Two Pressure tanks, two locations, one pump, one controller

[The Todd Man]

Hi everyone, new to the forum but not to plumbing...lol. I have just installed a much-needed new system w/ pressure tank, hot water heater and softener in a new addition in our home.

The previous owner ran about 70' of 1/2 inch copper (hot and cold) as the original water supply, including about a 15' rise in the run. Needless to say, the pressure was ridiculous as was the time to wait for hot water.

The new system is great, but I need to tweak it. I had to use a section of the original 1/2 pipe run (about 10', including 4' vertical rise) because it went underground between the two buildings and was heated. Big job to remove it.

So, I used both pipes to feed the new pressure tank using a "Y" configuration at each end, connecting to a 1" poly main feed. Incoming supply is 1" poly teed at the original pressure tank (output side).

This is the only bottle neck in the run with respect to resistance.

Since I'm using only the one pressure switch to call on the pump, I'm not sure what PSI I should set the new tank bladder to.

Right now, I'm running 40/60 on the original tank with a higher cutoff setting @ 63 PSI to maintain a higher pressure on the new pressure tank downstream. Bladder is charged @ 38 PSI.

I'm getting (roughly) 20/50 at the new tank, so that's where I need to tweak the system. Bladder is charged @ 36 PSI (I guessed that it should be lower?).

Your input would be greatly appreciated !

Regards,

Todd

 

[Bannerman]

Unless there is a pressure regulating device located between each tank, there should be no pressure discrepancy between the two tanks. If the pressure gauge for each tank is not reading identically when there is no water use, then I suspect there is a defect with one or both gauges.

Why are the two pressure tanks located in different areas of the home?

 

[Sponsor]

 

[Reach4]

Since I'm using only the one pressure switch to call on the pump, I'm not sure what PSI I should set the new tank bladder to.

With a submersible pump, set the pressure tank that is at the pressure switch to two PSI below the cut-on pressure. If you experience a pressure stutter when the pump turns on, lower it a tad.

For the one in the other building, I would guess 2 psi below the lowest pressure that you see on that tank. Usually you don't want to have a pressure tank in the other building -- especially a large one. There can be interactions.

Air precharge is set with the pressure near zero. However it can be useful to look at the air pressure while there is water pressure to compare calibration for the air pressure gauge and the water pressure gauge. They should be close in pressure, and difference more than about 1 psi would be due to the differences in the gauges.

 

[The Todd Man]

Thanks for your input, guys!

Bannerman - to answer your question - in doing research locally and on-line, I couldn't get a straight answer from anyone to install a new pressure tank or not. One guy (an experienced local) suggested I tee the line before the existing pressure tank and the have the new tank's pressure switch call on the pump that way......but I had no idea how to wire it.

The only benefit I could determine was less cycling. Not knowing the age of the submersible pump, I erred on the side of caution with the thinking a rest for it could do no harm. The tank and fittings were a little over $100 bucks....so I figured, why not? Hoping this doesn't create a problem/conflict in the system?

Both pressure gauges on the tanks are new, but I won't rule out a defect either having gone through many over the years. Thanks for the heads up.

Reach4 - thank you for your input. I'm going to move forward with testing and I'll share my findings.

Thanks again!

Todd

 

[Bannerman]

I had interpreted your original post to indicate the two tanks are not located beside each other, but the new tank is located in the new area of the home with a considerable distance between the two tanks.

Both tanks should be reading the same pressure and have the exact same air pre-charge.

A pressure tank's purpose is to reduce short cycling by the pump. The presssure tank is to be large enough so that raising the system pressure from 40 psi to 60 psi will require the pump to run for 60 seconds or longer. Adding a second pressure tank will increase the minimum pump run time as the two tanks are equivalent to one tank with the same capacity of the two smaller tanks.

 

[Reach4]

Both tanks should be reading the same pressure and have the exact same air pre-charge.

Plus altitude compensation. Instead of measuring the altitude and computing, watching the gauge bottom seems to me to be the better empirical method.

 

[The Todd Man]

Thanks again, guys!

To be clear, the new tank is located in the new area of the home with a considerable distance between the two tanks (50 feet).

I now have discovered an air-lock in the copper piping and some very funky plumbing work. I think buddy may have been drinking on the job, lol.

No cold at the toilet and only hot at the tub/shower - but have hot and cold water downstream (end of the run) at the sink. All valves functioning properly.

Just replaced the cartridge in the shower faucet a couple of months ago, so it's not that. Now running direct PEX to all fixtures out of the manifold (easy).

"Hmmmm....hope I've got enough sweats and couplers...."

LOL!

Will check readings after I deal with the air lock.

Todd

 

[Reach4]

I now have discovered an air-lock in the copper piping and some very funky plumbing work. I think buddy may have been drinking on the job, lol.

Air lock in pressurized piping is a myth.

If you get air in your pipes, it blows out. Done.

 

[Bannerman]

What is the purpose in locating the 2nd pressure tank so far from the 1st tank?

You said the pump's pressure switch is adjusted for 40/63 psi. This means when the pump shuts-off, the system pressure throughout the house will be 63 psi including at the 2nd pressure tank. The only system pressure variance will be due to an elevation change so if the pressure switch is located in the basement, there will be 1 psi pressure decrease experienced for every 2.3' of vertical pipe rise.

Even with the two tanks being located 50' apart, if they are mounted at the same elevation, the pressure will be equal in both tanks when no water is being consumed.

 

[Reach4]

Even with them being located 50' apart, if they are mounted at the same elevation, the pressure will be equal in both tanks when no water is being consumed.

And if they are at 15 ft difference in altitude, the difference in psi is about 6.5 psi.

Measuring psi differences is often easier for people than measuring altitude differences.

I guess another procedure would be to measure the no-flow pressure difference, and adjust the remote precharge to 38 plus the appropriately signed difference.

 

[Boycedrilling]

Air lock in pressurized piping is a myth.

If you get air in your pipes, it blows out. Done.

Sorry, but you're just plain wrong.

 

[Valveman]

With any distance between the two tanks and any restriction, there will also be friction loss. The tank that is closer to the pump will fill up first, the pump will shut off, then the first tank will drain into the second tank until the pressure equalizes, except for elevation differences. It is usually better to just put both tanks at the pressure switch location.

However, if you have a Cycle Stop Valve, both tanks will fill at 1 GPM. At 1 GPM flow there is no friction loss, even in restricted pipe, so both tanks, even in different locations, fill at the same rate. But if you had a Cycle Stop Valve you certainly wouldn't need the second tank. You wouldn't even need a very large primary tank.

Although, the CSV will still work with the two tanks, and eliminate the friction loss problem I was talking about.

 

[The Todd Man]

Hi guys,

Wow. Talk about great information. Thank you all so much for your input....it is greatly appreciated.

It's beer o'clock after dealing with probably the worst copper plumbing job I've ever seen in my life....and I've seen stuff a crack addict did on my old house.....so this was really bad.

There was an air lock. No question. There was no sweating on the pipe leading up to the valve (crazy humid today). Buddy did a funky 6" 45 run in front of two 90's. Don't get me started. Overall, I took out a dozen 90's and four tees for a simple 4 piece bathroom feed. Needless, awful work.

Pretty sure I bought 5 PSI on resistance alone running direct PEX.....feels like it. I've never seen the toilet fill that fast.

I've been grappling with the air lock issue since we bought the place back in 2011 (draining pipes, re-filling two, three times to get the toilet to work). So, I would have to disagree that air locks on a pressurized system are a myth (no disrespect). Then, there's the subject of air locks in a pressurized single-pipe radiator system which I had in my other home. Two years of rads not working (fully bled) and then suddenly - heat.

Air locks are nasty and a b**** to diagnose.

After running a direct line from the manifold to the toilet - it works perfectly. Didn't get to the bath/shower feed yet.

All of your comments regarding altitude vs. pressure are correct. By my calculation, I have an 8ft differential in elevation between the two tanks. With the system charged @ 60 PSI, I have 58 PSI at the satellite tank. All good.

The pump cuts out @ 65PSI, but then drops to 60 PSI and holds. Gauge, or dual tank circumstance?

It's the drop in pressure at the satellite tank that's the problem (down to 20 PSI sometimes) and the CSV may be the solution - regardless of the two-tank config - thank you, valveman.

Bannerman....as mentioned, the purpose of the second tank was due to the fact I couldn't get a straight answer to put one in or not. I ended up putting it in as the cost was minimal and was advised there would be less cycling on the pump.

However - with respect to all comments here - I agree they should be together (same elevation) and I may address that issue moving forward.

Question to the group here. I have a 4' vertical rise in the garage where this new setup is because of pipe heating wire. It comes up the wall 4' out of the ground taped to the pipe terminating at the thermostat.

Reading up, I learned that the run for these wires have to be straight, taped and complete for it to work properly. I didn't want to cut the pipe back and roll up excess wire for fear the line won't work.

Basically, I could cut 4' of vertical rise off the system were it not for the heating wire. Your thoughts......

The wife now wants a brand new shower/bath fixture. I can't win. Asked her to help handing me a few tools while I was on the ladder and she said she had to shave her legs......oh, the misery.

Thanks again for your help, guys...really appreciate it !

Todd

 

[Reach4]

Sorry, but you're just plain wrong.

One thing I don't believe in is having air in a plumbing system that keeps water "locked" from coming out of the other end for an extended period despite sending in 20 plus psi pressurized water into the piping. Is that the thing Todd was talking about?

A real air lock does occur with a sump pump when the water in the pit empties, and air is in the pump. Something such as a check valve above blocks the air. Rising water cannot get to the impeller to get pumping. I was under the opinion that Todd was not talking about that.

Air locks are nasty and a b**** to diagnose.

What say you Todd? Yes, air locks can occur in a hot water heating system, but I don't think they exist in normal bathroom and potable plumbing. In the heating system you are not opening a faucet etc to the atmosphere. It's pretty sealed up.

You were talking about regular getting water for use in a house.
What symptom did you think "air lock" was doing to you? Making the water get to the toilet slower? Long small, and possibly clogged, pipes did that.

 

[The Todd Man]

Yes, closed, single loop system. When you're dealing with stuff installed (and subsequently modified) since the 40's - when single in lieu of twin-pipe were installed to save $$$ - you have your work cut out for you.

This air lock was on a regular potable water system and the worst install....ever. And yes, it existed. Bad plumbing work is my best guess, but the problem did exist nonetheless. I can't argue nor defend that point any further.

As there's seemingly some controversy regarding this subject not really related to the initial post, I'll only offer this comment:

As a resident of six provinces and seven cities in Canada, I've seen a plumbing air lock or two along the way.

Read instructions carefully before installing.

Product may not be as shown.

Batteries not included.

See dealer for details.....

 

[Reach4]

The pump cuts out @ 65PSI, but then drops to 60 PSI and holds. Gauge, or dual tank circumstance?

I think it is normal for the pressure to drop a bit. I attribute it to the diaphragm relaxing having been stretched a bit.
https://terrylove.com/forums/index....-i-lose-3-5-lbs-of-pressure-at-cut-off.67940/

In your dual tank system there is an additional factor. The other tank is accepting water from the main tank so there is a little more drop.

 

[LLigetfa]

I attribute it to the diaphragm relaxing having been stretched a bit.

Not likely. The two tanks are equalizing after the pump shuts off. It is to be expected when there is a long run in between the two.

 

[Bannerman]

I didn't ask the reason for the second tank, I asked why it was located so far from the first tank. Some people misunderstand the purpose of a pressure tank and sometimes expect it plays a different role than it actually does. It is often best to establish a person's intentions, thought process and conceptions before attempting to appropriately answer the initial question they posted.

As the 2nd tank will supplement the drawdown capacity of the first tank, I would suggest locating both tanks together as Valveman recommended. If you are considering a CSV, then one tank will be sufficient. While one of your existing tanks may likely be used, usually only a 4.4-gallon tank will be all that is needed for an average residential application, to optimize the performance of the pump and CSV combination.

If the 2nd tank is relocated to the 1st tank location, or if a CSV is utilized, then the current 1" polyline >2 parallel 1/2" copper > 1" polyline could feed a manifold in the new section of the home, which will branch off to cold faucets and the water heater, at the same pressure as the remainder of the home.

I anticipate the 2 parallel 1/2"copper lines should provide similar flow to a single 3/4" copper line unless one or both copper lines are partially crushed or kinked below ground.

 

[Reach4]

Not likely. The two tanks are equalizing after the pump shuts off. It is to be expected when there is a long run in between the two.

How would you explain my data in https://terrylove.com/forums/index....-i-lose-3-5-lbs-of-pressure-at-cut-off.67940/ ? Single 44 gallon pressure tank.

I know you would not clearly say that it is not normal for the pressure in a single tank system to drop a bit. Todd is getting the sum of effects, and the remote tank is probably the bigger componant.