Webtrol H10B8SS Pump Question 1

[PurewaterGuy]

Looking at the literature for the Webtrol H10B8SS Pump it states the pump works best in the 8-10 GPM range and will max out at 18 GPM.

My problem, The pump is producing 14-15 GPM and I cannot seem to get the pump down to the 8 GPM range. Any questions or suggestions appreciated.

 

[bimr]

I would prefer to keep the loop and add the PO.

 

[PurewaterGuy]

I got a call of no water in the labs.

Checked out the system when I arrived and the pump flow gauge still read 14 GPM. Checked the labs - No water -

Went to the valve and made one revolution on the screw. Watched the pressure gauge on the return to the pump and it increased 10 PSI.

Returned to the lab opened the faucet and had water and air. Returned to the system and the flow gauge was fluctuating between 6-8 GPM. Possibly due to air?

Left a faucet open to purge the air from the loop. Instructed them to purge for 30 minutes and turn off faucet.

Waiting for call on flow gauge. I'm going back tomorrow either way.

 

[PurewaterGuy]

The pump is putting out 8 GPM now. That is the best flow-rate according to the Webtrol technical department. The flow at the faucets is good - even though there is no flow meter within the loop to know the actual flow -

The one revolution on the return valve must have created the back pressure on the loop and at the same time brought the flow-rate on the pump to where it should be .. Agree or disagree with this?

I don't understand what the other valve does? What purpose does it serve?

 

[bimr]

The other one probably controls the water pressure entering the loop from the raw water side.

Without that valve, one would think that the pressure in the loop would rise to the same pressure as the raw water.

 

[PurewaterGuy]

You've been a great help here and I really appreciate that.

Now for the hard part. I really gained nothing on my final filter for pressure. At Initial start-up I got 10-20 PSI. Do you think in order for me to gain greater pressure across the filter I should throttle the return valve even more? This would create greater pressure in the loop correct?

BUT, if I do that it will obviously have an effect on the pump flow-rate as evidenced by the adjustment I just made in which the pump flow-rate dropped to the much more desirable 8 GPM.

Do you think it would be wise to also turn in the screw on the valve for the raw water entering? I'm inclined to believe the two must work as some sort of balancing act (so to speak) Do you follow me here?

Yet another thing, the quality of water (I'm providing 18 meg) is down to 15 meg currently. What type of havoc do you suppose the PVC pipe loop is creating pertaining to the water quality?

I hope you can take the time to answer each of these questions.

 

[bimr]

Are you asking about pressure drop across the filter? The final filter should not have much head across the filter unit because your water is essentially particulate free. I do not think it is advisable to have greater head loss either. You have a greater risk of filter breakthrough. The head loss should not increase much during the run either. The filter should be periodically backwashed or replaced depending on whatever type of filter that you have.

If you are talking about a need for greater pressure in the loop, then you need to adjust the valve more. That will restrict the discharge from the loop and the pressure will rise as the pump operating point moves left on the pump curve. This operating step is a balancing act because if you restrict the flow too much, the loop users will run out of water even though the water pressure is higher.

The valve for the raw water entering should be set for slightly more than the total capacity of all of the loop users combined plus 5 GPM (minimum flow in a 1" line). It would be helpful to have a flow meter on the line for monitoring.

If you only have 15 Meg water, you probably should install a mixed bed cartridge in the loop to polish the water. This would use non-regenerable mixed bed resin and you should run the mixed bed at a flow rate higher than the flow rate for working mixed bed units. Since there is so little material in the water, this mixed bed will run for an extended time.

I don't think that the use of PVC would drop the water quality that much.

 

[PurewaterGuy]

The final filter is a replaceable 30" 0.2 Micron with 222 O-ring.
The filter pressure brings me yet another question. If the pump is rated at 8 GPM for best performance, wouldn't you agree the loop was most likely designed for the flow-rate I have going through it now? I realize there is no flowmeter for us to know the true rate. I will install a flowmeter, I have selected this Blue White Flowmeter with 1" connections.

Question regarding the "total capacity of all loop users plus 5 GPM" ,, If all the faucets are the same, If I know the maximum output of one faucet, then multiply by the number of total faucets, will this give me the maximum output?

As for the mixed beds, I currently have a total of 9.6 cubic feet of mixed bed resin inline. Granted 4.8 cubic feet is on the feed side but it still enters the loop feeding into the post pump side where it is polished by another 4.8 cubic feet. (The system drawings show this)

I don't understand why the quality would drop so fast. Perhaps I am getting a chloride breakthrough at the carbon tanks? Thoughts.

Or perhaps the water is not recirculating at a rate that I am getting the full benefit of the tanks. Perhaps channeling is taking place?

As

 

[bimr]

It seems reasonable that the pump was sized at a lower gpm, not the maximum 14 gpm.

Correct, if you add up all of the faucets plus add the minimum flow in the line will give you the maximum output. You need more flow than the total of all faucets so that the loop will continue to flow when all faucets are open.

If you are not getting 18 meg out of a mixed bed, there is a problem and you need to change the resin. You should be using non=regnerable resin.

The breakthrough from a mixed bed is not chloride. The breakthrough will be in the form of ppb Sodium Hydroxide.

It is possible that you may have channeling, but that is unlikely.

 

[PurewaterGuy]

"plus add the minimum flow in the line"

How would I know what this is?

If I experience chlorine break through after the carbon tanks it will make the mixed bed deionizers work harder during the exchange process, correct? That has been my past experience.

I don't buy the channeling either but thought I'd throw it out there anyway to cover all the angles.

Why do you think I should be using virgin resin as opposed to regenerated? There are draw-backs to virgin resin.

 

[bimr]

Mminimum flow is that flow that will provide 3-4 ft/sec flow velocity.

It is probably impossible to get chlorine breakthrough through the carbon filters. Assuming that the carbon filters are correctly operated.

Virgin resin will provide you the best quality water and will not contain any of the regeneration products or leakage. There is some inefficency in regeneration of mixed beds. Thus the water quality will not be as good from a mixed bed compared to virgin resin. VIrgin resin has cation resins and anion resins regenerated separately and then the resins are intermixed.

 

[PurewaterGuy]

"Minimum flow is that flow that will provide 3-4 ft/sec flow velocity."

Wouldn't it be necessary to know the pipe length and diameter in order to calculate this?

If so, I have no schematic of the pipe layout, how would I achieve this?

I have always had a very high success rate using regenerated resin. So long as it reaches spec after regen at the plant.

Virgin resin is not good for applications, so I am told. Specifically in dialysis applications due to the release of Amines. Have you heard of this?

 

[bimr]

That would be about 9 gpm in a 1" diameter pipe. Q = VA.

http://www.ndt-educational.org/images/Hemodialysis 1 Section IV.pdf

ONe would think that you need a sterile ystem and high quality resin for dialysis. You should talk about the amine issue with the resin manufacturer.

 

[PurewaterGuy]

I know what the guidelines are for Dialysis. It all falls under RD52 ,, In 15+ years I've never failed to meet the AAMI water guidelines, actually I have produced better water quality every time than what the spec calls for. I was told once Amines from virgin resin are not good for dialysis patients. I've never seen any literature on this before so I thought I'd just throw this out there and see what responses came back.

"That would be about 9 gpm in a 1" diameter pipe. Q = VA."

Kind of lost me on this volume equation. If I don't know the footage of the pipe loop, How would I be able to determine what the minimum flow should be?

I suppose I could go back to what we've said previously, calculate the maximum flowrate of a single faucet, multiply this by the number of faucets, add in any equipment that could possibly draw water as if the equipment were running with every faucet open (glasswash equipment ect) and add in the additional 5 GPM you mentioned. Do you think this would give me an accurate picture of what the flowrate in the loop should be?

 

[bimr]

Convert gpm to cubic feet per sec. That is Q. Eaample: 9 gpm = 0.02 cfs

Divide by area of pipe in square feet. That is A. Area of 1" diameter pipe = 0.00545 square feet.

Q/A = ft/sec. 0.02/0.00545 = 3.67 ft/sec

 

[PurewaterGuy]

"calculate the maximum flowrate of a single faucet, multiply this by the number of faucets, add in any equipment that could possibly draw water as if the equipment were running with every faucet open (glasswash equipment ect) and add in the additional 5 GPM you mentioned. Do you think this would give me an accurate picture of what the flowrate in the loop should be?"

Can you answer this question for me?

 

[bimr]

Yes that is correct.

 

[PurewaterGuy]

OK. Thanks so much. I'm going to be concentrating fully on this system next week. I'll have lots of information and data to share ,,, and of course more questions ,, Have a great weekend and thanks again!

 

[PurewaterGuy]

I just installed a POU system with DI, UV and Ultrafilter. Looks like they want to shut down the loop system.