We purchased a used 1996 Jayco Sportster 8. It had only your typical cold water with pump style sink faucet. DW will no longer camp with out hot water (whole group got sick once due to improper cleaning).
Being a small camper, there really wasn't room for a regular rv tank hot water heater, so I decided to try one of the tankless water heaters.
It helped that on our camper, the back of the pop-up is a metal coated board, not canvas.
I mounted the heater on the back of the camper, installed plumbing for hot water lines, and a shurflo pump, and a regular sink faucet.
Well, tonight we put water into the TC and after fixing 2 small leaks, we turned on the hot water faucet and instantly the heater kicked on (it is water flow controlled) and moments later we had hot water flowing from the sink and outside shower set up I had installed.
24'Class C TIoga Montera
1996 Jayco pop-up TC
OK, here are some of the specifics. We ordered the heater from the manufacturer EZ Tankless
http://www.eztankless.com/index.php/products/tankless-water-heaters/ez101-outdoor/ for $134.95 free shipping.
I fabed up the ring holder that holds the chimney to the top out of some aluminum and a stainless u-bolt. The chimney is a double walled 4" pipe 36" long with a top cap. It will travel inside the camper and be placed through the top loop before se raise the top. It "just" fits inside and allows the top to raise as it slides in the loop.
The tank runs on 2 "c" cell batteries and kicks on when it senses water flow, kicks off when flow stops. Works a lot like the Shurflo pump.
Make sure that you put a one way check valve on the outlet of the sureflow pump. If you don't it could over pressurize the internal valves or rubber piston in the pump and blow it out. Ask me how I know! lol. I blew two of them up good.
Better yet you might want to put a pressure regulator on the outlet side of the pump that returns to the inlet side to keep the whole system from over pressurizing. the equipment I put a similar system on was a carpet cleaning machine and put let pressure was not an issue.
The EZ101 has a pit-cock to drain water from the coils. As you can just see at the bottom of the picture, I also added valves to the water pipes below the tank so that when I winterize I can open them and drain the water there also.
As for the pump, I did install a check valve right after the pump to prevent city water pressure from affecting the pump.
It was great last night after I fixed my 2 small leaks to be able to add water to the tank, then on 12 volts to be able to turn on the pump switch and when I open the faucet to first hear the pump kick on and moments later to hear the water heater light off and to feel hot water start to flow from the faucet. VICTORY!!
How many "moments later?" I ask because you have a limited amount of water in the fresh tank and it takes some water to make the tank start heating, and it takes some more to move the hot water to the faucet.
With a normal suburban water heater setup, the water is in the tank already and none is wasted making the heater kick on. The heater and sink are typically very close together so only a tiny amount of water is wasted getting hot to the sink.
Well, I'll tell you in our class c Tioga, the hw tank is on the street side under the dinette seat, while the sink is on the curb side a few feet back. In it we used probably a quart or more before the hot water arrived at the sink.
In the TC, it was more like 1/2 pint, Now, I am talking about after the first light off. That took some time to light off and I think probably just because gas hadn't been put to it yet at that point. After the first light off, every other was on almost instant light off as soon as we opened the faucet, and the hot water arrived very quickly arrived after that.
I think that part of the speed may be due to my putting in the check valve right after the pump (don't think the Tioga has one) so there is water pressure in the lines right from the very start. Not sure but it is a lot faster than in the mh.
I have a similar set up, I mounted the hot water heater to an aluminum 2 wheel dolley. Put the 20lb tank on the bottom foot of the dolley. And mounted a 12volt pump to the dolley. So I can take it anywhere.
But be aware, it never completely drains the water out. So DONT LET IT FREEZE!! My first one did, and leaked bad.