PDA

View Full Version : air in catchment plumbing system



craigwatanabe
September 14th, 2011, 02:42 PM
I'm totally perplexed. Suddenly my catchment pumping system is spitting air in the water piping system in my home. At first I thought it was the supply line from the tanks. Solid, no leaks and plenty of water in the tanks. So far I've changed out virtualy everything from:

1. The pump itself
2. The pressure tank
3. Entire outside plumbing from PVC piping, valves, check valve (coming from the supply line), filter canisters
4. Even installed a check valve on the cold water inlet to the hot water heater.

I'm wondering if my system is fully purged of air? The air is coming from somewhere. I thought it was the water heater so I installed a check valve. There is no leaks anywhere as the system stays pressurized overnight. But as soon as you turn on the water, air spits out despite the pressure tank fully filled with water, the water filters showing no signs of air in them (clear canisters). When you shut off the water, you can hear water dripping in the water lines as if there's no water in them.

Now when I shut off the cold water supply valve to the water heater, the problem goes away. Aha! so I think that's where the excess air is coming from! So I install the check valve on the cold water inlet and hot water outlet thinking that will solve the problem. Problem is worse now.

Am I not purging the system correctly? When I installed the new plumbing system, I primed the entire system from the pump outlet back to the supply line to the tanks. I cracked open the farthest cold water valve in the home and started the pump. Slowly the water filled the lines and the air stops spitting and the pump pressure hits 60PSIG and stops. I shut off the water valve and the pressure tank slowly repressurizes the plumbing system. The water filters show water draining into the water line in the house then it stops and begins to fill up as the pressure tank releases water pressure. The pump turns back on when the pressure drops to 40PSIG and shuts off at 60PSIG.

Now I'm thinking the system is fully purged of air and is correctly presurized to 60PSIG. I go inside and turn on the water and air spits out again!

1. Absolutely no water leaks before or after the pump system.
2. Totally new plumbing from the catchment tank to the water line going in the house.
3. Installed a water bib before the filters but after the pump. No air in the water as I open that bib.
4. Air seems to be introduced inside the house somewhere but no leaks.
5. I'm still suspecting the water heater as it's the only vessel in the pressurized system that could possibly hold that much air.

Help!

Amati
September 14th, 2011, 09:25 PM
Wow, so is this life on the Big Island with a water tank? :eek:

tutusue
September 14th, 2011, 10:10 PM
Wow, so is this life on the Big Island with a water tank? :eek:
What? You haven't watched House Hunters on HGTV?! :D

GeckoGeek
September 15th, 2011, 07:04 AM
A couple of thoughts:

You need to post this in a forum for people who have catchment systems.

Since there are no leaks, I'm thinking the air is being introduced in the catchment/suction side of the pump. Besides, I can't see how air is getting introduced into a pressurized system. But it's not visible "air bubbles" but mixed in the water. It's "coming out" when it sits. Since the water heater is the biggest tank, that's probably where most of "coming out" happens.

I'd start by looking at how the water is pulled from the catchment to see if something about that is "aerating" the water.

If it was just failure to purge the system properly, I'd expect it to go away after awhile.

GeckoGeek
September 16th, 2011, 08:37 AM
I'm wondering if my system is fully purged of air? [...] Am I not purging the system correctly? When I installed the new plumbing system, I primed the entire system from the pump outlet back to the supply line to the tanks. I cracked open the farthest cold water valve in the home and started the pump.

In addition to the farthest valve, you need to think of the highest point in the system, since that's where the air is going to migrate to. Also, you'll need to open up a hot water valve to get rid of any air that's found it's way to the hot water tank.

craigwatanabe
September 28th, 2011, 12:14 AM
I've tried all that was mentioned. I'm suspecting the water heater as the source of all the air and have checked the suction line for leaks. Nothing there. This is very perplexing.

GeckoGeek
September 28th, 2011, 08:00 AM
I'm suspecting the water heater as the source of all the air

I can't see how a tank could be a "source" of air in a pressurized system. Failure to purge, yes. A point for air mixed with water to collect, yes.

Source? No. Not unless some part it becomes a vacuum.

Wild question: is the heater plumbed the right way? The cold water inlet should go down toward the bottom of the tank. The hot outlet should be pulling from the top. Get that backwards and you'll have problems purging.

craigwatanabe
September 30th, 2011, 11:07 AM
it's plumbed correctly. The water heater has worked flawlessly for the last 9-years already. Cold water inlet is plumbed correctly.

There are no leaks after the pump as overnight it doesn't come on. Line pressure stays above 50-PSIG throughout the night.

There's so much air coming out, even after the pump is running air continues to spit out. At first I thought maybe the pump is cavitating but installing a water bib and shutting the water valve feeding the house provided solid water flow with no aeration. Then I thought maybe it's the water filters (they do have an air purge manual valve. No leaks, no suction from the valve body.

So the problem has to be somewhere in the house. Since there's no leak (the pump doesn't come on and line pressure stays high), the only sources of pressure are the lines themselves, or the water heater.

An external leak from either of the two would have caused the pump to turn on from loss of downline pressure. It doesn't.

The water heater is the only device that I can think of, other than the mixer valves on the showers.

salmoned
October 1st, 2011, 12:02 AM
From your previous comments, it appears the only source of replenishable air in your system is dissolved air that is forced out of solution when the water is heated. An automatic air-purging valve may be installed if the need for manual purging is too frequent.

GeckoGeek
October 3rd, 2011, 10:01 PM
So the problem has to be somewhere in the house.

I disagree. Air can not get into a pressurised system. Not unless it comes in contact with compressed air. I think it's a case that your testing is failing to uncover the problem, so you're concluding it's somewhere else.

It's either a failure to purge or you need to test the pump under different flow conditions to spot what's going wrong.

craigwatanabe
October 4th, 2011, 04:58 PM
I'm thinking my testing methods are askew somewhere but I've had two plumbers look at it since my last post and they're as dumbfounded as me. :confused:

GeckoGeek
October 4th, 2011, 11:09 PM
I did a bit of googling, and saw a post from a guy who had a well. It was a cracked pipe in the well that caused air to get in when the pump shut down. If your pipe goes into the tank "over the top" it could be simular.

How's the pressure tank? Another suggestion was that the bladder had ruptured and air was getting into the plumbing that way. Eventually it looses all the air and the pump starts to short cycle.

craigwatanabe
October 7th, 2011, 07:39 PM
My suction line is intact from the catchment tank to the pump.

My pressure tank is working good, the bladder is holding 29PSI of air pressure as recommended. The pump isn't "short-cycling" either. That did happen before with the original pump system so I know what you mean. I wonder if I put a glass sight glass on the suction line to see if that over the top possibility could be the problem. You wouldn't see any leaks when the pump is stopped because gravitiy would simply pull water down the pipes instead of thru a leak at the top of the bend. Tomorrow I will check those pipe locations. Thanks for the suggestions.