recirc for potable tank

DD_5

I want to install a recirc pump that will loop through an electric tank (isolated to serve the recirc only).

How do you size for this? In my case I'm sending the heated water through approx 60' of 1" pex until it reduces to 3/4" then 1/2" pex return to the recirc. The only head will be about 6' to the ceiling.

Mark Eatherton

Height has nothing to do with it...

Unless you are actually lifting the water from a low place to a high place and the system is not pressurized. Common misconception there.



In order to determine what size of pump you need, you have to know the total developed length (include elbows at 3' of pipe length per), and how many GPMs you need to move. For the purposes of DHW circulation return, 1 to 2 GPM should be more than adequate.



Once you know your required flow, you have to determine how much DYNAMIC resistance to flow you will be developing. This is usually expressed in feet of head. In a circuit of this style, you add all of the pressure drops together for the different size pipes, then find a circulator that is capable of generating those feet of head, at the 1 to 2 GPM flow rate you are trying to maintain. Most tubing manufacturers give that information in the manuals. You should probably add a 25 % factor for the restrictive fittings if using PEX.



Probably the smallest pump you can find will be too big. The material of the pump body for THIS application should be either stainless steel or bronze. NOT the lesser expensive cast iron.



HTH



ME

DD_5

got it

fantastic. Thanx for the quick response. I'll look in the pex manual.