astridh -- my husband is better suited to answering your question but from what I remember him telling me: RO water is not just corrosive to the tank / pipes / tube (I think he said "tank" but I'm including it all in case I've forgotten) in an insta-hot, it is dangerous to the drinker. (it's dangerous because what the RO water corrodes is carried through the water supply to your cup of tea) He really wanted RO water and I really wanted just one faucet. So, we're going with just one faucet that does insta-hot AND filtered water. We've decided to live with it a while and see if the filtered water is good enough. If it is, great. If it's not, then I guess we'll either have to reassess (and get another faucet) or be prepared to frequently replace the insta-hot tank. I wish I had more details for you -- when I talk with him later I'll ask to see what pertinent info I left out. I found a panoply of great-looking faucets -- Brasstech and Little Gourmet (Mountain Plumbing) both have a slew of styles and finishes. (We purchased a Little Gourmet faucet and insta-hot tank -- I think it's a Culligan filtered water system?)

First check that the drain line flow restrictor isn't plugged. It's either in line of the drain line or inside the RO end of the drain line. Second, check that the drain line is clear and is routed as straight and direct to drain as possible avoiding any up routing. Third, check the pressure in the tank and make sure you don't get any water out of the valve. Fourth, empty the tank and set the pressure at 7 psi static.

You have not stated what the symptoms are....no water to tank, no drain water, tank is full but no water to tap etc...If the RO is working you should get water from the tap. If no water but the tank is full, tank has low air. Should be 6 lbs when tank is completely empty. If water drips out of tap when open but will not fill tank then there is a lack of incoming pressure. Drain water should be a steady pencil leas size stream coming out. If it's a lot more than there is no back pressure on the membrane so the water can not be forced through the membrane. I have one years ago that debris was trapped in the auto shutoff. Discovered it by trying to hold back pressure at membrane. I could not hold back pressure at main inlet.

Full disclosure - I own a Tankless gas water heater and love it. I had a 50gal tanked gas water heater before. Due to space constraints, it could not be replaced. It was in the doorway of the utility room. Here is what I learned when looking at Tankless water heaters. Just like when you want to go solar, you have to get more efficient with your appliances. The things I did to change my plumbing fixtures were intrinsic. All these things below were done as part of replacing aging fixtures and were not related to the tankless decision but made the decision and experience with tankless flawless. Replaced all but one bathroom shower valve with a Thermostatic valve. The last one will be replaced this winter. Replace all shower heads with units that used no more than 2.5gal/min Replaced all bathroom and kitchen faucets with units that used less than 2.5gal/min My dishwashers and washers already heated their own water and all but one of my Washers can use all cold water as input. The dishwasher and washers were energy efficient and used small amounts of water. There is a large bathtub in the house and the tankless water heater is wonderful for this. We take a bath maybe twice a week. I am getting a separate temperature controller for the tub bathroom so that the filling can happen without interfering with other activities. Currently, showers take priority. My house hold has 3 adults in it and we always seem to be in the shower at the same time (3 full bathrooms). With the tankless water heater, this is no longer an issue. I like in Maryland where we get really cold in the winter:-). I have a recirculator with my tankless water heater and that is on a timer. It runs for a few hours in the morning and a few hours in the evening. When the recirculator is not running, it takes about 1minute to get hot water to the farthest location in the house. I may add the point of use tankless heater to the bathroom faucets just because it wastes time to wait for hot water. This issue with hot water at the farthest location was always a problem. I purchased the largest residential tankless water heater which with a 30degree rise, will get you 9.6gpms. This would theoretically allow me to run 3 showers and a faucet at the same time. My unit is programmed to 110F degrees and the showers are set to about 105F degrees. The thermostat for the tankless is in an easy to reach location in the hallway and I can easily increase or decrease the water temperature. I originally started at 140F which is the max temp. I changed it the first day when I could barely wash my hands without burning them. My temperature rise in the summer is about 35F degrees and 50F degrees in the winter. When I went with tankless, I had heard all the horror stories of cold water sandwiches, huge volume drops due to cold incoming water and flow rate to get started at the sink. I have not experienced any of this. I think the thermostatic valves in the shower contribute to this quite a bit. I am able to get hot water at the sink in under 10 seconds except for the farthest unit. When the recirculator is running, the water is hot within 2 seconds. Just enough time to flush the water from the steel part of the faucet. Propane would be my choice in your situation. Electric tanked or tankless water heaters would leave you in a lurch when the power went out. Propane tankless water heaters don't perform as efficiently as the natural gas units but that is true of all propane appliances. I have my tankless water heater hooked up to an uninterruptable power supply in the event of a power failure which we have quite often. I also have a small gasoline back up generator and the tankless unit works fine when connected. I have a Rinnai RUR98i. This unit has a built in recirculator pump. You can also purchase a separate recirculator with the tankless or tanked unit of your choice. I purchased it from build.com and my plumber installed it. I also installed the scale water filter before the unit and this keeps the unit operational without a lot of build up. The unit is just over a year old and I performed a maintenance in the summer. There was very little build up. I am also installing a whole house filter for sediment and chlorine due to some work the water company is doing in my neighborhood for the next year. I have not selected a solution yet for the whole house filter. Good luck with your decision.