Are Check Valves needed for 2 recir lines returning to one pump?

JUGHNE

Redoing a domestic HW recirc system. The WH is between 2 areas of the building.
The North side has a 1/2" return line....the south side has the same.

I was going to add ball valves to each for balancing.
Would each return also need a check valve before teeing together??

The south end is then again split for 2 areas. The print shows balancing valves for each area at that split.
But shows no checks there.

The cold supply at WH will have ball valve, check valve, expansion tank then into WH.
The hot supply heads north and south.
The return line would go thru recir pump then check valve then into the bottom of WH.

Dave H_2

I would use a good balancing valve like this instead of the ball valve to control the flow. Actually a circ on each line is better for getting the flow in each loop. its just a pain to balance systems like these

Dave H.

JUGHNE

Dave, thanks for the response.
The budget is hard pressed for even one pump.
I have seen some drawings with checks on each separate branch before returning to one pump.
Wondered if any one has a reason.

Larry Weingarten

Hi @JUGHNE , The only potential for trouble I see is if the pump runs intermittently, you could get cooler water from one leg into the other at times, but even that may not be noticeable. Is the pump controlled or just 24 hour?

Yours, Larry

ChrisJ

I'm doing something similar in my house and will just be using ball valves and no check valves. There's a check valve going into the tank of course, just not on each line.

I run the pump on an aquastat, no timer. Only one loop has been running so far, so I can't give results, just my plans.

hot_rod

This valve would both balance and reduce operating cost via the heat loss from the loop. Add a delta P recirc pump and also save pumping costs.
Yeah it cost more than a check or balance, but it also saves money and may well pay the difference.
If not I would use spring checks.

ChrisJ

hot_rod said:

This valve would both balance and reduce operating cost via the heat loss from the loop. Add a delta P recirc pump and also save pumping costs. Yeah it cost more than a check or balance, but it also saves money and may well pay the difference. If not I would use spring checks.

I've never looked to see how much it costs to run my Taco 006 for a few minutes at a time, but something tells me those would never come close to paying for themselves?

A quick calculation and I came up with $6 per year to run the pump with just the aquastat.  The worst I could come up with was $14 per year but I don't think it runs that much with all of the insulated pex.


Is my math horribly off?  It happens.

JUGHNE

This will be run by aqua stat.
Probably will go with ball valves and spring checks.
School district strapped for money...as many are.

hot_rod

8- 10 bucks buys you a 1/2" globe valve, even the box stores sell them.
That would be the best valve, especially if you start choking it down much.

motoguy128

I have this same setup. Recirc lines running to multiple fixtures in the home and two main branches come together before hte pump.

Here;s the problem. 1) the Little eco circs that most people use don’t have much head and may not be able to open a spring check. So you’d have to use a swing check. I had it cause severe chatter on spring checks in my mixing valve. I removed them and ultimately deleted the mixing valve altogether.

2) without check valves at almost every fixture, inevitably, you get back flow between lines. I find that if I have 130 or 135F hot water temp, It’s getting mixed with 110-120F recirc water and I get about 125F water.

JUGHNE

Thanks to all for responses.
The pump in mind was a B&G NBF-22.
Or would the B&G NBF-12 be more suited?

hot_rod

The smallest pump that can get the job done is one rule of thumb.
The pumps needs to move just enough gpm to assure the furthest fixture see DHW a few degrees warmer than what it leaves the tank at.

Un-insulated lines, piping in cold areas will take more gpm and pump.

Or get a guesstimate on the length of the loops and size it that way.

If a pump replacement is in the card look into some of the smart recirc pumps that uses sensors and algorithms to calculate ideal flowrate.

JUGHNE

I certainly agree on only needing a very small flow.
Even a good dripping hot faucet will keep the hot water moving to that point, anyway.

On another job a few years back, we replaced water heater system in a small 17 bed hospital.
The old recirc pumps were 1/6 HP 10 GPM @ 10' head.
The maint man saw the little B&G NBF 25's compared to the old and thought they would never work......that started to instill doubt for me.
The building had been remodeled several times and involved 100's of feet of piping for hot water.

With the new WH on line but recirc pumps not plumbed in yet, I connected a hose to the return and after priming the return let the smallest stream possible run down the drain overnight.
The hot water was available immediately at the farthest hand sink for this duration.
The little pumps have been doing their job for 4 years now.