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Old 18-10-2015, 07:51   #1
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Replacing Hot Water Lines

I had a hot water fitting crack going to the head sink. The fitting is grey plastic and connects to 1/2" flexible grey plastic tubing. I was able to use a 1/2" hose clamped over the grey tubing to temporarily restore water to the galley sink. However, I am concerned about the other old fittings and tubing which date from original construction in 1987.

The home PEX tubing (Home Depot, Lowes) would appear to be appropriate for the cold water side but I am especially concerned about +180 degF hot water coming from the water heater.

Should I use Seatech series 35 fittings and are there other options I should consider?
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Old 18-10-2015, 08:26   #2
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Re: replacing hot water lines

It sounds like you have older Qest plumbing, and this is known to fail over time. We have Qest fittings, but PEX tubing, and the fittings started occasionally failing after 15yrs. I believe the Qest tubing has a worse reputation than the fittings.

There is no issue with using PEX tubing for hot water. It is widely used throughout homes, RV's and boats in this application. And it is inexpensive. Frankly, I don't understand why people still plumb boats with vinyl hose.

Don't worry about the color - red, blue, white is just for keeping track of what lines are what. They are all the same physically. You can use any of several types of fittings for this - sharkbite, crimp bands, etc. No need for the very expensive marine brands like whale, etc. You can even reuse your old Qest fittings, or get new Qest ones (the new ones are a different plastic formula which don't have the older issues).

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Old 18-10-2015, 09:52   #3
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Re: replacing hot water lines

Thank you for the quick response. I have used the conventional PEX connectors and tubing (from Home Depot) for our watermaker. I was hoping I could use the same system and remaining supplies for the cold water side. It sounds like you think those on the hot water side as well.

We have a 6 gal Raritan, with 3/4" (NPS or NPT?) threaded fitting. Since that is the hottest point in the system, what is advisable to connect directly to that 3/4" fitting, a standard PEX connector from Home Depot, something like a Seatech series 35 fitting and PEX or perhaps a brass hose barb with a series 135 hose for the 2-3 feet closest to the water heater?
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Old 18-10-2015, 11:44   #4
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Re: replacing hot water lines

The PEX to our water heater is directly connected with common grey Qest fittings. No problem in 17yrs. There are copper PEX connectors if you are concerned about that.

You really seem to be looking for a reason to spend more money on those Seatech fittings!

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Old 18-10-2015, 12:44   #5
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Re: replacing hot water lines

Quote:
Originally Posted by colemj View Post
The PEX to our water heater is directly connected with common grey Qest fittings. No problem in 17yrs. ....
Same here for 15 years.
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Old 18-10-2015, 14:52   #6
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Re: replacing hot water lines

Sure don't need to be spending more money. I think I will just replace the series of tees at the end of the Qest tubing with PEX. Thanks again.
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Old 19-10-2015, 04:56   #7
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Re: replacing hot water lines

“Uponor” (brand) PEX (all colours) carries the following hydrostatic temperature and pressure ratings:
• 200°F at 80 psi (93.3°C at 5.51 bar)
• 180°F at 100 psi (82.2°C at 6.89 bar)
• 120°F at 130 psi (49°C at 9 bar) (½" Uponor AquaPEX® tubing only)
• 73.4°F at 160 psi (23°C at 11 bar)
However, some plumbing codes do not allow for PEX to be used within 18 inches of the water heater (use a steel/copper nipple).

Most boats operate at a water pressure of 30 to 50 PSI (max).
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Old 19-10-2015, 06:59   #8
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Re: replacing hot water lines

A least one other advantage of Pex is that it doesn't burst when frozen.
I re-plumbed my house twenty or so years ago with Pex, and it has worked well.
I like vinyl in the boats because it flexes so easy, but I am sure Pex is a better water pipe.
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Old 19-10-2015, 07:00   #9
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Re: replacing hot water lines

PEX for sure. I switched last year replacing all my copper which had become brittle and after a freeze many bursts. PEX doesn't have that problem. Color coding is a plus as well. It was easy to run and we did the whole boat in four hours!
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Old 19-10-2015, 08:17   #10
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Re: replacing hot water lines

Can I use the PEX connectors and hose at Home Depot/Lowe's or should I use something like the Seatech brand connectors and hose? What about a check valve on the intake side at the pump? I have heard the shuffle check valves are prone to failure. Currently I have a 1/2" hose connecting the Shuffle freshwater pump to the 1/2" grey water line to the water heater and grey plastic 3/4" fitting on the water heater freshwater ports.
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Old 19-10-2015, 08:52   #11
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Re: replacing hot water lines

Quote:
Originally Posted by dknowland View Post
Can I use the PEX connectors and hose at Home Depot/Lowe's or should I use something like the Seatech brand connectors and hose? What about a check valve on the intake side at the pump? I have heard the shuffle check valves are prone to failure. Currently I have a 1/2" hose connecting the Shuffle freshwater pump to the 1/2" grey water line to the water heater and grey plastic 3/4" fitting on the water heater freshwater ports.
I did
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Old 19-10-2015, 09:33   #12
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Re: replacing hot water lines

Only Pex connectors I have used had a ring that was compressed with an expensive compressor and it is pretty large and may not fit well in a boat.

Can you use "shark bite" connectors with Pex?
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Old 19-10-2015, 09:46   #13
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Re: Replacing Hot Water Lines

Yes, shark bites or equivalent work.
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Old 19-10-2015, 09:56   #14
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Re: replacing hot water lines

Quote:
Originally Posted by dknowland View Post
Thank you for the quick response. I have used the conventional PEX connectors and tubing (from Home Depot) for our watermaker. I was hoping I could use the same system and remaining supplies for the cold water side. It sounds like you think those on the hot water side as well.

We have a 6 gal Raritan, with 3/4" (NPS or NPT?) threaded fitting. Since that is the hottest point in the system, what is advisable to connect directly to that 3/4" fitting, a standard PEX connector from Home Depot, something like a Seatech series 35 fitting and PEX or perhaps a brass hose barb with a series 135 hose for the 2-3 feet closest to the water heater?

Just finishing refurbishing our 6gal. Raritan (3/4"npt) connected to Qest fittings and piping (original). Sacrificial anode was long gone resulting in corrosion causing damage. Corroded steel nipple exiting heater split the Qest connector in addition to corrosion in other areas. Anode looks like a nipple should be on the hot side in this case was on the cold, likely because of access. At $1250+ for one of these Raritans no small deal so just thought a heads up might be of some benefit here.
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Old 19-10-2015, 09:57   #15
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Re: Replacing Hot Water Lines

I'm easily impressed I know, but shark bites are pure magic, nothing could be easier.
If you can use Pex with them, then I know when I re-plumb what I'll use.
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