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3/4 water supply with 2 1/2"

I would like to supply my water heater with two 1/2" lines (one hot one cold)into one 3/4" then into the water heater. The reason for this is during the winter my hot water comes from a coil that runs through the boiler, in the summer it comes from an electric water heater. The problem is the "winter" hot water comes from 1/2" lines and the hot water flow is slow at the tub or shower. So during the winter I want have the so called free hot water run into the electric water heater along with another 1/2" of cold to keep the 3/4" supply line flow proper. My thinking here is it may help the electric heater to work less. I believe they don't make a copper "Y" so I would have to go with a "T" fitting with one 3/4 and two 1/2" ends. Providing both 1/2" lines have equal pressure would one line get an advantage or would the water be mixed equally regardless of which end they come in from? Is 1/2" okay or should I use reducers so they are 3/8" & 3/8" instead? :confused:

Re: 3/4 water supply with 2 1/2"

I would like to point out that there is no free heat in this system, the water is taking heat produced by the boiler or heat produced by the elements in the water heater.
Also you would need anti-back flow valves and if one source is higher pressure than the other it would simply close the back flow valve and you would only have water from one source or the other. With only ½" feeds you would have a lot of trouble maintaining pressure at the shower if someone turns on the hot at a sink.

Re: 3/4 water supply with 2 1/2"

Why don't you repipe the boiler supply and hot to 3/4" to pick up the volume that you want. The way you've described it you'll need a way to proportion the flow and that will retard your volume and your back where you started. Hope it makes sense to you.

Re: 3/4 water supply with 2 1/2"


First, be thankful you have a boiler----they are powerful enough so that they can be used to make all the domestic hot water you need.

The boilers that come with a "domestic coil" produce one or two gallons of hot water at a time (because that's all the internal copper coil holds) ---if you have hard water, they usually cake up with calcium & deliver even less hot water with low flow.

We've always used a 40 gal. indirect hot water heater in conjunction with the boiler to provide adequate hot water----these cost $700 but are well worth it if you already have the boiler----it's installed as another zone off the boiler & is allowed to run even in summer, with low use of fuel.

This would allow you to get rid of the elec. HWH.

The only other option would be to try & clean the boiler coil, or have it replaced---both are liable to cost ~$500---only to have it cake up again if you have hard water.

Re: 3/4 water supply with 2 1/2"

Thanks to every one for all the advice. I will probably scrub the whole idea. I was thinking of something "in the meantime" we are doing the roof and then the kitchen. Adding an indirect system is what we will eventually end up with but I was just looking to aid what I have for now.

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