KTI Hydraulic Reservoir Sizing — Pick the Right Dump Trailer Tank
Size the reservoir so it still reads about half full with the cylinder fully extended — usable tank volume should be roughly twice your cylinder's oil demand. Then confirm the tank's length fits your frame: KTI poly tanks run from 8.00" (3 qt) to 24.88" (14 qt).
Why Reservoir Size Matters
An undersized reservoir causes the most preventable dump trailer failure there is. As the cylinder extends it swallows oil from the tank; if the level drops below the pump's pickup, the pump pulls air, cavitates, and the bed gets spongy and slow. Do it enough times and cavitation kills the pump. The fix costs nothing at ordering time: match usable tank volume to your cylinder.
With the cylinder fully extended, the reservoir must still be about half full. If yours drops below half at full lift, the tank is undersized for the cylinder — upsize before it becomes a pump replacement.
KTI Poly Reservoir Dimensions — Factory Catalog Data
| Tank | Usable Volume (Horizontal) | Length "A" | Availability |
|---|---|---|---|
| 8181-35 | 3 QT | 8.00" | 3-Qt kit 8181-35-K |
| 8181-5 | 4 QT | 10.50" | Special order |
| 8181-6 | 6 QT | 13.25" | Tank · Kit |
| 8282-8 | 8 QT | 17.32" | Special order |
| 8282-10 | 10 QT | 20.00" | 10-Qt kit 8282-10-K |
| 8181-14 | 14 QT | 24.88" | 14-Qt kit 8181-14-K |
| 8484-16 | 12.25 QT (3.06 gal) | Square format | Square kit 8484-16-K |
Length "A" is the tank body length. The 14-quart tank needs over two feet of straight frame clearance plus room to pull the tank for service — measure before you upsize.
Sizing to Your Cylinder
- Find your cylinder's oil demand: bore area × stroke. A typical 3.5" × 30" single-acting dump cylinder swallows roughly 1.25 gallons (5 quarts) at full extension.
- Apply the rule: usable tank volume ≈ 2× that demand — the 5-quart example wants at least a 10-quart usable tank... but note KTI rates usable volume with the tank horizontal, which is already conservative.
- Scissor hoists and dual cylinders: add the demand of every cylinder fed by the tank.
- When between sizes, go up. Extra oil runs cooler and tolerates a slow leak longer.
Kits vs. Bare Tanks
The -K kits include the tank plus mounting hardware and fittings — the straight swap when you're replacing a cracked or sun-brittled poly tank on an existing KTI unit. Keep a spare Q2-4113 reservoir O-ring and 25-3 breather cap on the shelf; those are the two parts most often damaged during a tank swap.
After the Swap
- Fill to about 1" from the top with the cylinder retracted — see KTI's fluid recommendations for what to pour in.
- Run the official bleed cycle to purge air before the first loaded lift.
