Baseline: tub → pump → filter → chiller → tub, with unions and isolation valves for service. Keep the main loop large and verify actual chiller flow.
Recommended baseline diagram
Baseline loop. UV, ozone, bypasses and heaters change placement; always follow the equipment manufacturer’s required orientation and electrical instructions.
Three common cold plunge plumbing layouts
The same four core components can be arranged for different service needs. These are planning patterns, not substitutes for the pump, filter or chiller manual.
Simple DIY loop
Use this when the priority is low restriction and easy troubleshooting. Put unions around equipment that may need removal and keep the suction side of the pump simple.
Serviceable loop with isolation
This layout makes cartridge changes and equipment service easier without redesigning the hydraulic path. Valves should be clearly positioned so the chiller cannot accidentally run without adequate circulation.
Loop with optional treatment stage
UV, ozone and other treatment equipment can add pressure drop and may have specific flow/orientation requirements. Add them only after checking the manufacturer instructions and recalculating the loop.
Where to put valves and unions
Use a shutoff/isolation valve near the tub outlet if the vessel design allows safe service. Put unions on both sides of equipment that may be removed. Avoid placing a throttling valve where it can accidentally starve the chiller without a clear reason and flow verification.
When a bypass is useful
A bypass can allow equipment isolation, flow tuning or service, but it can also create a path that reduces flow through the chiller. If you add one, measure or model branch flow and label valve positions clearly.
Hose diameter and fittings
Keep the main loop as large as practical. A short 3/4-inch connection at a component is different from building the entire loop from long, restrictive 1/2-inch hose. Minimize unnecessary reducers and sharp fittings.
Adding UV, ozone or extra stages
Every device changes restriction and sometimes required orientation/contact time. Add it to the hydraulic model and follow the device manufacturer. ChillSizer does not make blanket sanitation claims from the presence of UV or ozone alone.
Commission the diagram, do not just copy it
After assembly, check leaks, purge air, verify return flow and compare it with the chiller minimum. A diagram is only a starting geometry; real performance depends on your pump and components.
Frequently asked questions
Should the pump go before the filter?
In many DIY loops yes, because the pump needs to push through the filter. Exact pump/filter/chiller instructions take priority.
Where should I put a flow meter?
Use a location where it measures the flow that actually passes through the chiller, respecting the meter’s required straight run/orientation.
Can I put the filter after the chiller?
Some systems may, but filtering before the heat exchanger is a practical baseline for keeping debris out. Follow manufacturer requirements.
Sources & data references
What is the basic DIY cold plunge plumbing order?
A common baseline is tub → pump → filter → chiller → tub. Treat that as a starting point, then follow the exact manuals and verify actual flow before enabling refrigeration.
Should I use 1/2-inch, 3/4-inch or 1-inch plumbing?
Use the largest practical internal diameter supported by the equipment. Larger plumbing usually reduces friction loss, especially on longer runs and higher-flow systems.
What to read next
Run your exact setup
Use your real tub volume, temperature target, climate, pump, filter and plumbing. ChillSizer checks thermal capacity and actual modeled flow together.
Open the System Designer