Plumbers here??? Got circulating pump problem.

[turbodog]

The general consensus is - the pump impellors must have experience some cavitation - which cause the impellors to stop pumping watering at the rated amount

typically I won't buy a recir pump at home depot - try a plumbing wholesaler


all the best

I've got it on my 'todo' list to pull the failing pump and check it out. Would like to see what's up and need to get it out of the circuit.

As far as home depot goes. I agree the pumps there are no way as good as commercial pump. But, I did ok I guess. Got 7-8 years out of original Lowe's pump.

Also... having $2000 in HD gift cards influences my buying habits! Cashed in some Amex points!

Now... need new air compressor, sander, etc...

 

[turbodog]

Ok peeps...

Pulled old pump out, installed straight pipe in its place, and tore down old pump.

New pump working very well by the way.

Old pump had 2 paths through the pump. first was a main path, with a spring-loaded backflow preventer (BFP). Second path was smaller, fed from one side of BFP, and outputted on the other side.

Well, the BFP failed open. It was plastic and broke. So the pump was essentially just circulating fluid in a loop through itself.

Thankfully the new pump is not made this way. There's 1 path through it and the impeller is in the path. It's got enough space around the impeller for higher flow rates to bypass the impeller. I installed a copper/brass BFP in line with it so all is well.

Thanks!

 

[turbodog]

Further dis-assembly of old pump found something interesting. The impeller set on a spherical bearing atop a post. It was not driven by a shaft. Was induction driven. Guess there was no shaft seal to leak... now if they just made as good a valve assembly...

 

[Chauncey Gardiner]

It reads as though you have a pretty complicated system. At the risk of being rude, pictures please.

~ Chance

 

[turbodog]

https://drive.google.com/file/d/0B-gHbK9Ul8fyamp3c09HMURJeUE/view?usp=sharing

The old setup let the pump run cooler, being at the end of the return lines.

The new setup makes it hotter, but if it leaks, at least it drips onto the heater and runs down into the drip/overflow pan instead of coming through the ceiling I hope.

In case my wonderful drawing is unclear... the old pump had 'parallel' water paths through it. A small backflow/check valve was in it also (unknown to me). When this small valve broke it allowed water to endlessly circulate inside the pump.

 

[Matrix 100]

still new to forum's - sorry for the slow reply

your new set up is not the best way to pipe

your old set was better - but the BFP which you call is a check valve not a BFP should be on the discharge of the pump side

I am enjoying this thread - so I am going to provide you with a drawing - if I can figure out how to do it

- a check valve and BFP are very similar but different

Chauncey Gardiner - plumbing system are exactly like electrical system - a pump is very similar to voltage - water flow is similar to current - pipe friction is similar to resistance

If you understand electrical circuits - you will understand mechanical systems or plumbing

all the best

 

[turbodog]

still new to forum's - sorry for the slow reply

your new set up is not the best way to pipe

your old set was better - but the BFP which you call is a check valve not a BFP should be on the discharge of the pump side

I am enjoying this thread - so I am going to provide you with a drawing - if I can figure out how to do it

- a check valve and BFP are very similar but different

Chauncey Gardiner - plumbing system are exactly like electrical system - a pump is very similar to voltage - water flow is similar to current - pipe friction is similar to resistance

If you understand electrical circuits - you will understand mechanical systems or plumbing

all the best

At the time, I could not remove the old pump to do a straight pump swap. Could not find the fittings in time. The new pump screwed right onto the nipple leaving the heater... took less than 5 mins to install there.

I know it's not a check valve. I used a BFP term in case others did not know. I figured most people can understand what a BFP is, and it's close enough in workings in this deployment.

When you say original was better... you mean because of pump temp being lower there?

I can see check valve needing to be downstream from a pump... tends to keep pump from starving for water. Check valve got installed after original pump was installed... so the guy put it where it would fit, not where it *should* go I guess.

It all worked fine.... till the pump failed.

New one must flow more water. Temps are noticeably higher.

 

[turbodog]

Now my plumbing kit is complete: several new good pipe wrenches, fresh can of dope, etc...

 

[Matrix 100]

generally you always "pull" the water thru the pipe - not "push" the water thru

your first set up pulled the water thru the pipe

but in a low head situation which is what you have, it will not make much of a difference

which is why everything is OK

Turbodog southern USA - what state ??

 

[turbodog]

Pumps are at same elevation in both setups.

MS

 

[Chauncey Gardiner]

generally you always "pull" the water thru the pipe - not "push" the water thru

Which is it, generally or always?

~ Chance

 

[Matrix 100]

Let me see if I can clarify

On domestic water recirculation piping - always the recir. pump is on the return side
The view is the pump will be always pumping e.g. 2 gpm at a constant head
If the pump goes on the hot water side, when the taps open up, the head pressure changes
this will result in the pump wearing down faster - pumps are always designed for a constant flow and head

On hydronic heating systems pumps are always on the supply side of the boiler - pulling water thru the boiler

But you could say it's pushing water thru the pipe ( I stand corrected )

Turbodog's original pump was on the return side of the recirculation line - the better location

Turbodog - it has nothing to do with temperature or elevation

I only ask what state you are from - as it's on my bucket list to visit every state in your great union

Pacific N.W. - state ??

 

[Chauncey Gardiner]

Pacific N.W. The great state of Washington, Puget Sound region.
Aka, God's country.

~ Chance :twothumbs




As long as Mt. Rainier doesn't act up.

Then it will be as Leeloo and Korben said, "Big Bada Boom!"

 

[Matrix 100]

looks beautiful

haven't been to Washington State

 

[turbodog]

Let me see if I can clarify

On domestic water recirculation piping - always the recir. pump is on the return side
The view is the pump will be always pumping e.g. 2 gpm at a constant head
If the pump goes on the hot water side, when the taps open up, the head pressure changes
this will result in the pump wearing down faster - pumps are always designed for a constant flow and head

On hydronic heating systems pumps are always on the supply side of the boiler - pulling water thru the boiler

But you could say it's pushing water thru the pipe ( I stand corrected )

Turbodog's original pump was on the return side of the recirculation line - the better location

Turbodog - it has nothing to do with temperature or elevation

I only ask what state you are from - as it's on my bucket list to visit every state in your great union

Pacific N.W. - state ??

OIC now.

So, the original piping still could have been better. It ties into the cold intake into the heater. I'm sure it gets some additional siphoning when the hot tap open.

Really should have pump on return side and have it pipe directly into the (what?) popoff valve area?

We've had problems with hot/cold mixing when, say, 20 gals HW are used and then the tap is closed. The pump mixes the cold bottom water with the hot water and the whole tank drops to some middle temp. If it piped in at the popoff valve this would stop.

 

[Chauncey Gardiner]

Have instructions been provided with either of the pumps you've purchased?

~ Chance

 

[turbodog]

nope!

 

[Chauncey Gardiner]

Well that sucks, or blows, depending on which end of the pipe you put the pump.

~ Chance ....... who thinks he's funny.

 

[Matrix 100]

-the pump is on the return side of the recirculation line - ( you could say the pump is pulling water thru the recir line )
- then you add a spring loaded check valve ( very important)
then you pipe the recir line into the cold water line at the bottom of the tank ( add a tee connection )

Or pipe into the drain valve at the bottom of the tank ( remove drain valve and add a tee with a drain valve and tie recirculation line into tee)
this depends on the type of HW tank - you may not be able to do this, and it's not common practice

Don't tie the recir line into temp and pressure relief valve ( pop off valve) - can cause problems with relief valve

Unfortunately I don't think what every you do it will help on the hot/cold mixing problem - this is another problem
which is the recovery rate of your HWT - it's to low


On the flashlight front
just ordered a spy 007 from Data

 

[turbodog]

-the pump is on the return side of the recirculation line - ( you could say the pump is pulling water thru the recir line )
- then you add a spring loaded check valve ( very important)
then you pipe the recir line into the cold water line at the bottom of the tank ( add a tee connection )

Or pipe into the drain valve at the bottom of the tank ( remove drain valve and add a tee with a drain valve and tie recirculation line into tee)
this depends on the type of HW tank - you may not be able to do this, and it's not common practice

Don't tie the recir line into temp and pressure relief valve ( pop off valve) - can cause problems with relief valve

Unfortunately I don't think what every you do it will help on the hot/cold mixing problem - this is another problem
which is the recovery rate of your HWT - it's to low


On the flashlight front
just ordered a spy 007 from Data

I might relocate the pump to the return lines.

As far as hot/cold mixing... you would have to have instant recovery for that not to be a problem.

Say you have a 50gal tank, pull 10 gal out, and then turn off the tap. At this point the tank is stratified pretty well. Then, the pump will mix 10 cold with 40 hot if left alone. Recovery suffers because return water is flooding the bottom of the tank.