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# Dear All, how to size hot water3

## Dear All, how to size hot water

(OP)
Dear All,

how to size hot water return pipe ? the common sizing method is to determine the heat loss from supply and return piping, but i don't know how to determine the heat loss for PPR and CPVC pipes?

### RE: Dear All, how to size hot water

Same way you size it for copper pipe.

Determine the heat loss per foot of pipe with(out) insulation and determine the flow rate that will enable you to provide enough flow to counteract this. Size the pipe for that flow rate.

### RE: Dear All, how to size hot water

(OP)
you mean to use the same table of heat loss for copper pipe with any pipe material PPR or CPVC

### RE: Dear All, how to size hot water

Maybe.

I never depend on tables without understanding what they represent.

As an exercise, you should use the thermal conductivity of the pipe material in question in the heat transfer equation to get real numbers. Then compare to the tabulated values.

If you are insulating the plastic pipe, the total heat loss will be comparable to that of insulated copper since the insulation provides enough resistance to heat flow that the difference in conductivity of the pipe material is insignificant.

If you are not insulating the pipe, then the difference in material will play out.

Since copper tubing and the plastic pipe material have essentially the same roughness (epsilon), there is not significant difference in the friction loss - but you do have to consider the difference in pipe inner diameter.

(OP)

### RE: Dear All, how to size hot water

Mr. Zoro

You can use 3Eplus to calculate the heat loss per linear ft for different pipe and insulation configurations. Its free.

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