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]

Yup - I've learned a few things on this one - namely the fact of how my new pump works. 🙂

[RJsfishin]

I just started reading this thread, and just a few posts into it, I wondered, "what is broke ?" And as I read on, all the posts that explained that nothing is broke,....to no avail I mite add, I kept asking, "WHAT IS BROKE" ?
Fanally, after 3 pages, it is understood,.....don't fix what ain't broke !
Yes, I have the same replacement pump,....not that I am proud of that pump. But as long as the screws don't keep coming loose, and it doesn't heat up and shut off in the middle of a shower, count your blessings !

[Bobbo]

bondj007 wrote:
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?

There is no check valve on the cold water line going into the water heater. When you open a cold water faucet, the cold water line pressure drops, and the water heater pressure drops too.

[rwynkoop]

This is normal operation. Mine does the same thing. The hotwater tank acts as an expansion tank, when in bypass my pump cycles very quick with low water flow.

This in a response to the original post only.

[bondj007]

ok - water strainer replaced - cavitation/water hammer 95% gone. Am happy about that. Will accept new performance behavior of this model of pump - just may take a while to get used to. I find this pump much quieter than the old model however likely has something to do with flex tube i added to inlet - always just had on outlet.
Off to hardware store to buy pressure gauge but am comfortable I have not increased pressure. In my trial and error I made sure to net out on adjustments that were lower than factory but admittedly dont know where i ended up in terms of a number. Will be nice to know and re-adjust to factory levels.
Unless something drastic happens this coming weekend I'm going to call this thread done and solved. A heartfelt thank you to all who chimed in to help my thought process and trouble shooting path. Has been a while since I've been on the forum but will never forget what a helpful group of supporters there are here. Thanks all. J

[Old-Biscuit]

bondj007 wrote:
OEM was shurflo 2088-422-144 - 30 psi inlet, 45 shut off vs 55 for the 4008 as you mention. I've done a little trial and error on setting the pressure switch so not sure where it sits at the moment. What would be the consequence of going to a higher rated pump?

The 4008 is the recommended replacement for the discontinued 2088 model.

The higher discharge pressure is what you are not use to ......how it sounds/reacts when pump stops

Course.......messing around with -adjustment- can result in HIGHER pressures. Did you have pressure gauge connected when adjusting?
Pump has an internal bypass which starts opening at 40# and is fully open at 55#.....unless you changed settings????

[Chris_Bryant]

I would leave it as is- if the pump running gets too long, then you can try raising the bypass pressure- but just a couple of seconds I would leave as is.

[bondj007]

Ok - things starting to make sense - but just so I understand this correctly... You're thinking leave everything as is? Or are you getting at trying to adjust bypass pressure down lower?

[Chris_Bryant]

That new pump is a bypass type pump- it has an internal bypass valve that recirculates water at low output demand. The idea is that instead of rapid cycling when you open a 2 gpm faucet with a 3 gpm pump, the pump runs continuously, and some of the water recirculates. there is an adjustment for the bypass pressure,, and I have had to adjust that, when a pump would not shut off.
That does make the pump act differently than the old one.
I wouldn't worry about the pressure.

[bondj007]

OEM was shurflo 2088-422-144 - 30 psi inlet, 45 shut off vs 55 for the 4008 as you mention. I've done a little trial and error on setting the pressure switch so not sure where it sits at the moment. What would be the consequence of going to a higher rated pump?

[Old-Biscuit]

bondj007 wrote:
Well, not sure to feel relieved or dumb that things are working as intended. I'm at work so am unable to verify however I suspect that the leaky strainer will resolve the water hammer issues I've been experiencing.
I am experiencing some of the accumulator behaviour that you guys speak of however I just don't recall this being the case in prior years. WHen I turn on the tap it's a good 2 secs before pump kicks in and a good 3-5 to shut off after tap close. All seems new to me however if it's working as designed, I'll try and let it go and go back to worrying about more important things. One more post later tonight to confirm water hammer gone and that may be the end of the thread. Thanks for all that chimed in to help me sort - greatly appreciated.

What was OEM pump that you replaced.....same model as current or different model?

Current one has a 55 psi discharge. (Revolution 4008)

[bondj007]

Well, not sure to feel relieved or dumb that things are working as intended. I'm at work so am unable to verify however I suspect that the leaky strainer will resolve the water hammer issues I've been experiencing.
I am experiencing some of the accumulator behaviour that you guys speak of however I just don't recall this being the case in prior years. WHen I turn on the tap it's a good 2 secs before pump kicks in and a good 3-5 to shut off after tap close. All seems new to me however if it's working as designed, I'll try and let it go and go back to worrying about more important things. One more post later tonight to confirm water hammer gone and that may be the end of the thread. Thanks for all that chimed in to help me sort - greatly appreciated.

[DrewE]

Chris Bryant wrote:
The water heater acts as an accumulator in the system, whether you run the hot water or not. It is working the way it is supposed to- if there were no air cushion, the system pressure would rise enough to trip the PTR valve on the water heater every time you heated water.

This is correct.

If you misset the winterizing valves for the water heater, it may be possible (depending on your setup) to have its entire volume act as an accumulator. That can lead to very strange behavior: having water pressure for a good long time after turning off the pump or city water connection, having the pump seemingly never shut off, etc. Don't ask me how I know this....

[Chris_Bryant]

The water heater acts as an accumulator in the system, whether you run the hot water or not. It is working the way it is supposed to- if there were no air cushion, the system pressure would rise enough to trip the PTR valve on the water heater every time you heated water.