Guys if you read the post, the reason the tank water heater was so expensive was due to the construction required to get his house up to code. I personally like my tank heater. If your changing from a tank to tankless there is alot of work to do. Moving water lines, moving gas lines (possibly upgrading gas line size too) and running a new intake/exhaust if using gas, upgrading the main service amps if using electric. Some things to consider Tank Heater Pros Costs less to replace in the future Easier to maintain (Tank water heaters are easy to flush out every year) Easier to install (dont have to upgrade gas line or main service amps) Gas water heater will still operate in power outage (electric will still have some hot water to use for a while till power kicks back on). Cons Not as efficient as tankless No Tax Credits Hot water limited by FHR (first hour rating) Tankless Heater Pros Unlimited hot water More efficient Saves space Cons Will cost more in the future to replace (there is no guarantee the tankless will last longer than a tank version, the heat exchanger can go bad and that is the most expensive part of the tankless) , Harder to maintain (you need to try to clean those tankless heaters out every year with a descaler so they stay working efficiently) Harder to install (upgrade gas line or main service amps) Tankless heaters have a limited throughoutput. While it is unlimited hot water, it can only supply so many gallons of hot water at a time Will not operate in a power outage. A tankless water heater is controlled by electronics whether the heater is gas or electric does not matter. Requires minimum gallons per minute from city water supply, some people have not been able to install due to that problem. Consumer reports note that users complain of inconsistant water temperatures. http://www.consumerreports.org/cro/appliances/heating-cooling-and-air/water-heaters/tankless-water-heaters/overview/tankless-water-heaters-ov.htm Another good site to look at: http://www.waterheaterrescue.com/pages/WHRpages/English/Longevity/tankless-water-heaters.html

Some valve bodies have an auto shut off feature which is designed to prevent scalding. If one side has no pressure, both sides are shut off inside the valve body. Or you dislodged some huge chunk of rust and it made its way to the shower valve. I can't see from here. Try dissembling the shower valve and flushing it out.

Those numbers are definitely gas. $2800 seems like a lot. Longevity is of course variable and paying more probably gets you greater longevity. I haven't looked in a while but Marathon sold ones that significantly outlasted average ones. The first question is what is your fuel? NG is cheap and Propane is not (well it is relatively cheap now but more variable). Next is - not sure where you heard that tankless is not good. I have my issues with tankless but they should be considered. I have one in a new rental townhome and the water takes a long time to get hot. That is an issue but doesn't have to be. Some of that is plumbing but some is the nature of tankless. But in general tankless is the goto for many. It is a lot cheaper than $2800 and gives you 96% typically. Third question is why not use electricity? Heat pump hot water heater makes sense in a lot of environments. But you need to have the room and sound isolation. Lastly, there is some value still for solar hot water if you are concerned about being a good steward for the environment. Best if you don't have room for heat pump hot water. It also will outlast a heat pump. We paid about $7k but got $5k in incentives so it was a minimal cost to us for a good 80 gal tank with install. When considering the options, I always think it is good to remember that gas can not be created in a renewable fashion but electricity can. Also many electric utilities offer rebates for highly efficient electric devices. Many would be surprised but there is a growing return to electric resistance type hot water heaters for this reason. Particularly POU devices that eliminate the wait (and waste) of distributing hot water. I am still trying to figure out Duke Energy's incentives but I think we may be going back to solar if the incentives are still there.

Hi @venexiano, I'm sorry I wasn't more clear. First let me say that I am making an assumption that your current setup only supplies domestic hot water and doesn't provide any space heating. I'm also assuming there aren't energy codes in your area that would dictate something different. If you want to do the most cost effective thing over the next 12 months with minimum investment. Replace the pump. The pump itself is $280+ tax and shipping. Having a plumber do it for $500 is reasonable. It would pay for itself in 5 months. Your 17 year old water tank will probably last at least 5 months that would break-even on the pump replacement. This is the lowest cost option, with a clearly defined break-even of 5 months. Do this. If you are looking to the future (what do I do when the 17 yo tank heater goes out?) Re-evaluate the entire setup with an eye on a hybrid electric heat pump water heater. These water heaters are not inexpensive to buy - but would cost less than replacing the existing tank heater with a unit similar to what you have now. (The existing unit is designed for solar storage - which adds to the cost). Hybrid electric water heaters have one of the lowest operating costs of any water heater - particularly when there's plenty of ambient heat to pull from. If you replace the existing tank with a hybrid electric heat pump heater then you could probably decommission the solar at that time. This would eliminate the small holding tank at the top, the pump, and the panels on the roof as a point of failure - dramatically simplifying things, future maintenance and costs. You seem to have an ideal setup for a hybrid electric water heater. A 50 gal heater would probably be just fine for a family of 4, but if you use a lot of hot water, a larger one could save you more in operating costs. If you go this route I would decommission the solar in stages: 1. Leave the panels in place but remove the top tank and pump. 2. Remove the roof panels when it makes sense. If you are looking to reduce energy usage / carbon footprint / etc. (You said this is not the case) Install the larger water heater to avoid it switching to electric resistance heat. Add PV solar when it makes sense. The new water heater will play nice with that setup.