For drain-water heat recovery, the three ThermoDrain units below are the relevant options in this product list, but their supplied descriptions do not confirm horizontal installation. Check the manufacturer’s installation requirements and your plumbing layout before choosing one. The two drain pans are water-management accessories, not heat recovery devices. The factory-installed PEX model may suit buyers seeking PEX connections; the expansion-fitting model lists a 41% efficiency claim; and the copper-fitting model is intended for solder connections.
| Product | Best suited for | Important distinction |
|---|---|---|
| TDH3320B-DR-PEX | Buyers seeking factory-installed PEX fittings | Compact design; installation details should be checked |
| TDH3320B-DR-EXP | Buyers seeking expansion-style PEX fittings | Lists 41% efficiency and copper construction |
| TDH3320B 3″x32″ | Buyers needing copper ports for solder connections | Described as a main drain stack system |
| 20 x 13 water heater drain pan | Buyers seeking a leak-management accessory | Does not recover heat |
| Camco tankless water heater drain pan | Tankless-heater owners seeking a drain pan | Does not recover heat |
ThermoDrain TDH3320B-DR-PEX
Best for: Buyers who want a drain-water heat recovery unit with factory-installed PEX fittings. Its listed features emphasize energy recovery from shower drain water and a compact form intended to fit different plumbing setups.
The product description says the unit is designed to reduce water-heating costs by recovering heat from wastewater. It also describes installation as straightforward and says the unit can integrate with existing plumbing without major renovations. Those are manufacturer-provided claims; actual installation requirements depend on the building’s drain and supply layout.
Why it was selected: It is one of the few products in the list explicitly identified as a drain-water heat recovery system. The PEX fittings are a useful differentiator for buyers planning a PEX-connected installation.
Limitation: The listing does not specify whether this model can be installed horizontally. Confirm the approved orientation, dimensions, and connection requirements before purchase. Do not assume that “compact” means it fits a particular horizontal drain run.
ThermoDrain TDH3320B-DR-EXP Copper Unit
Best for: Buyers considering a copper drain-water heat recovery unit with ASTM F1960 PEX fittings. The listing specifies copper construction and states a 41% efficiency figure.
This model is described as recovering heat from drain water to preheat incoming water. The manufacturer says this can increase the amount of hot water available for showering and help reduce energy costs. It also describes the unit as using thick, pure copper and lists third-party certifications for potable-water safety and energy efficiency. Buyers should review the product documentation for the scope and details of those claims.
Why it was selected: Its stated efficiency figure, copper construction, and named PEX fitting type make it easier to compare with the other recovery units. Choose it if those listed specifications match the planned plumbing design.
Limitation: The provided product details do not confirm horizontal installation. Its listed 41% efficiency should not be treated as a guaranteed result for every household or installation; performance depends on system conditions and the applicable test method.
ThermoDrain TDH3320B 3-Inch Main Drain Stack
Best for: Buyers whose system design calls for a main drain stack unit with 3/4-inch male copper fittings for solder connections.
The listing describes a 3-inch by 32-inch passive heat recovery system. It says the unit preheats incoming cold water using heat from shower wastewater and gives a third-party-verified thermal efficiency rating of 39.94% at standard flow rates. The product description also says it is engineered to meet U.S. energy-code requirements with a 40% efficiency baseline. Because the stated figure is 39.94%, verify the applicable code and documentation with the local authority or installer rather than assuming compliance.
Why it was selected: It is explicitly presented as a drain-water heat recovery product and provides dimensions, connection details, and a stated efficiency figure for comparison.
Limitation: The name and description identify it as a main drain stack system, not a horizontal unit. Confirm installation orientation and whether it suits the intended drain configuration before selecting it.
20 x 13-Inch Water Heater Drain Pan
Best for: Buyers looking for a water heater leak-management accessory with a drain valve and hose. The listed dimensions are 20 by 13 by 2.5 inches, and the product description also mentions a 3.55-inch side wall height.
The listing says the pan has welded corners intended to create a watertight seal and includes a flexible hose to direct water away. These features address water management around a heater; they do not transfer drain-water heat back into the incoming supply.
Why it was selected: It is an adjacent plumbing product from the supplied list that may be relevant when planning equipment protection alongside a water-heating project. It is included for comparison, not as a heat recovery option.
Limitation: A drain pan does not recover energy or replace a drain-water heat exchanger. Check the dimensions and drainage arrangement against the specific equipment and installation location.
Camco Tankless Water Heater Drain Pan
Best for: Tankless water heater owners seeking a pan with a PVC fitting. The listing says it is designed to fit most whole-house gas or electric units and can be convenient when flushing condensate during routine maintenance.
This accessory is intended to help protect finished surfaces from water associated with a heater leak and to support drainage during maintenance. It is not a drain-water heat recovery device and does not preheat incoming water.
Why it was selected: It is the other water-heater-related accessory in the provided product list. Its tankless focus and PVC fitting distinguish it from the larger pan above.
Limitation: “Most” does not guarantee a fit for every heater. Confirm the pan’s dimensions, fitting arrangement, and drainage needs before purchasing. Choose a heat recovery system separately if energy recovery is the goal.
Buying Guide: Choosing Drain Water Heat Recovery
Can a listed unit be installed horizontally?
Do not assume that a drain-water heat recovery unit works in every orientation. The three recovery product descriptions provided here do not confirm horizontal installation. Ask the manufacturer or a qualified plumber for the required orientation and installation instructions. A unit described as a main drain stack may be intended for a vertical configuration, but the product documentation should determine whether another layout is permitted.
How does drain-water heat recovery work?
A drain-water heat recovery system transfers some heat from warm wastewater—often shower water—to incoming cold water. Preheating the supply can reduce the temperature lift required from the water heater. The drain water and potable water remain separated within the system; check the unit’s technical documentation for construction and safety details.
Which connection type should I compare?
Match the product’s connection style to the planned plumbing work. The listed PEX model specifies factory-installed PEX fittings. The expansion-fitting model names ASTM F1960 PEX fittings. The 3-inch main drain stack model lists 3/4-inch male copper ports for solder connections. These connection descriptions are not interchangeable; have the installer confirm the required fittings and transition pieces.
How should efficiency claims be evaluated?
Compare efficiency figures only when their test conditions and measurement methods are clear. One listing states 41% efficiency, while another gives a third-party-verified 39.94% at standard flow rates. Those numbers are product claims, not promises of household savings. Ask for the complete test documentation, and check local code requirements with the relevant building authority.
What measurements and site details matter?
Before buying, measure the available pipe run and identify the drain diameter, water supply connections, access for installation, and the desired equipment orientation. Ask whether the unit needs a minimum vertical length or a particular relationship between the shower drain and incoming supply. The provided listings do not give enough information to verify fit in a specific horizontal installation.
Are drain pans an alternative to heat recovery?
No. A drain pan collects or directs water around a heater; it does not capture heat from wastewater. The two pans in this product list may serve water-management purposes, but they should not be compared with the three heat recovery systems as energy-saving substitutes.
Frequently Asked Questions
Which product in this list is confirmed for horizontal installation?
None of the supplied product descriptions confirms horizontal installation. Verify the approved orientation with the manufacturer before purchasing.
Which listed unit has PEX fittings?
The TDH3320B-DR-PEX listing specifies factory-installed PEX fittings. The TDH3320B-DR-EXP listing specifies ASTM F1960 PEX fittings.
Does a drain pan recover heat from shower water?
No. The water heater drain pans are accessories for managing water around a heater. They do not recover heat or preheat incoming water.
What does a stated efficiency percentage mean?
It is a product performance figure under specified conditions, not a guarantee of a particular household’s energy savings. Review the test method and conditions before comparing figures.
Should a plumber verify the installation plan?
Yes. A qualified plumber can check the drain layout, connection type, available space, and installation orientation against the manufacturer’s instructions and applicable local requirements.