Water Heaters - Tankless water heaters

I own a cabin with no well. I use a 35 gallon tank in the ceiling piped to my shower and sink gravity fed. Im using the coleman hot water on demand system but the battery operated pump is too weak for a decent shower. Any ideas on getting more pressure throught the pump or is there a better tankless water system?

Can the tank be elevated?

The tank is elevated already.

installing such heaters is always a tankless job!!

sorry. couldn't resist.


How does the tank get filled? Buckets?


anyway, I looked at the thing online. I do not believe there is much you can do with what you have. You are limited by something greater than pump capacity and that is heat rise at any given GPM flow.

I do not think the unit is capable of producing enough hot water fast enough to simply pump more water through it.

Use a second insulated tank in line with the first. Be sure to elevate it as high as possible. Let the heater fill the second tank at a rate compatible with the heating of the water. When it is full use gravity to move the stored hot water to your shower.

If the problem is the unit can't heat it fast enough to pump it any faster you could install a second unit in series with the one you already have and have the first unit do half the heating and the second unit do the rest. Most tankless units should have a flow rate @ temp rise chart that would give you details as to whether a second unit would be beneficial relative to the additional cost.

The 35 gallon tank gets filled from 55 gallon tanks outside using a 120v pump. I dont think the tqnkless units will works as you need pressure to start with. Just wish I could get more pressure out of the coleman unit. Wonder if a stronger battery would help?

The 35 gallon tank gets filled from 55 gallon tanks outside using a 120v pump. I dont think the tqnkless units will works as you need pressure to start with. Just wish I could get more pressure out of the coleman unit. Wonder if a stronger battery would help?

a dc motors speed is dependent on voltage supplied so a higher voltage battery would speed things up...for awhile until the motor smoked.


how about using the 120 volt pump to pressurize the system?

Not really knowing the set up, I can think of a thousand ideas but none may be applicable to your installation.

Ill give you a visual. I have a 35 gallon sprayer tank above the ceiling in which I fill from outside 55 gallon drums with a 120v pump/ I have valves on both ends with pex goin out one side an 90 to the shower stall about 4 feet away/ the other side is pexed about 12 feet away and then 90ed to my sink. All gravity fed. Shower and sink end both have vavles so I can easily hook the coleman box up. It works fine with the pump with the extendable arm out the side for dishes but once the shower head is hooked up it just trickles out. Just need a little more pressure.

Does the unit have a rating system? Is it designed for the 3-4 GPM flow rate of shower heads? Maybe it works ok for dishes because it's designed for flow rates of like 1.5 - 2 GPM?