Water Tanks and Plumbing: Weight, Placement and Drainage
Water is the heaviest thing most mobile operations carry, and where the tank sits changes how the trailer tows.
September 8, 2026 · 5 min read
Detailing, grooming, food service and pressure washing all need water on board. The plumbing is straightforward; the weight is the design constraint.
Water is heavy
A full tank is a substantial load, and unlike most cargo it moves — water sloshes, and a partially full tank shifts weight while you drive.
- Size the tank to the work you actually do between refills, not to the largest that fits.
- Place it low and near the axles. Our load balancing guide explains why that matters for handling.
- Baffled tanks reduce sloshing considerably and are worth specifying.
- Check the numbers against the trailer's GVWR — this is one of the builds where weight rating is the real limit.
Fresh, grey and where each goes
- **Fresh tank** — sized to the day's work, filled before you leave.
- **Grey water** — this is the one under-planned most often. Used water has to be captured and disposed of properly. You cannot discharge it onto a customer's property, and requirements vary by jurisdiction and by what is in the water.
- **Both tanks change the weight balance as they fill and empty**, in opposite directions, which is worth thinking about.
The system
- 1Tank, with a fill point that is accessible from outside.
- 2Pump, sized to the flow and pressure you need.
- 3Filter, before the pump.
- 4Water heater if the work requires it — this is a significant power draw. See our generator and power guide.
- 5Distribution to the outlets you need.
- 6Drain and winterisation points, so the system can be emptied.
Freezing
South Georgia freezes are occasional and they do happen. A plumbing system that cannot be drained will eventually be damaged by one. Build in low-point drains and know the routine — our long-term storage guide covers the off-season.
Access for service
Pumps fail, filters need changing and connections need tightening. A system built where nothing can be reached is a system that becomes a problem.
Plan access panels and service clearance at build time rather than discovering the issue later.
Tell us the operation
Tank size, heater or not, and how many stops between refills — those three answers determine most of the build. Call (800) 281-5084.
Frequently Asked
How big a water tank do I need?+
Sized to the work you actually do between refills rather than the largest that fits. Water is heavy and a bigger tank eats into the trailer's payload, so the GVWR usually decides this before floor space does.
Where should a water tank be mounted?+
Low and near the axles, for handling. A baffled tank is worth specifying because water sloshes, and a partially full tank shifts weight while you drive.
What do I do with grey water?+
It has to be captured and disposed of properly — you cannot discharge it onto a customer's property. Requirements vary by jurisdiction and by what is in the water, so confirm what applies before building around an assumption.
Ready to roll?
200+ trailers in stock in Douglas, GA. Financing for all credit types.
