 13 if all miss)

---[0,11]: 0 drained; hour 3: 9 (then 11, 10), 6 (then 8, 7), 3 (then 5, 4) (2, 1 if all miss)