Hot Water Recirculator questions

[jefferson17]

We're considering a hot water recirculator but have some concerns if one would really be right for us, and if so, really which one. We have 4 stories of living space plus a basement below. The top 2 levels are each 1 BR apts. The water heater is in the basement, close to the risers.

I like the idea of the Watts (Grundfos) model. The price is ok at under $200. BUT ... from what I've read their "comfort valve" that is installed at the furthest point is designed with failure in mind (plastic inside the metal), and would likely need to be replaced every 1-2 years - about $50.

For us that means it would be installed in our 4th floor apt, under a tenant's sink. We really do NOT want a Leak Risk up there. That would be very bad for us. Whatever we might consider must be strong and worry-free but also cost-effective. $200 is fine. $400-500 isn't.

Right now most showers are within 50' of the current electric water heater. One shower might be more like 75' away. We'll be changing to an indirect that will be a further 50' away, connected via PEX. The 2 upstairs showers (3rd and 4th floor) are on old uninsulated copper). So if we're going to do this, it needs to be on a timer, or we'll lose a lot of heat radiating out of the older copper pipes upstairs.

One other option, is to only have this type of thing circulating between the current water heater and where the new one will be - to avoid any additional times from what people are used to today (probably would add about 30 sec with an extra 50' of 3/4 pex once water heater is moved). We've got really good pressure here so that's not a concern - just volume/time). I think that I could readily plumb in a dedicated loop in the basement, and perhaps some kind of mixing valve, to allow convection to automatically do this, but I'm not sure which type of mixing valve would "do the trick".

Thanks for any advice and recommendations!

Jeff

 

[Jadnashua]

Depending on how the supply line is run, you may need more than one cross-over point. And, if you don't have a dedicated return line, you will be putting some at least warm water into the cold water supply line. Many tankless systems are not compatible out of the box with a recirculation system and it voids the warranty. The flow rate on most of them is fairly low, and may be at the trigger point for the tankless system's flow detector. It's easier with a tank.

There are at least a few failure modes for the crossover valve: stuck open, stuck closed, leaking. Leaking is probably the least likely.

I have a RediTemp system that has the pump and crossover built into it as a unit (they now make multiple versions, and they all may not work the same). The crossover valves are rated at 1M cycles, so should last at least awhile. The hassle (if you want to call it a hassle) with this type is you need power to plug it in which often is not there underneath a vanity, and it does take up some space there. I've not found it to be a problem. When I remodeled, I dropped another wire down and installed a receptacle underneath the counter of the vanity. If you have power, it's all of about a 10-minute, reversible easy job to install it. You just need pliers or a wrench to loosen and tighten some hoses to the existing faucet.

 

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[jefferson17]

I can do a dedicated return line but only so far - certainly inside the basement - to eliminate the extra 50' run when we move from our current electric water heater to the new indirect off a boiler.

You make a good point about a possible warranty issue w/ the indirect - I'll have to check w/ Burnham to see if that's an issue. I don't see why this might be the case but it certainly doesn't hurt to ask the question and check their warranty paperwork to make sure that I'm not just trusting someone's word on the phone. What we'll be doing is not a tankless - it'll be (likely) a 50 gallon indirect tank - powered by a new gas boiler.

As I'll be running PEX to the new water heater, it wouldn't be a big deal for me to add it in later, if need be but I'd like to consider the option right now during my planning stages.

 

[Jadnashua]

An indirect is no problem...only with (most?) tankless systems. Not sure how a dedicated partial return line would help - you'd still be using the cold lines as returns for the rest of the building and when it got to that new return line, it would just divide itself between the cold and the return. Suppose if you put a checkvalve in it, that may work, but there may be more than one branch. Now, if you could thread one all the way to the top and put the cross-over there, it would work fine.

The cross-overs, should you use one (needed without a dedicated return line) typically have a thermostatic valve in them so you don't warm the cold line up too far (many of them stop the cross-over when the hot reaches 105 or so, not full hot. The only one I know of that has a user adjustable aquastat is the RedyTemp unit. I have mine set so it is just warm at the vanity. Everything else is closer to the WH, so it's hotter. I find that if I flush the toilet, it purges most of the warm water from the cold line at the vanity, so it doesn't take long to get the building's 'normal' cold water temp, and hot is only a very short time (the shower is closer, and is almost immediate).

 

[jefferson17]

If we put a crossover at the front of the basement (current location of water heater and near risers) then we eliminate extra wait time that would be added when we install the new indirect in the rear of the basement. But ... that's only a partial solution.

I guess I really do need to figure out how tough it would be to do a dedicated return. If that can be done, then we're set. Otherwise, I'm not sure that this makes sense.

Worst case, I can always add in that basement loop ...