Thermal Expansion
Determine if a check valve exists in the inlet
water line. Check with your local water
utility company.
..It.may.have.been.installed.
in.the.cold.water.line.as.a.separate.back.flow.
preventer,.or.it.may.be.part.of.a.pressure.
reducing.valve,.water.meter.or.water.softener ..
A.check.valve.located.in.the.cold.water.inlet.
line.can.cause.what.is.referred.to.as.a.
“closed
water system”
..A.cold.water.inlet.line.with.no.
check.valve.or.back.flow.prevention.device.is.
referred.to.as.an.
“open”
.water.system .
As.water.is.heated,.it.expands.in.volume.and.
creates.an.increase.in.the.pressure.within.the.
water.system ..This.action.is.referred.to.as.
“thermal expansion”
..In.an.
“open”
.water.
system,.expanding.water.which.exceeds.the.
capacity.of.the.water.heater.flows.back.into.
the.city.main.where.the.pressure.is.easily.
dissipated .
A.
“closed water system”
,.however,.prevents.
the.expanding.water.from.flowing.back.into.the.
main.supply.line,.and.the.result.of
“thermal
expansion”
.can.create.a.rapid.and.dangerous.
pressure.increase.in.the.water.heater.and.
system.piping ..This.rapid.pressure.increase.can.
quickly.reach.the.safety.setting.of.the.relief.
valve,.causing.it.to.operate.during.each.heating.
cycle ..Thermal.expansion,.and.the.resulting.
rapid,.and.repeated.expansion.and.contraction.
of.components.in.the.water.heater.and.piping.
system.can.cause.premature.failure.of.the.relief.
valve,.and.possibly.the.heater.itself ..Replacing.
the.relief.valve.
will not
.correct.the.problem!
The.suggested.method.of.controlling.thermal.
expansion.is.to.install.an.expansion.tank.in.
the.cold.water.line.between.the.water.heater.
and.the.check.valve.(see.illustration.below) ..
The.expansion.tank.is.designed.with.an.air.
cushion.built.in.that.compresses.as.the.system.
pressure.increases,.thereby.relieving.the.over.
pressure.condition.and.eliminating.the.repeated.
operation.of.the.relief.valve ..Other.methods.
of.controlling.thermal.expansion.are.also.
available ..Contact.your.installing.contractor,.
water.supplier.or.plumbing.inspector.for.
additional.information.regarding.this.subject .
Refer.to.the.illustration.below.for.suggested.
typical.installation ..The.installation.of.unions.
or.flexible.copper.connectors.is.recommended.
on.the.hot.and.cold.water.connections.so.that.
the.water.heater.may.be.easily.disconnected.
for.servicing.if.necessary ..The.HOT.and.COLD.
water.connections.are.clearly.marked.and.are.
3/4”.NPT.on.all.models ..Install.a.shut-off.valve.
in.the.cold.water.line.near.the.water.heater .
Water Supply Connections
IMPORTANT: Do not apply
heat to the HOT or COLD
water connections. If sweat
connections are used, sweat
tubing to adapter before
fitting adapter to the cold
water connections on heater.
Any heat applied to the cold
water supply fittings will
permanently damage the
dip tube and heat traps.
NOTICE: The National
Fuel Gas Code (NFGC)
mandates a manual
gas shut-off valve: See
(NFGC) for complete
instructions. Local codes
or plumbing authority
requirements may vary
from the instructions or
diagrams provided and
take precedent over these
instructions.
Vacuum Relief Valve
(Not Supplied)
If required, install per local codes
and valve manufacturer’s
instructions.
9
Heat.trap.
6”.minimum
Heat.trap.
6”.minimum
Union
To.gas.supply
Sediment.trap
Cap
Ground.joint.union
Drain.Pan.Pipe.
to.suitable.drain .
Drain.
valve
Relief.valve.discharge.
line.to.suitable.open.
drain .
To.cold.water.
supply
6”.Air.gap
Blower.assembly
1/4”.per.foot.maximum.slope.up.or.
down.for.horizontal.venting .
Auxiliary.catch.pan
Union
Anode
Vent.connector
Thermostatic.gas.valve
Jacket.door
Manual.gas.shut-off
Temperature.and.pressure.
relief.valve
Shut-off.valve
Shut-off.
valve
Thermal.expansion.
tank.(if.required)
Combustion.Air.
Inlet.Openings
Hot.water.outlet.to.
fixtures
Water.Heater.Jacket
Flammable.Vapor.Sensor
Typical Installation
Remote.Control
Transformer.Box.
(Remote.Control.Models.Only)
.....
(Optional)
