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 flexible lines going to an on-demand water heater
Author: roundrightfarm (WV)

Bosch recommends adding flexible lines to their AE125 on-demand electric water heater, along with isolation valves, so that the water heater is easy to disconnect from the plumbing lines for filter cleaning. What is the best way to do this?

Right now the water heater is connected with 1/2" copper on both cold water inlet and hot water outlet. Are there flexible stainless steel lines that will connect to the 3/4" male threads on the water heater and not restrict the flow any more than the 1/2" copper lines would. I don't see anything like this at Lowes.

What should I use for isolation valves? Are there smaller valves that would attach to the flexible lines and copper pipe easily and still give me good flow, or am I going to have to use a full-size ball valve and adapt to the flexible lines?


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 Re: flexible lines going to an on-demand water heater
Author: stuckinlodi (MO)

Have you checked the water lines (sometimes called "connectors") used for installing conventional water heaters? Lowe's has them. They are 3/4" size, come in flex copper and corrugated and stainless varieties, may work for what you need. I'd think you should use a full port ball valve, may need to strap the water line or valves to a mounting board for stability. The valves come in 3/4" (and 1/2") size. You can use a bushing to transition from 3/4" to 1/2" at the fittings where needed. Since your supply line is 1/2" it won't hurt to use 1/2" full port isolation valves and then a bushing to get up to the 3/4" size for connecting the flex line. You can also use 3/4" valves but you won't gain anything and they cost more than the 1/2" ones.

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 Re: flexible lines going to an on-demand water heater
Author: roundrightfarm (WV)

I never bothered to look in the water heater aisle... duh!

How should I connect the female threads of the flex line to the female threads of the ball valve? Do copper nipples exist or should I just make one? I do see galvanized nipples. Is galvanized ok for drinking water?

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 Re: flexible lines going to an on-demand water heater
Author: SHEPLMBR70 (VA)

Iso valves

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 Re: flexible lines going to an on-demand water heater
Author: stuckinlodi (MO)

Some of the flex water heater connectors come with male on one end and female on the other end so you can avoid having to use a nipple. They sometimes aren't as commonly found but my Menards and Home Depot stores have them. Or you can use a brass nipple. I haven't seen copper nipples, they would be too soft to tighten down and their threads would strip. Brass/bronze nipples work with any other metal it is connected to, that's why the metal valves are made of it. Galvanized was used for decades, it is still being used in millions of homes, it is safe for drinking water but there are better choices today. But when galvanized pipe is connected to another different metal (like copper) you get galvanic corrosion when water is present like with a water pipe. So I'd seriously avoid galvanized.

Also, a lot of folks run a short copper wire from the cold inlet to the hot inlet to help reduce possibility of galvanization caused by electrical flow thru the water heater. The wire keeps both pipes at the same small stray voltage level so no elec flows thru the water heater itself. The wire also keeps the electrical grounding intact if you have metal pipes and if the circuit breaker box has a ground wire connected to the metal water pipe, depends on the home.


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