Help! Water pump pressurizing when using hot water tank.

[bondj007]

Decided to be a little proactive and replace my water pump. After install of my SHurflo 4008 I determined that my check valve on the hw tank needed replacing. That statement is simplifying 2 hours of water system tests, looking for leaks etc) Went to replace it and of course couldnt get it out like most people have experienced - so pulled out the guts of the check valve with pliers and put another new plastic check valve in line. New check valve works fine. New pump works fine.
Here's the problem. When pressurizing up the system, everything works perfectly if I have the hw bypass 'on'. RUn a tap, water comes out, turn the tap off, pump shuts off immediately. If the hw bypass is 'off' - and i'm now using water from the hw tank - after closing a tap, the pump will run for 3-5 secs before reaching pressure and shuts off.
So - hw bypass on - the pump will shut off as soon as i close the tap. Hw bypass 'off', pump will run for 3-5 secs after closing tap. What's going on here? I'm at wits end after an 8 hr project. Help appreciated guys - I can't solve this one and we're trying to go out this coming weekend!

[bondj007]

Hmmm - Good point, however the one thing that confuses me is the pump pressurizing delay also happens when just running cold water - ie nothing should be coming from hw tank but still takes 5 secs to pressure up when hw tank bypass is off. Why would this be?

[Bobbo]

The water heater has 6 or 10 gallons of volume that need to be pressurized. Takes a few seconds.

Take a bicycle air pump and inflate a bicycle tire (small volume) by 1 additional pound. Do the same for a car tire (large volume) and see how many more pumps (extra seconds) it takes.

[bondj007]

Sigh - air bubbles seem to be a red herring - Old-Biscuit you got me thinking so I removed the strainer completely - no more air bubbles. Thank you. Problem is the 5 sec pressurization problem still persists. HW by pass on, pump shuts off immediately when closing tap; by pass off - takes 5 secs to pressurize. Water hammer on cold inlet pipe to hw tank. On the good side - something clearly not sealing properly on the filter so will replace.

[Old-Biscuit]

Air is getting into system

Only place for air to get in is on the suction side of pump (discharge side of pump is pressurized and any 'opening' water would leak out vs air getting sucked in

Suction hose has a crack
Pump strainer has a crack or is not sealing around top/gasket
Pump inlet fitting cracked/sucking
Pump case is cracked

Winterizing valve/hose/connections are sucking air (if you have a winterizing kit on suction)

Air is getting sucked into suction side of pump..........

[bondj007]

Last troubleshoot of the evening. Took air compressor at 30 psi and blew air back down supply tube into water tank with the thought to get rid of any air lock or air bubbles trapped that the pump couldn't draw out. No help.

[bondj007]

screen/filter on inlet side of pump checked - clean. Inlet connections on water pump rechecked and tightened. No change.

[bondj007]

for anyone following along I'm posting every piece of info i find in my troubleshooting. Bubbles present in outlet and inlet, pump still shuts off immediately when hw bypass is on. Still 5 sec delay to pressurize when hw bypass off. Air bubbles going into hw tank causing? I'm reaching now I know....

[bondj007]

Note when posting about bubbles tank at 1/3

[bondj007]

when opened up for 4 or 5 minutes, hammering goes away. SHut off the last tap and the pump shuts off immediately. Perfect. However - Repeat opening another tap and within a short time - hammering comes back - open everything, let run, hammer goes away. Just noticed that through flex tubing, I can see a persistent stream of pea sized air bubbles on the outlet side of the pump. Not persistent on inlet side. ???

[coolmom42]

Every time I've had water hammer, there is air in the lines. Open up everything and let it run for a few minutes while.

[bondj007]

Thanks for the diagram Old-Biscuit - Additional notes - have flex pipe on inlet and outlet. Have tried 'trial and error' on adjustments with pressure settings on pump - little change - shortening of 3-5 sec pressurization to 2-3 secs maybe. Water hammering is on 4-5 ft hard pex line after looped flex outlet line reaches hard pex distribution lines. So frustrating! Maybe I'll try staring at it some more.

[Old-Biscuit]

blangen wrote:
Air in the HW tank. Pull the pop-off lever and let the air out. Or open the highest valve and let run to remove air.

Air pocket in WH SHOULD be there..it is by design.

Water swells when heated.
Water can NOT be compressed...air can
W/O air pocket pressure will increase inside hot water tank/system causing TPRV (Temp/Press Relief Valve) to weep

Air Pocket is good




On Edit:

Shurflo 4008 is a 55 psi pump

You may need to use 'flexible' suction/discharge lines IF pump is plumbed with hard PEX (discharge line to cold water header)

And you may need to install an accumulator tank

[bondj007]

Thanks for quick reply blangen - Thought that might be it but no luck - hot water taps run in trailer for several minutes - no air pops coming out any longer. Other symptom - Lots of water hammer on the cold inlet pipe to hw tank. (5 ft section) Vicious rattling has me concerned a seal will be compromised over time.

[blangen]

Air in the HW tank. Pull the pop-off lever and let the air out. Or open the highest valve and let run to remove air.