Home run w/PEX how about a heat circulating pump?

[dirk_411]

I'm just buying some of the parts and pieces for a home plumbing upgrade on a 22 year old home.

as of now I'm going from a copper trunk and branch and will be converting to a home run set up. I'm also adding the pside kick csv.

something popped into my head, how about a circulation pump on the hot water? just thought it would be nice to have hot water faster. Guess I would have a sub manifold down at the end of my bulk head which is where both bathrooms are and the kitchen sink. I think from there I would have the return line back to the water tank... correct me if wrong. I have a reheem, not sure on model. it's about 65" tall and has titanium elements I believe.

few questions. would this cause my hot water tank to run A LOT more? I don't believe a 120 volt circulation pump would cost a lot of money to run! also how would you have it set up? on temperature or time???? or run it constantly?

feedback appreciated, I'm an amateur

 

[Jadnashua]

There are lots of kits out there that have the pump, controls, valves etc. that you would need. Yes, you can cobble your own up. Note, probably the bigger expense in potable water recirculation is the requirement that the pump be either bronze or stainless steel, you cannot use a much cheaper cast iron body or impeller for your circulator like is commonly used in hydronic heating systems - too much oxygen in the water - it will destroy it and leach out minerals you don't want circulating in your water.

It somewhat depends on whether your water heater has a tempering valve or not, where you should best connect the return line. If you don't have a tempering valve, you can modify the drain valve to allow you to add a T and insert it there into the bottom of the tank. There is at least one tempering valve for a WH that comes with a port to accommodate recirculation. Note, on many tempering valves, when recirculating, since there's actually no cold water going into the tank to replace what comes out, you can get into a situation where all you get out of the tank is untempered, potentially very hot, water that could end up filling the supply line rather than tempered water.

On many systems, the pump actually runs constantly (or maybe a timer), and you use some sort of temperature sensing device to stop or slow the recirculation once the point of use is hot (or warm - some are adjustable). On some, it starts and stops the pump.

Many of the kits you can buy are designed for retrofit, and do not use a dedicated return line, but they can also be used with a dedicated return (verses using the cold line) by slightly changing how they are connected...this is often discussed in the installation manual. The one I have was retrofit (no easy way to run a dedicated return), and it fits underneath the sink of the furthest point from the WH. As a result, everything before it gets hot, while I have it set to be warm there (with hot close behind if you really need full hot). IOW, mine shuts things off 'early'. Most shut down when the water gets to about 105-degrees or so, so that's probably lower than your supply. SOme are adjustable. Keeping the supply line warm verses full hot can save some on radiation losses. You should try to insulate all hot lines if you're going to be repiping your house.