Rheem 240V Heating Chamber RTEX-13 Residential Tankless Water Heater, GRAY

Rheem 240V Heating Chamber RTEX-13 Residential Tankless Water Heater, GRAYDelivered Nov 11, 2021TLDR: It's all about the GPMAbout 2 months in and no problems so far. This is my 1st tankless and quite happy with it. Doesn't take any longer to get hot water than it did with the tanked one. A few seconds depending on which side of the house you're on and a moment to settle as the pipe it's traveling through warms up. I was a little on the fence about the wattage and really didn't fancy needing two 240 lines for the next size up, but this did the trick. I've read some stuff saying 13kw wouldn't be up to the task of a hot shower in the northern states but took a chance and it's working just fine. That being said if the GPM is too much it wouldn't keep up, but it's more than enough for a very hot shower at just over 1 GPM, maybe 1.5 GPM total flow. It will do just under 1 GPM scalding injury hot with no cold water mixed in, somewhere between 1~1.5 GPM total flow with a little cold water in the mix for extremely hot shower hot.Some data to clarify... In PA just north of Philly, currently mid January and it's been pretty cold, 20 degrees most nights recently but it's dipped to 10, and I'm on frigid cold well water, and getting a hot shower I still need to mix in a some cold water or it's hot enough to burn you. So plenty good. Hot water heater to shower is roughly a 40~50 foot run through 3/4" pex in an unfinished unheated basement then down to 1/2" copper right at the bathroom and I get just under 1 GPM with the hot water valve wide open (after some previous adjustments to the flow rates on the feed lines)... 1 gallon in 1.18 minutes whatever that equates to. Now I did meter the hot water to everywhere but the washing machine via valves in the basement a few years back and that's working to my advantage now. I was dealing with an annoying ex-girlfriend who would run the hot water wide open and act like there was a problem with the heater or plumbing when she used up 40 gallons of hot water in under 10 minutes (with the tanked unit), or the water wasn't getting hot enough while she was blasting 4 GPM of cold water. And her disdain for logic and reason necessitated me finding a way to idiot-proof the situation. So my system is capable of delivering water much faster. Keep in mind I have a septic system as well so all this ridiculous water use was going into the back yard ready to overload my leech field.But regardless my typical routine (even when I had the tank unit and doing the same now) is open the hot water valve a little more than half way, give it a sec to get up to temp, then mix in just enough cold water so it's not going to put me in the burn ward. If you think I don't like hot showers it's hot enough to turn my normal Scottish pallor red and steam up the bathroom like a sauna. BUT it's not some kind of deluge GPM-wise, and I've adjusted the water like I have a functioning brain. Bathroom shower, sink, and kitchen sink will get hot enough to be steaming and scald you with the hot water valves full open which is (adjusted to) around 1 GPM +/- .And also the washing machine, which has not been throttled in any way, does not get fully hot. It could if I metered the hot water a little bit but I'm up in the air on steaming hot water in the washer but it taking a little longer, vs. just leaving it as is with warm water and it finishing quicker. Anyway, too many GPM and the 13kw heater can't heat it fast enough to keep up. But it does a more than acceptable job, even in PA winter, if you're not a glutton with the water.If you need to use more than one fixture at a time and expect more than lukewarm water, especially if one of them is a shower, this is likely not gonna cut it by itself. If you have a very high flow situation like a waterfall or rain type shower head, and/or have one of those stupid single handle valves that doesn't give you any indication of how the hot and cold are being mixed, and/or you have people who can't process mixing the hot and cold water in a sense-making way, you may want to go a step up to at least 18kw or more for full house, or maybe a 13kw main and another small one right at the bathroom to boost it. If you can live with just under 1 GPM scalding hot water, just over 1 GPM mixed hot water for a shower, 2 or 3 GPM of warm water, then you should be ok with 13kw.If I was to have one complaint with this unit it's that it needs too much flow before it kicks on. For example if I just want to wash my hands real quick and don't want ice cold water and don't need tremendous water flow, my typical opening of hot and cold valves like a quarter turn wont be enough flow to trigger the hot water heater to kick on. It won't come on till the hot water valve gets close to halfway open. Haven't looked into if that's adjustable or not but don't believe it is.Aside from that build quality is about what you'd expect these days, and by that I mean marginally acceptable at best. I really like the stainless heating tubes, being that I have acidic well water, but I have a feeling they're probably 304 rather than more corrosion resistant 316. And they screwed up corrosion resistance putting failure prone (when it comes to acidic water) brass in the mix anyway. But end to end 316 stainless units don't exist to my knowledge. "We can't design things for extreme cases like acidic or hard water!" ... Yes you can, very easily, you just want to make disposable crap so we need to buy more. Could you imagine buying one of these that would last forever no matter your water type and just having to replace the elements and flow sensor every few years, maybe clean some scale out of it if you had a lot of minerals? And some of the comparable units had copper tubes which would be far worse than 304 and brass, so not bad for what's available. And one thing I love about these is they are so small and light and now that the wiring's re-done it will be a breeze to swap out in a few years once my water eats it up. No more pumping out a 40 gallon tank and humping the heavy pieces of crap in and out of my basement :)And I feel I should qualify I'm really not some kind of water conservation nut. It's just most of my life having wells and septic systems you're much more in touch with where you're water's coming from and where the waste is going. It's great to have no water or sewer bills and be self sufficient, but I'm responsible for them, and both are expensive nightmares with direct and immediate impact if something goes wrong. It just makes sense to use what you need and respect the system. No water source is limitless and waste doesn't just magically disappear.

The Rheem RTEX-13 tankless water heater has been fantastic for my home. It heats water quickly and consistently, providing endless hot water without the wait or waste of a traditional tank system. The 240V heating chamber ensures strong, reliable performance even during high-demand times.Installation was straightforward, and the compact, gray design fits perfectly in small spaces, freeing up room in my utility area. It’s energy-efficient, helping reduce my utility bills while delivering hot water on demand.If you want a dependable, space-saving water heater that works great and lasts, the Rheem RTEX-13 is an excellent choice. Highly recommend

So far so good. Haven't used it for a shower yet but gets hot for the laundry. Love the smaller space it uses than the huge old water heater we had. Further testing will provide favorable, I'm sure.

It’s great for a small amount of lines running from it or a small house or camper

I bought the 13 KV model, it works great. Replaced a 52 gallon regular water heater and this tankless one works as good or better than the old one. It is small, about the size of a shoe box. I have a well, and water temp this time of year from the well is very cold but this unit does fine. Also with a well the water pressure varies a lot and is kind of low, 30 to 50 PSI, so you can only use one hot water source at a time. I have a big house, kitchen sink is about 70 feet from the water heater but water is very hot at the sink, it just takes awhile to get there. I had to make several adjustments to temp, as water was too hot, right now temp is set to 129, still a little too hot at times but works for doing dishes and pans in kitchen sink.The smaller units like mine, 13 KV, have 1/2 inch fine threaded inlet and outlet, but it comes with a 1/2 inch fine to coarse adapter. Also most hot water fittings and pipes are 3/4 inch, so you need to get an adapter if you have 3/4 inch pipes.Price was great too, $30 less than at HD for same unit.Unit requires number 6/2 wire, which is not cheap, plus a 60 amp breaker.Very happy with this tankless water heater, should have changed sooner.

Not even 2 years after install the product failed and deteriorated to the point it's unusable. No help when calling the company for help or warranty information.