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paulz
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# Posted: 20 Dec 2020 07:39am - Edited by: paulz
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Thinking again about adding a pressure tank to my water system.
Right now I have gravity feed from storage tank to cabin. SureFlo pump outside, Ts off direct to cold faucet one way, to L5 heater, also outside, the other. L5 to hot faucet, about 15' of 1/2 CPVC.
The pump runs every time a faucet is turned on. Be nice to fill a cup of water without, is that possible with a pressure tank?
Other issue is the amount of wasted water waiting to get hot water through the pipe to the faucet. I assume the tank would go directly after the pump, before the heater, so that would not change, right?
What size and type of tank should I consider?
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FishHog
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# Posted: 20 Dec 2020 08:40am
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your pump maintains a certain pressure in your system say 40-50psi. A tank will then be at that pressure, you will be able to get some water out of it before the pressure in your system goes below the 40psi and kicks back on. Problem is you can't know when that is. If your tank is sitting at 41psi before you want that cup of water, it will drop below and the pump will kick on anyway.
And your right there will still be a delay to get hot water.
Those are two of the disadvantages of these pumps and on demand water heaters. I think you will be disappointed with the minor improvement a pressure tank will make. Its just one of those things that I think you need to live with in these types of systems.
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Steve_S
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# Posted: 20 Dec 2020 09:14am
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I have a 50 Gallon Pressure Tank in Pumphouse, deep well pump, 260' below it. (Grundfos SQ5 soft start 120V). It kicks on at 37psi off at 49PSI starts at 500W and stages up to 1100W by the time max pressure is reached. Water then goes through a Sediment Filter then a Fine Filter (Rainfresh systems), I only lose about 2PSI.
On-Demand Hot Water heater is an EcoTemp FVI-12-LPG and it does not have any issues at all when pressure charge... In fact, you can be in the shower, nice & really hot and you never notice the change in pressure.
There is a GOTCHA !
If you empty the pressure tank which will be warmer than the fresh cold water coming out of the ground, your water heater will have to work a little harder to make up for the temp difference. That may reduce the pressure slightly on the Hot Water side.
It's not usually for folks up here to install a "Pre-Mix" blender Valve that chases a trickle of hot back into the incoming cold line for pre-warming. This is similar to a Post Mix Balancing valve but NOT the same. Not easy to find but they are out there.
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ICC
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# Posted: 20 Dec 2020 09:50am
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Quoting: paulz Be nice to fill a cup of water without, is that possible with a pressure tank?
I am curious. Why would it be nice?
I look at it from a different point of view. If you hear the pump run in short bursts when nobody is drawing water you know there is a leak or a valve not closed properly.
As for wasting the water as you wait for the heated water to arrive at the point of use, borrow and modify an idea from what is available for systems that use a water heater storage tank. There are systems made that have a pump and a return line from point of use back to the water tank. The pump runs and moves water from the heated water tank, through the hot pipe to the point of use where a special diverter valve sends the water back to the water heater tank. When the water is warm enough that special thermostatically controlled valve closes. Then when the hot faucet is opened there is warm or hot water right there almost instantly.
For a plumbing system with an on-demand heater this idea can be applied IF there is a cold water storage tank that the water can be returned to.
I have used a method that works in my RV for decades. In the RV it is simple because every one has a fresh water storage tank. This only works when using water from a storage tank, not when water is coming from the shore connection. Similarly with a house or cabin this won't work if water is coming directly from a well, with no intermediate storage tank.
Run a return line from the faucet area back to he storage tank. Insert a tee fitting as close to the faucet hot connection as possible. The return line is connected to the tee. At a convenient point a valve (ball valve is best) is placed and that return line is routed through that valve. When hot water is wanted the diverter valve is opened and water runs from the heater back to the cold water storage tank. You will need to figure out how long it takes for the water to be hot at point of use.
I used a quarter turn supply line valve placed in the base cabinet face frame. The valves feels warm as the hot water arrives. Turn that valve off and then hot water will be at the valve within a second. No water is wasted.
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paulz
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# Posted: 20 Dec 2020 10:17am
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Quoting: ICC I am curious. Why would it be nice?
For example, I run water for a second on my toothbrush. Add paste, brush. Run water again to rinse and store brush. Run water again to rinse. Or get hands wet, soap down, rinse, soap again..
Maybe the pump is good for a million cycles, just feels like I'm wasting it.
For the hot water issue, my bathroom is already sheetrocked and painted (only place in the whole cabin..), not worth tearing into. Something that plumbed in right under the sink, electric or gas, would be good...
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ICC
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# Posted: 20 Dec 2020 11:04am - Edited by: ICC
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Quoting: paulz Maybe the pump is good for a million cycles, just feels like I'm wasting it.
I have been using the same Shurflo pump in my RV since 2000 when I got it second hand. Chances are it is the original factory pump from 1992. If so, it is 28 years old. No idea how many thousands of times that pump has cycled but the RV has 200,000 miles on it.
Those pumps can run dry indefinitely with no harm. No gear wheels, no lubrication needed. I have a pre-pump filter to ensure there is no debris, no dirt particles that can cause issues with the diaphram valves. Most problems stem from dirt or poor winterization and freezing.
Look at the Watts recirculating pumps. Maybe you can use their principle..... They are designed for use with storage hot water tanks installations where there is a long run from heater tank to a bathroom or whatever at the other end of the house. Here in the SW desert where water is costly they are popular for locations that cannot easily convert from a storage tank to an on demand system. They use the cold water line to return water to the heated water storage tank. The diverter valve is available as a replacement part. They are not designed for an ondemand system but a person could come up with something that would eliminate that waste of water.
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paulz
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# Posted: 21 Dec 2020 08:53am
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Thanks ICC. So if I understand it correctly, when the hot water in the line cools off, the pump runs to put hot water back in, pushing the cold water back. I guess the times the pump turns on depends on how long it takes for the water to cool off. Could the existing Sureflo pump be used with the proper valving?
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ICC
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# Posted: 21 Dec 2020 11:18am
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Quoting: paulz So if I understand it correctly, when the hot water in the line cools off, the pump runs to put hot water back in, pushing the cold water back.
No. The watts pump has an integral timer. Just a simple syncronous motor timer. The on and off times are selected and the pump runs when set, like in the morning when you usually get up, or the evening when you take a shower. Owners choice. Everyone who has one on there water heater tank system loves them. I had one in the old house; new house does not need one.
The thermostatic valve closes the return path. So when the water gets warm at that valve it blocks the water flow. The type of pump used can not be hurt when the flow is stopped like that. But the pump contnues to run which when on grid power is no big deal.
I have seen others wire in a switch at the point of use. That way they just push a button and the pump runs and soon they have warm water without wasting water down the drain. But that needs the extra wiring, etc.
The trick to solving the water waste is to devise a way to cycle the water flow from the water heater tank back to a storage space instead of running it down the drain. In the RV that was relatively easy when I was remodeling it. Some friends have done the same in their off grid, no well, cabins. Easier done when building but if water conservation is important one has to devise a suitable method to pipe the water back to storage.
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paulz
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# Posted: 22 Dec 2020 07:55pm
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OK I get it, thanks ICC. Since we're on cabin time, not sure my schedule is steady enough for a timer.
I did some measuring today. It takes about 15 seconds, 1 quart of water, to get lukewarm. Hot after another 15 seconds and quart, roughly.
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FishHog
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# Posted: 22 Dec 2020 09:09pm
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When I built my camper, I put a 3 way valve at my shower head. One of the ones you have in a shower to change to a hand wand from the shower head.
I plumbed it back to my water tank. I run the water through that loop until I can feel hot water at the shower head then turn the valve and shower. Works great to save water there where I only have a 20gal tank.
I thought of doing the same at the cabin, but the 1/2 gal of water it wastes just wasn't worth the extra plumbing when I have a 250gal tank and its not hard to refill.
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paulz
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# Posted: 23 Dec 2020 10:07am
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That's a great water saving solution Fish, but like you I have abundant water at the cabin. It's more the waiting.
I noticed they have small point of use electric water heaters. Haven't fully investigated, here's one brand. It would seem that a well insulated unit of a gallon or less wouldn't take much to run, and would keep the water hot for hours. Don't see why it couldn't just be plumbed in the hot water line under the sink. For the shower I can wait.
https://gadgetsgo.com/Waiwela-WM-1.0-pou-point-of-use-booster-heaters.html
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