waterfall in pex pipes

nytolly11

Hi, I just had a new zone installed on the second floor in my house. Hot water baseboards with pex pipes connecting them to the boiler. Every time that thermostat turns on I hear water rushing through the pipes (sounds like a waterfall). It is so loud that it wakes up people at night. I bled that zone twice already. After each bleeding the ‘waterfall’ stops for a day and a half and then it returns. In addition to air bleeder on the boiler I had one installed on that zone as well but it doesn’t help as it only releases very little air.
Any suggestions on how to stop this?
I don’t have the same sound on my existing zone on the first floor but that zone is full copper.
Thank you.

JUGHNE

What is the read out on the pressure and temp gauge?

nytolly11

I have the temp set to around 180 and pressure during boiler run is around 22.

JUGHNE

What is pressure when off and cold?

nytolly11

I can double check this but I think it is the same as there is almost always one zone is running. The new zone running only in the evening while there other is during the day.

Jamie Hall

Sounds like a pressure problem -- and it could be two at once, which is always interesting. First, you need to check the system pressure when it is cold or cool. Second, you need to look at it warm; there should be some difference, but not that much. 22 psi at the boiler should be enough to get a nice stream of water from the bleeders on the second floor -- but if the expansion tank is big enough to hold the pressure or is defective, you could be pulling air in or at least trapping it at the high points when the system cools down.

JUGHNE

Are there any air bleeders on the new baseboard heaters?

nytolly11

Yes. I mentioned in my original post that I had one installed after the fact at the furthest point on that zone on the second floor. When I try to release air it only releases very little before water comes out. My expansion tank was checked about a month ago. I was told that it is ok. One thing though is that this expansion talk used to support 2 zones only and this is a third zone that was added. Can it be not big enough?
The air bleeder valve that sits above the expansion tank was replaced about a month ago.

JUGHNE

Pictures of around boiler? Different angles from a ways back.

kjl520

I would suspect that you have a leak on the suction side of the pump. This will cause air to be pulled in by what is called the "veturi effect." If you did properly bleed the lines (which I'm not sure you did because I never saw you mention a garden hose) this would be the only possible cause.
I am concerned that you did not bleed the pex lines properly. Usually with pex I have to "purge" them. That is the process of sending fresh water through the lines, pushing out all the air. Then when you are confident that there is no more air you close everything. Leaving you with %100 water in the line. We would need to see a picture of the system in order to know if it is possible to "purge" the lines.

hot_rod

Make sure there isn't a valve partially shut off somewhere restricting flow.

Sounds like you don't have enough flow volume to shove that air back.

got a good air separator in the system? Pumping away from the expansion tank?

nytolly11

I will upload some pictures tonight but to answer kjl520 yes, I used garden hose to bleed that zone then I check the flow in the bucket of water until I saw no more air coming out. During the bleeding I shut off the the return valve as well. I also used a fast fill on the boiler to get the pressure to what it was before and check the bucket again to make sure there was no air. Also, if I didn't bleed a system fully I would hear the air right a way, no?
But it takes day and a half for the waterfall sound to come back. I heard that I need to bleed a system fully up to 3 times. Not sure if this will help though.

nytolly11

@kjl520, how would i know if I have a leak on the suction side of the pump?

hot_rod

If you fill and purge with cold water, as the water heats, additional micro bubbles will come out of solution. Small bubbles merge into large bubbles

You need a good central air purger, ideally a micro bubble type to keep working after the initial purge.

Send some pics of the near boiler piping.

nytolly11

@Jamie Hall and @JUGHNE - pressure on cold not much less then 22. Maybe 21.
@hot rod attached see pictures of my expansion tank and the air bleeder on the top, connectors next to it and the picture of the new zone pump. Can't get a clear picture of the side of the boiler and there is not a lot of space.

nytolly11

nytolly11

Mark Eatherton

Your pump is not in the ideal location. If you move it so it pumps away from the expansion tank, your noises will go away, guaranteed. The pressure drop through PEX is very considerable, which is a part of the problem. Between the incorrect pump position and the high pressure drop, it is setting up a situation whereby it causes air to come out of suspension, even though you force purged it.

You could move the expansion tank connection, but it would probably be more work than moving the pump.

ME

hot_rod

That is not my favorite type of air purger, it struggles to remove micro bubbles. It should have 18" or so of straight pipe up stream. Close to the ell like that further reduces it's effectiveness.

Sometimes increasing the fill pressure a few lbs can help rid problematic air, it squeezed the bubbles and helps then flow back to the purger.

nytolly11

@Mark Eatherton my taco pump (2nd picture) is all the way down below on the same line with other pumps. Not sure if I can move it.
@hot rod can you tell me what air purger would you recommend for a three zone residential system? Also, my relieve valve is rated to 30psi. My current pressure is around 22psi. Is it ok to increase the pressure to be close to 30 in this case and if yes can it affect my existing zone that is full copper?

hot_rod

it would involve some piping change, you could both install a micro bubble eliminator and move the expansion tank at the same time.

I suggest any of the micron-bubble type, Caleffi Discal is my favorite.

The expansion tank should be near the inlet side of the circulator pumps.

I would not increase the pressure any.

nytolly11

@hot rod Just so I get the right one are you talking about 551 air separator? Is it going to be in addition to mine or instead of and do you have any diagrams on where would I position in in my system with regards to my expansion tank, etc?

Ironman

The circulator should "pump away" from the expansion tank, not towards it.

When it pumps toward it, the pressure differential that the circulator creates (say 7 psi average) is DEDUCTED from the static fill pressure (usually 12 psi). This means you would have 5 psi near the boiler when the circ is running. It takes .434 psi for each foot that the water must be lifted. If your highest radiator is 20 feet above the fill valve, you would need about 10 psi to lift it. Then add 5 psi more to keep it positive at the top of the system. So that's 15 psi cold static fill pressure. When the circ starts, youre loosing 7 psi. Now the top of the system is in a vacuum and the air comes out of solution there.

If the circ is "pumping away" from the expansion tank as it should, its pressure differential is ADDED to the static fill pressure. So 15 psi + 7 psi = 22 psi at the bottom of the system - 10 psi for elevation = 12 psi at the top when the circ is on.



Dan has a book in the store on sight called "Pumping Away" which easily explains this principle and how to apply it.

Mark Eatherton also posted a video demonstration of this about a month or two ago.

Mark Eatherton

https://www.youtube.com/watch?v=tZRuqiQkukE

Without a doubt, one of THE most difficult technical propositions for people to see in their minds eye. Hope this clarifies it for those of you who don't believe it to be true, because your grand pa and your dad ALWAYS put the pump on the return.

Don't just make a difference. Make a POSITIVE difference.


ME

HomerJSmith

It appears that you have 2 taco pumps on your system.

A picture further back showing you whole boiler set up is more helpful.

An air scoop is fine, they have been used for longer than I can remember. It just take multiple passed, but the newer technology profits from the micro-bubblers and that's what I use now even tho I have several air scoops sitting on the shelf gathering dust. Just keep bleeding air. Every baseboard need a coin vent or hydroscopic air vent on the exit and they should be vented without the boiler running.

nytolly11

I actually have 3 pumps for 3 zones. One behind the other. It is hard to take a picture from that side. I will bleed that zone again but I think I need to put in a newer air scoop. Also, as far as I understand it is better to have a pump positioned not on the return side (which will be a lot of work to do for all three zones).

Ironman

It's not so much that the pump can't be on the return; it just should not pump toward the expansion tank which is usually on the supply as it is in your case.

You may be able to move the expansion tank connection to the return, UPSTREAM of the circulators, easier than moving the circs. See the alternate location in the drawing I posted.

An MBR (micro bubble Resorber), two short nipples + a union would replace the air scoop fairly easy.

Mark Eatherton

With three pumps, it is more difficult to give each pump a "look" at the PONMIPC, but I have done it. A $0.05 (nickel) fits perfectly into the bottom of a 3/4" copper fitting. If you drill a 1/4" hole in each of the three needed nickels, and then place a manifold across all three returns with the nickel in the bull of the tees, held in place by the 3/4" copper pipe, the pumps will "see" the PONMIPC (expansion tank) and will cause the pumps to make all positive pressure. For example, if the return line is 1", then use a 1" X 3/4" tee with the drilled plug nickel in the bottom of the 3/4" bull of the tee.

Just a wild guess here, but I'd bet you can probably get by with one pump, and install zone valves on the three returns. Moving the single pump to pump down stream of the air separator and expansion tank. But then again, that's just me, and I have the tools, skill and knowledge to make that work. If you did that, you'd also probably be able to get rid the three gravity checks that are on the supplys too.

Would need to know for sure how many radiators or heat emitters and their size in order to say wether or not it would work.

ME

nytolly11

Thank you but as you mention this requires more experience to accomplish this. Also, I don't know if I would want to change from 3 pumps to 1 as each of my zones is controlled by a separate thermostat and it gives me a flexibility(and redundancy) to heat a different sections of my house if one pump fails (as it happened to me ones before). I was reading through a Caleffi documentation on air eliminators and they mentioned that if a water pressure too high my existing air eliminator might not be able to catch all bubbles. The question that I have is by how much can I reduce the pressure in my boiler to test that theory?

Ironman

You don't want to reduce the pressure below 15 psi COLD static.

Please review my earlier post again until you grasp what was said.

Are you sure that you're not confusing velocity with pressure in the Caleffi info? Either way, it's not something that needs to be experimented. Cold static fill pressure is based upon system elevation, nothing else.

nytolly11

My cold static pressure is 22psi. boiler is rated for 30. Isn't it a little too high?

icy78

Mark Eatherton said:

With three pumps, it is more difficult to give each pump a "look" at the PONMIPC, but I have done it. A $0.05 (nickel) fits perfectly into the bottom of a 3/4" copper fitting. If you drill a 1/4" hole in each of the three needed nickels, and then place a manifold across all three returns with the nickel in the bull of the tees, held in place by the 3/4" copper pipe, the pumps will "see" the PONMIPC (expansion tank) and will cause the pumps to make all positive pressure. For example, if the return line is 1", then use a 1" X 3/4" tee with the drilled plug nickel in the bottom of the 3/4" bull of the tee.

Just a wild guess here, but I'd bet you can probably get by with one pump, and install zone valves on the three returns. Moving the single pump to pump down stream of the air separator and expansion tank. But then again, that's just me, and I have the tools, skill and knowledge to make that work. If you did that, you'd also probably be able to get rid the three gravity checks that are on the supplys too.

Would need to know for sure how many radiators or heat emitters and their size in order to say wether or not it would work.

ME

Mark, I am intriqued by this nickel idea. Is this for pumps that are on the return side and pumping towards the CSTees and towards the ex-tank?

icy78

I know in that previous post that the piping is wrong, but it is what it is, and I am wondering if you are referring to this type situation. Also I don't understand how the insertion of a restrictor would allow the pumps to see the point of no pressure change. Basically drawing a blank here LOL. (Embarrassed chuckle☺)