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Old 05-30-2017, 01:14 AM   #1
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1968 17' Caravel
Battle Ground , Washington
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How to connect PEX to original 68 water tank?

Due to a break in the copper line from freezing, I am replacing the existing mish-mash of hoses (pictured below) with PEX tubing, new valves, new sediment filter, and an accumulator tank. I am a little stumped about connecting the PEX to the fresh water tank. My original fresh water tank has a 5/8 inch outer-diameter outlet. How can I go from that to the new 1/2 inch PEX hoses.
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Old 05-30-2017, 05:31 AM   #2
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Give this a try. Easiest way I can think of.

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Old 05-30-2017, 09:03 AM   #3
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What is under the hose clamp at the tank connection? Is the tank threaded? or is that stub glued into tank? what is the stub, barbed or? Once you determine that you can better decide what is best.
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Old 05-30-2017, 09:13 AM   #4
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I had a similar struggle when I did mine. I could not find a fitting, or even series of fittings that would adapt. So I ended up building a fitting with sweated copper. I hate sweating copper and go to extreme lengths to avoid it, but that was the only option I could find.
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Old 05-30-2017, 09:25 AM   #5
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you can use std PEX to threaded adapters. Note there are four different PEX connectors sealing types. Pick one and it for all connections.
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Old 05-30-2017, 01:29 PM   #6
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Be cautious about the advice upthread. None of that will work and some of it could damage your freshwater tank's outlet barb at which point you'll be in a world of hurt.

Don't try to connect PEX directly to the tank. You'll have trouble getting it to seal and the stiffness of PEX will pose a risk of breaking off the barb as well as being noisy due to vibration from the pump.

Instead, use rubber or vinyl hose for the run from the tank to the strainer -- or part of it, at least. The existing hose in your photo is vinyl and would be a good choice. Rubber hose would seal better and be quieter but is difficult to find in drinking-water safe grades. Either way, use clamps at each end, and a hose barb where you connect to the strainer.
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Old 05-30-2017, 03:36 PM   #7
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Jammer has good advice. You want to keep some flexible hose, about 12" from the tank to PEX. Hardware store should have a poly mip to hose barb, tractor supply may as well. You can get an adapter for PEX to poly that works well going from 1/2" hose to 1/2" PEX. The regular PEX barb is too small for the hose.
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Old 05-30-2017, 03:59 PM   #8

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I found that a 1/2” threaded PVC female nipple slipped Inside the 1968GT polyethylene tank outlet barb/port/nipple with nearly no interference. Hose clamped it and built onward from the 1/2” pipe thread. Threaded on flexible tubing ASAP. Yes, the tank “barb” is extremely vulnerable to cracking, causing a world of hurt. No worry about adequate flow from tank to pump. The pump doesn't have a mile of pipe to suck through, just a few inches, and the full tank has a little “head” pressure in itself.. I have tons of water pressure and no accumulator.

Most all 1/2” gate and ball valves greatly restrict 1/2” pipe. Use lead-free “full port” ball valves where needed, avoid right-angle turns. Design with fewest fittings possible. I've never needed to drain my watertank onto the ground, so I “KISS”ed the unnecessary valve and Tee away minimizing points of potential failure. Genuine Copper PEX fits and crimps, no Sharks. In the photo, the bit of copper winding around the CAMCO tubing secures it from nipple damaging movement (ouch).

I sleeved mine internally because the tank outlet barb was cracked. I successfully polyethylene welded the barb. It repaired well, but it's a weak, cheap tank design that I cannot afford to fail.. My water tank, pump, and fittings are enveloped in shower pan lining to contain any catastrophic tank related failures. The pump isn't secured to the floor. It is on a platform suspended from above. It is remarkably quiet. Five years with no issues.

CAMCO, I believe, sells a $20 “waterpump silencing kit”, which is a couple hoses, good to design with. The way that your hose is currently attached to the tank, as jammer notes, is the smartest way. Hose clamp on a 1/2” male and attach to CAMCO kit.
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Old 05-30-2017, 06:39 PM   #9
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1968 17' Caravel
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The nipple on my water tank is not threaded. I do not object to using a flexible hose for that first part of the system, especially if it helps absorb some of the noise from the pump starting up.

I have three valves in the system, and the only one I have used is to drain the tank at winterizing time. I have already removed the city water hookup so I plan to eliminate the extra plumbing for that.


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