Dielectric union at pressure tank or not ?

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petepdx

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I'm rebuilding a wells plumbing.

The pressure tanks fitting is a galvanized 1-1/4" FPT.

The cast brass tank tee I've selected with a union, is 1-1/4" MPT to the tank.

Should I be concerned about corrosion ?

If so, I can't find a dielectric union of the right combination.

The best I could come up with is a union with copper SWT to galvanized FPT, then one would need a galvanized nipple, a short section of 1-1/4" copper; and a 1-1/4" copper SWT to FPT.
 

Reach4

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Not a pro... If this is for indoor use, I would use PVC if it is permitted. That will provide the electrical insulation (dielectric) plus it is easy to work with.

I would be concerned with corrosion. Using the insulating pipe to transition will minimize the corrosion of steel even better than a dielectric nipple or union..

I know some codes do not permit PVC but will permit CPVC. Yet PVC is often used in wells. So where do they draw the line as to where the PVC is permitted on the well water and where PVC is not permitted? I don't know. My well water comes in in polyethylene. Then it goes to PVC past the pressure tank. A few feet later it transitions to copper.
 

petepdx

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The install I'm doing is to last about a year, then the whole system will be replaced. It is inside. The well's pipe is galvanized transitions to PE then the old setup the PE went to galvanized pipe and fittings, the old tank tee is brass with no dielectric union. The iron removal setup has a brass air injector that is threaded to galvanized. Eventually gets into the house with galvanized. All the old galvanized which is 50 years old is clogged. I too have considered a PVC union, but since the union would be under the tank, it would be a bitch to service. All the other fitting will be easily accessible.
 

LLigetfa

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I find that lathering pipe dope on the threads is enough to allay concerns of dissimilar metals. I would never use PVC where brass fittings are available at reasonable cost.

Most tanks have steel threads and brass tank Tees are very common. I would think that if it were an issue, that retailers would try to sell you a dielectric union with every tank they sell.
 

Craigpump

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Use a brass T and fittings, screw the T into the tank and forget it for 20 years.

I'm with LL, I'd never use a PVC tank T.
 

Reach4

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He already has a cast brass tank tee. He has a female steel FIP on the tank, if I understood correctly.

Would you never connect from a tank tee to a pressure tank with PVC?
 

Craigpump

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Nope

PVC tank T's look like they're from freaking Homeless Depot, Blowes or Tractor Supply and we don't want our work to look like DIY.
 

Reach4

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Nope

PVC tank T's look like they're from freaking Homeless Depot, Blowes or Tractor Supply and we don't want our work to look like DIY.
Only you have mentioned PVC tank tees.
 

LLigetfa

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Why use PVC at all when the brass Tee screws directly to the tank? Make no sense at all to add a weak point. PVC male thread ends are OK since they have good enough compressive strength, but PVC female threads are a catastrophe in the waiting.

Dielectric unions are only needed between steel and copper. AFAIK, plumbing codes allow for a 6" brass nipple to be use in place of a dielectric union.
 

Craigpump

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I don't recall saying anything positive about PVC tank tees. I don't like Flex lite tanks because of the PVC nipple, but sometimes we have to use them in damp, wet conditions.
 

hj

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Brass tank to to galvanized piping does NOT need a dielectric union, (the unions are "for looks" anyway and do not do what they are supposed to do). I do not know of any code that permits PVC INSIDE a building, nor would any competent plumber ever install it even if it were permitted. I value my liability insurance premiums to much to risk it.
 

Craigpump

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I don't know if code allows it, but we see PVC used for interior offsets and for tank T's at least a dozen times a year.

I know that doesn't make it right, but inspectors pass it.....

What's the difference between PVC & CPVC?
 

Reach4

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I don't know if code allows it, but we see PVC used for interior offsets and for tank T's at least a dozen times a year.

I know that doesn't make it right, but inspectors pass it.....

What's the difference between PVC & CPVC?

A non-code real difference: PVC deteriorates over time with hot water. It is more rigid than CPVC. CPVC of the same nominal size is normally smaller than PVC. From a logic point of view, the piping to a well pressure tank would never be hot water.

From a code point of view, CPVC is allowed many places, and, as hj said, PVC is not allowed inside for pressurized potable water under newer codes-- unless an exception for wells exists, and nobody has identified such an exception I guess. My well water to the pressure tank is piped in PVC, and I am not worried about that. I thought maybe piping of well water to the pressure tank would be a special case up to a point. That is clearly not going to ever be even warm water.

I put a high clearance nickle plated ball valve on a nipple, instead of the plastic drain valve , on my water heater. This was to make flushing more effective (and I got what I thought to be an incredible amount of stuff flushed out). I used a schedule 80 CPVC nipple for the job. Normally CPVC is copper pipe sized but this nipple was iron pipe sized with 3/4 NPT threads. I could have gotten by with galvanized or brass, but I was cautious. I had used a 3.5 inch galvanized nipple when I replaced my tub diverter. Brass was not readily available in that size where I was shopping. I was amazed at the dose of rusty water that came out when I turned on the faucet after it sat for a couple of days. I replaced that nipple with a brass nipple, and no rust. Oddly one end of the nipple was screwed into existing galvanized. I think that galvanized had acquired a patina (probably from before the softener was put in) and was not putting out rust. I am probably overly concerned about a little rust. In the case of the water heater, I wanted to avoid corrosion where I could. I have put in effective filtering, so the water heater should not pick up any new sediment.
 
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