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Old 03-12-2012, 12:22 PM   #1
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Hot Water Tank Re-Plumb

I have moved my hot water heater and am re-plumbing it. The old set-up had two problems: 1) a poorly-functioning check valve on the cold water side so when I turned on the cold water tap hot water came out for a while and 2) ultra-hot water came out of the taps after running the engine.*

Solving the second problem should be easy by placing a tempering valve on the hot water outflow. The first problem is, I suspect, from water expansion as it is being heated. If I have a well-functioning check valve, the water expansion will likely cause my overpressure valve to open, spilling very hot water into the bilge. I'm thinking of placing an expansion tank on the cold water supply side of the water heater to prevent that. I calculate the maximum expansion for the 11 gallon tank to be about a quart if heated to 180 degrees (engine temp), so can I use one of these*type of accumulator tank for my expansion tank? Any household expansion tank starts at around 2-3 gallons -- way more than I would ever need.

Thanks,

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Old 03-13-2012, 04:48 AM   #2
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Hot Water Tank Re-Plumb

Way to tiny ,and not user friendly ,, try a larger house 2 to 6 gallon unit .

*

Bigger is better for any accumulator tank , it will require less run cycles on your FW pump.

One of the few items where there is no downside to larger , except space.

Remember it must be drained down to winterize , so valve properly.

And DO follow the instructions for the internal pressure setting as that is the only way it works to max capacity.


-- Edited by FF on Tuesday 13th of March 2012 04:51:20 AM
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Old 03-13-2012, 05:57 AM   #3
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Hot Water Tank Re-Plumb

Quote:
dvd wrote:
I have moved my hot water heater and am re-plumbing it. The old set-up had two problems: 1) a poorly-functioning check valve on the cold water side so when I turned on the cold water tap hot water came out for a while and 2) ultra-hot water came out of the taps after running the engine.*

Solving the second problem should be easy by placing a tempering valve on the hot water outflow. The first problem is, I suspect, from water expansion as it is being heated. If I have a well-functioning check valve, the water expansion will likely cause my overpressure valve to open, spilling very hot water into the bilge. I'm thinking of placing an expansion tank on the cold water supply side of the water heater to prevent that. I calculate the maximum expansion for the 11 gallon tank to be about a quart if heated to 180 degrees (engine temp), so can I use one of these*type of accumulator tank for my expansion tank? Any household expansion tank starts at around 2-3 gallons -- way more than I would ever need.

Thanks,

dvd
*Used one of these in my RV and it worked great...will use one in my boat too...

http://www.homedepot.com/Plumbing-Pr...&storeId=10051

the actual size is only 8x8x13 inches

don't know anything about these but they seem to go on the hot water side..

http://www.homedepot.com/webapp/cata...&Ntpr=1&Ntpc=1


-- Edited by psneeld on Tuesday 13th of March 2012 06:00:56 AM
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Old 03-13-2012, 06:44 AM   #4
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Hot Water Tank Re-Plumb

Quote:
dvd wrote:
I have moved my hot water heater and am re-plumbing it. The old set-up had two problems: 1) a poorly-functioning check valve on the cold water side so when I turned on the cold water tap hot water came out for a while and 2) ultra-hot water came out of the taps after running the engine.*

Solving the second problem should be easy by placing a tempering valve on the hot water outflow. The first problem is, I suspect, from water expansion as it is being heated. If I have a well-functioning check valve, the water expansion will likely cause my overpressure valve to open, spilling very hot water into the bilge. I'm thinking of placing an expansion tank on the cold water supply side of the water heater to prevent that. I calculate the maximum expansion for the 11 gallon tank to be about a quart if heated to 180 degrees (engine temp), so can I use one of these*type of accumulator tank for my expansion tank? Any household expansion tank starts at around 2-3 gallons -- way more than I would ever need.

As I understand your design, the expansion tank in the cold water side will do nothing because the check valve will keep the excess volume from flowing into it.

I think you are overthinking this.* My water heater has no expansion tank and it never discharges through the TP valve.* Same for my previous boat.* Same for my home.
*(edit) OK, I examined your plan, the check valve is before the expansion tank so your plan should work.* I'm just surprised you didn't have a problem in the past without the tank.


-- Edited by rwidman on Tuesday 13th of March 2012 06:58:39 AM
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Old 03-13-2012, 09:51 AM   #5
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RE: Hot Water Tank Re-Plumb

Actually, I did have a problem in the past. Every time I turned on the cold water tap, very hot water came out for quite a while. It made it difficult to bring the water temperature down to non-scalding levels because I didn't have cold water to dilute the hot water with. This meant a considerable waste of water, draining enough for the cold water line to cool down. In the old system my poorly-functioning check valve allowed the expanded, heated water to flow backwards into the cold water line.

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Old 03-14-2012, 03:20 PM   #6
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RE: Hot Water Tank Re-Plumb

How can it flow back wards if the domestic water pump keep the lines at 30+ PSI and a check valve?*The cold water might be getting hot because is plumbed right next to the hot water.* Our cold water is warm at first as the hot and cold are next to each other.


*

*
What you want is called an Accumulator tanks which has a bladder in side which expands and it is also take the sudden PSI off the lines and reduce the number of times you domestic pump comes on.* You can buy them at Lows/home for like 75 bucks.*

*
A domestic home does not require as the water lines have a air cushion plumbed in.* If you ever have a change to look inside the wall you will see the water pipe is about a ft taller than the faucet and is cap off, so you dont get the banking of pipes caused by sudden pressure.*
*
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Old 03-14-2012, 04:50 PM   #7
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RE: Hot Water Tank Re-Plumb

Quote:
Phil Fill wrote:How can it flow back wards if the domestic water pump keep the lines at 30+ PSI and a check valve?*
He said the check valve failed.*
*
All the water in the system starts out at 30PSI (for sake of argument).* Once the water heater heats the water in the tank, the water expands and the pressure increases because there is no place for the increased volume to go.* An accumulator or bladder tank on the inlet side of the water heater but after the check valve will give this excess volume a place to go.
*
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Old 03-14-2012, 04:51 PM   #8
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RE: Hot Water Tank Re-Plumb

Quote:
Phil Fill wrote:*
What you want is called an Accumulator tanks which has a bladder in side which expands and it is also take the sudden PSI off the lines and reduce the number of times you domestic pump comes on.* You can buy them at Lows/home for like 75 bucks.*
I would chose the marine version over the residential version because it is non corrosive.* It doesn't seem to cost more.
*
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Old 03-14-2012, 04:53 PM   #9
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RE: Hot Water Tank Re-Plumb

Quote:
Phil Fill wrote:A domestic home does not require as the water lines have a air cushion plumbed in.* If you ever have a change to look inside the wall you will see the water pipe is about a ft taller than the faucet and is cap off, so you dont get the banking of pipes caused by sudden pressure.***

That might be the case and it might not.* It depends on who installed the plumbing and when.
*
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Old 03-15-2012, 05:24 AM   #10
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RE: Hot Water Tank Re-Plumb

It's not really that complicated. In my system, fresh water drawn into Shure-Flo pump - out via quite modest sized 1 litre Shure-Flo accumulator tank, then splits to hot water heat exchanger cylinder and to cold supply. No check valve - no hot water gets into the cold system. I suspect the constant pressure maintained in the line down-stream of the hot/cold divide prevents hot water back-flow.
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Old 03-24-2012, 11:03 PM   #11
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RE: Hot Water Tank Re-Plumb

http://www.pumpvendor.com/Groco_PST-1.html

I installed one of these ~ 20 yrs ago and have never looked back.* It will fill our kettle before the pump cycles again.* It will also provide protection to the system as the pressure builds from the water heating.

Using a TEE* the Pump feeds in, then the accumulator on the TEE branch, on the other side of the accumulator the line splits to the H.W. heater and to the cold side.

I used some valves and also quality brass hose connectors to separate the pump for service and allow easier drain down of the accumulator and system for winterizing.
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Old 03-25-2012, 08:15 PM   #12
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RE: Hot Water Tank Re-Plumb

Thanks, that's pretty much what I did, although it was just a standard steel 2 gallon tank special ordered through Home Depot (I looked, but didn't see what the Groco tank was made of). Also plumbed in a thermostatic valve to prevent overheated water from entering the delivery system and a valve to drain the system for winterizing. Set everything up with high-temp PVC pipe connected to PEX delivery lines. I'm pretty impressed at how easy those PEX lines were to install and connect up.

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Old 03-25-2012, 10:35 PM   #13
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RE: Hot Water Tank Re-Plumb

If you decide to use the plastic 1 liter tank you should use this one. http://www.hopkins-carter.com/ja1liacta.html*

I shouldn't say this because I sell Jabsco and Groco, but if you've got room for one of the bigger 5 gallon metal tanks, buy it at a home supply store. It will cost less than the Jabsco or Groco version. As far as I can tell, they're all just painted steel. I doubt that either Jabsco or Groco manufactures their metal tanks. They just buy them from someone who manufactures them for the home market and rebrand them.
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Old 03-26-2012, 06:22 AM   #14
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RE: Hot Water Tank Re-Plumb

Quote:
Peter B wrote:
It's not really that complicated. In my system, fresh water drawn into Shure-Flo pump - out via quite modest sized 1 litre Shure-Flo accumulator tank, then splits to hot water heat exchanger cylinder and to cold supply. No check valve - no hot water gets into the cold system. I suspect the constant pressure maintained in the line down-stream of the hot/cold divide prevents hot water back-flow.

You may find a check valve built in to the water heater inlet fitting.* Water* goes in, can't come back out.

My previous boat had that.* My current boat probably has it too, I haven't had a reason to check on it.
*
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Old 03-26-2012, 06:26 AM   #15
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RE: Hot Water Tank Re-Plumb

I would like to have an acumulator tank so the pump wouldn't run every time I draw water, but the pump installation sheet specifically states not to use one. It's a Shurflo if I remember correctly.

It's really annoying if you turn on the water just a little because the pump switches on and off rapidly.
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Old 03-26-2012, 07:40 AM   #16
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RE: Hot Water Tank Re-Plumb

Ron, that doesn't sound right. Shurflo does make pumps with variable speed motors that shouldn't have accumulator tanks but they don't turn on and off as you describe. When you turn the water on just a little, the pump will just run slowly until you turn the water off. It sounds like you have the kind that needs an accumulator tank. What is the model number of the pump?
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Old 03-31-2012, 03:05 PM   #17
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Smile

So I spent the past few days in the bilge, putting my new plumbing system together. I managed to fit the 12 Gal water heater, the expansion tank, thermostatic valve, pressure pump and filter all into one little corner. Got everything wired and plumbed -- so far so good!

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Old 03-31-2012, 03:13 PM   #18
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Greetings,
Looks pretty slick Mr. dvd but what's the purple stuff on the hosing? You must have had an Erector set as a lad.
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Old 03-31-2012, 03:55 PM   #19
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The purple pieces are hard plastic overlays that keep the PEX tubing at a 90 degree bend without having to use another fitting that would increase internal resistance. They say PEX is flexible -- yeah, like my 65 year old hamstrings are flexible!

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Old 04-02-2012, 08:00 AM   #20
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I would be wary of using PVC (or CPVC) fittings on a boat. Vibration or movement could cause them to crack or break. Flexible hoses would be my choice.
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