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on-demand water heaters
#1
We've had this propane water heater for about 5 years, and I haven't had a decent shower in all that time.

The hot cuts in and out as the water pressure goes up and down. I'm on catchment, so have a pump and pressure tank.

Is there a trick to this?

I'm about ready to go back to electric hot water--is $40 a month too much to pay for decent showers?
...and hot water for washing dishes
...and not having to haul propane tanks

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#2
I believe this has all been discussed before.

I get reliable service from a DC water pump (2.9gpm, 30psi) through a 5L heater. If the pressure/flow is otherwise adequate, a regulator might fix the problem by preventing sudden pressure drops through the heater.

is $40 a month too much to pay

Depends how much the propane costs. Electric on-demand heaters exist; for standing tank, there's always adding a solar collector to offset the power consumption...
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#3
thanks.
pretty much everything has been discussed at some time, but finding it is difficult. A search for "water heater" returned 18 pages of posts, most with only glancing mention of water heaters.

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#4
Try a search for "eccotemp" or maybe "takagi".
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#5
Lee, I don't know if you are off grid or not but I've not had one problem in 10 years with the system I have. I'm running a Grundfos tank less pump with a Takagi jr. on demand water heater. I have installed this same setup in for 3 other people and have had no issues.. My water runs at a constant pressure and even temperature, even when both showers going at the same time. Only time there is an issue is when I forget to change the filters!! Wink No the system isn't cheap but it works me. If you are running a UV system, you can get a shot of very warm water if the water hasn't been turned on for several hours... The water in the UV tank can get up to about 130*.....




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#6
When we got our solar hot water system the cost was about $5000ish however after rebates and tax credits the net cost was about $1700. We've had it long enough that we are past the pay back time so now all our hot water is effectively free. Drainpipe can give you a free estimate including what your estimated net cost will be after available rebates and credits. We love our solar hot water system. After Iselle the free hot water was nice because the generator we had at the time wasn't able to be hooked up to a 220v circuit.
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#7
Terracore, what kind of pump do you have?
Lee, your shower head probably restricts water flow below the threashold you heater starts to warm water. Remove the restrictor and you should be good to go. You'd think these heaters would have a lower volume set point to work better with these f****n low flow devices that the EPA is forcing on us.
Puna: Our roosters crow first
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#8
First, tank-less water heaters have been somewhat over-hyped as though they have no flaws and are the answer to every conceivable problem. They have their place but they also have drawbacks. They must modulate the gas flow to match fluctuations in the water flow rate if a stable temperature is to be maintained. It is a fact of life that that is an imperfect process, more so on the less expensive models. They all seem to have the feature that if the flow and/or pressure drop too low the gas gets cut off, probably both to keep from producing slugs of scalding water and to keep from burning up the heater. I had no problems until I had a lot of company during the spring when the algae was blooming. The resultant loading up of my filter cut the flow rate of water and suddenly I was getting complaints that the water was too hot until it suddenly got cold. The solution was to clean my filter to get more flow. Actually in my case I have made several upgrades that go beyond solving the immediate problem. Some may recall that I have the Sawyer PointONE filter. It filters out anything larger than 0.1 microns. It was hugely expensive but will pay for itself over the long haul as it requires no energy (apart from pumping costs to force water through under pressure) and it is supposed to last 10 years. No annual cost for a UV bulb either. Naturally the stuff it filters out accumulates on the inlet side of the filter and must be removed periodically by backflushing. I had not done this for months and frankly I wonder that I did not have problems sooner.

A typical shower head flows around 1.5 gpm to 2.5 gpm. For the sake of argument lets say my shower head flow rate was around 2 gpm. My single Shurflo 4008-101-E65 pump claims to put out 3 gpm. It also claims to put out 55 psi. My experience with the pump confirms both figures, just not at the same time. As I troubleshot the problem I saw that while the pump was pushing water into the inlet of the filter at close to 55 psi, the pressure at the shower head was barely more than 20 psi. That's more than 30 psi drop across the filter and with only 20 psi at the shower head I was probably getting less than 1.5 gpm flow. My next step was to double up on the pumps, running 2 pumps in parallel. Come to think of it the figures above may have been with the second pump already in place. The pumps acted weird together so I controlled both pumps off of the same switch. They behaved better then but made a lot of noise as the pump pulses interacted. I kept turning up the pressure controls on the pumps until they finally would not shut off. Couldn't figure that one out until I went into the bathroom and discovered that the pressure relief valve on the water heater was relieving pressure all over the floor.

That whopping pressure drop across the filter was really kicking my okole. The filter manufacturer claimed that gravity flow of only 5 ft of head would result in nearly 20 gallons per hour, much less than what was required for a shower but if I piped that to a clean-water tank I could pump from that tank without the restriction of the filter at all. The clean-water tank would re-fill overnight using only gravity and hence no energy. This would be a vast improvement over a pump struggling to put out 55 psi but only getting 20 psi results at the shower head.

Long story short that's what I did and it seems to work pretty well. There were setbacks such as the hours I spent staring at the pathetic trickle of water coming out of the filter despite 6' of water in the tank, repeatedly flushing the filter to no avail. Only when I attached a hose to the filter outlet and saw that the trickle not only slowed but reversed as I lifted the end only half way up the tank did the gurgling noise coming from the pipe leading from the tank make sense. I had lost prime and the estimated 1 gph flow rate was due to having only inches, not feet of head to push the water through. I fixed that problem and now I am getting close to 20 gph when the catchment tank is full and the clean-water tank is low. As they equalize the flow rate decreases but as that means there is more water in the clean-water tank that is OK.

I should also say that I bought a new Dankoff model 2910-48 rotary vane pump that operates directly off my 48 volt battery bank. While the old Shurflo pump experienced a huge decrease in flow rate as the pressure built up the Dankoff 2910 just slows down slightly, never straying far from 4 gpm. Even sucking water through a 5 micron filter and feeding water to the shower head at a true 50 psi the new pump more than keeps up with the shower and shuts off periodically.
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#9
From the Eccotemp website:
***Please keep in mind that the L5/L7/L10 is NOT to be permanently mounted or left unattended as it is not recommended and can be considered a hazard. Not for indoor usage or to be vented. Also, these units are not to be plumbed in to the side or any other part of the house or location and is meant to serve for recreational use only. Using in the manners stated will violate your warranty.***

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#10
From the Eccotemp website ... will violate your warranty.

Good one -- thanks for the laughs!
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