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Water pressure boost pump

Water pressure boost pump

Water pressure boost pump

(OP)
My off grid house is supplied with water from a tank about 6m above the shower head.

LONG BORING BIT This makes showering a rather minimal experience. So, first thought was to bung in one of those 120W shower booster pumps, which theoretically can belt out 9m of head . Then we looked at the spec of the yet to be installed instant gas hot water, and it needs at least 13m of head, and the plumber thinks that 24m is a more practical target. So we tried the pump and got some miserable pressure reading. The shower can run at 16 l/min, there is only one shower.

ACTUAL QUESTION

So we need to install a proper pump somewhere between the cold water tank at the top of the slope, and the house. Advantages of by the house are that it doesn't pressurise the downhill pipe (1 inch black poly), and it can just run off an extension lead, and pumps like lots of head on the suction side. Advantage of up the top is that we won't be able hear it. Electrical power is not an issue there either, but it is a little more complex.

This is a 35l/min 35m head pump I am concerned about waterhammer when the pressure valve trips.

So which is the best alternative (anybody saying to compromise halfway up the hill will be asked to leave)?



Cheers

Greg Locock


New here? Try reading these, they might help FAQ731-376: Eng-Tips.com Forum Policies http://eng-tips.com/market.cfm?

RE: Water pressure boost pump

I'd put it near the house, so that I could hear it when it's running and doesn't need to.
... which could easily occur if it was controlled by a manual switch near the shower,
and plumbed to just supercharge the heater and the shower.

Mike Halloran
Pembroke Pines, FL, USA

RE: Water pressure boost pump

Waterhammer is not an issue caused by stopping a centrifugal booster pump. Water will still flow pretty freely through the pump.

RE: Water pressure boost pump

Would it be easier to just install a submersible in the tank?

Keith Cress
kcress - http://www.flaminsystems.com

RE: Water pressure boost pump

Install pump and pressure tank - as typically used for a well - near the house so that the pump doesn't cycle on and off every time you open the spigot.

RE: Water pressure boost pump

(OP)
It'll be a pressure switched pump like this

http://www.ebay.com.au/itm/222131034508?_trksid=p2...

not manually switched.

OK, so I don't need to worry about waterhammer, and I don't want to install a buffer tank between the pump and the house.

A submersible is slightly more difficult to install, and the small ones I can put my hands on seem to only manage 9m of head, designed for draining pools etc. The bore pumps are rather terrific but use 1 hp or more which I'd like to stay away from.

Cheers

Greg Locock


New here? Try reading these, they might help FAQ731-376: Eng-Tips.com Forum Policies http://eng-tips.com/market.cfm?

RE: Water pressure boost pump

Are you looking at model QB 60, 1/2 HP?
Can you find a pumping curve for that pump?
Maximum pressure may not occur at maximum flow.
I strongly suggest adding a tank with a bladder such as:
http://www.ebay.com.au/itm/24-litre-Pressure-Tank-...
BTW that looks like a turbine pump. A centrifugal pump of that small diameter may not be physically capable of producing anywhere near the rated head.
I have serviced several installations which looked identical to the QB 60 pump mounted on a pressure tank similar to the one I linked to.
In both cases the bladder in the tank had failed and the pump was short cycling on the pressure switch.
In both cases, the pump motor had burned up due to rapid repeated starts.
In one sad case, the first repairman simply replaced the burned out pump without replacing or repairing the tank bladder. The new pump failed in less than a day.
If your flow rate under normal usage will exceed the pumps flow capacity at the working head, consider a larger storage tank.
Early pressure tanks used an air cushion. to give a reserve capacity and reduce short cycling.
The tanks were mounted vertically and a "Snifter Valve" mounted midway up the tank injected a small amount of air into the tank when the pump started if the internal water level was above the snifter valve.
Newer tanks use a precharged internal bladder to provide a reserve cushion.
The failure of either a snifter valve or of a bladder will result in short cycling and rapid motor failure.
Installing that pump without a reserve tank may lead to short cycling and early motor failure.
Another option is an inline booster pump such as:
http://www.ebay.com.au/itm/Domestic-Household-Elec...
A booster pump is typically controlled by a flow switch rather than a pressure switch.
water hammer may be an issue when the shower valve is turned off. It is not much related to the pump stopping but rather to the valve stopping a large column of water.
Water hammer may be easily mitigated by installing a tee in the water supply line near the final valve and installing 18" or 24" of 3/4" pipe vertically with an end cap.
The vertical pipe traps air and acts as a cushion to mitigate water hammer.

Bill
--------------------
"Why not the best?"
Jimmy Carter

RE: Water pressure boost pump

Do not install a tee and vertical pipe to mitigate water hammer. The air in the pipe will soon be absorbed by the water and then you just have a dead ended full pipe that doesn't do anything for you. Get a small water hammer arrestor that uses a piston.

RE: Water pressure boost pump

That pump appears to have a check valve on the outlet and then that pressure switch assembly above the check valve. That pressure switch assembly is likely a small chamber with a diaphragm or bladder which works like a very small pressure tank. I can't see it working very well unless you expect to have the taps either off or fully open. It will likely surge on and off rapidly if you try to run it at a low enough flow it can build enough pressure to turn itself off. It likely won't water hammer per say, but I would expect it to chatter and surge when the flow is low and you rapidly trip the pressure switch on and off.

RE: Water pressure boost pump

I've seen it a couple of times, Lionel.
In the cases I have seen the pump stopped and restarted every couple of seconds. The motor didn't last long. How long I don't know but in the instance where the pump was replaced without replacing the tank, it lasted less than a day.
I saw a similar failure where the pressure switch was on the pump discharge and there was too much length of piping and too much loss of dynamic head between the pump and the tank. That was an engineered installation with about a 15 HP pump. This would short cycle several times before the tank came up to pressure. This one lasted several weeks before motor failure.

Bill
--------------------
"Why not the best?"
Jimmy Carter

RE: Water pressure boost pump

I agree that a pump and pressure tank is the way to go on this. These are available as a single packaged unit.

RE: Water pressure boost pump

I agree the pump and bladder tank package is the way to go. I'm a bit concerned about your 1" poly line. What's your target flow rate and length of line? You might have to install the booster at the tank to have adequate suction pressure.

RE: Water pressure boost pump

Why not a pump and a cycle stop valve? No tank needed then.
16 l/min is a lot of water in a shower, I wish that mine had that, but I do have ok pressure.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, Plymouth Tube

RE: Water pressure boost pump

Geez Greg! I thought you lived in the American South West not Oz.

My utilities buddy who I do lots of rural water and filtration systems with hates pressure tanks because they're a hassle, take space, fail like clockwork, are hard to dispose of and replace, and cost a lot.

He completely avoids the issue by always using or specifying a packaged unit from one of the big pump companies. It's a small pump with a VFD built into it and a very small, very robust, bladder tank on the order of half-a-gallon. The unit uses the small tank merely as a capacitor to work its control off of and to give just enough delay to allow the pump to smoothly spool up to the demand. You set the pressure you want and forget about it. The unit is VFD'd so there is no damaging short cycling nor single phase motor failures. If the bladder fails you can continue to use the system, you will just get some delta pressure as the unit has lost its little capacitor.

The unit covers all flows equally well up to its limit. You use only the power needed to get the job done. There is no noticeable 20 PSI pressure cycling. It's single phase fed and comes in a couple of sizes. He's building his own Spanish Style house in the Monterey hills and has included another of these in it because years ago he dumped his pressure tanks and put one of these in the place he lives in now. I consider that a pretty strong endorsement.

If you're interested in this possibility I'll ask him who makes it.

Keith Cress
kcress - http://www.flaminsystems.com

RE: Water pressure boost pump

Assuming it's made in the States, I might be willing to pay the Canadian/US $ exchange rate on something like that; we use a bladder tank, but I suspect a perforation in the bladder as about once a year I have to take the system o/s, open its manifold drain valve to waste, and pressurize the bladder with air via the "inner tube stem" on top [which drives out a few gallons of water] to 38# of pressure before returning system to service [ 40# cut-in, 60# cut-out].

Downside would be having to replace the existing submersible pump and its starter, which still function very well...

Question: does the assembly you're describing have loss of water supply protection, such that if one's well runs dry the pump & VFD will trip o/s and self-protect? Pressure switches are available in conventional systems to afford this protection, and I know because we had one in our rural water supply system two houses ago; there's a little lever on the side of the pressure switch that must be manually lifted when initially placing the system i/s. Once pressure is established "seal-in" occurs, and the system operates automatically unless pressure drops below a certain threshold, at which point the pump trips off and stays off until manually re-started.

CR

"As iron sharpens iron, so one person sharpens another." [Proverbs 27:17, NIV]

RE: Water pressure boost pump

(OP)
Hi Keith, ok, I'll have a look if you can find a name for it. I've just been given a couple of weeks grace, so have time for research.

Failing that I think we are gently coming to the conclusion that putting the pump near the tank, where it is guaranteed 1-3m of head, would work, and a pressure tank by the house to damp things out, (thanks Bill) is a possible solution. But I'm still trying to wrap my head around the pump location.

Cheers

Greg Locock


New here? Try reading these, they might help FAQ731-376: Eng-Tips.com Forum Policies http://eng-tips.com/market.cfm?

RE: Water pressure boost pump

A lot of the small pumps are for shallow well service and will pull a partial vacuum.
Check the specs. You may not need to worry about positive suction pressure depending on your choice of pump.

Bill
--------------------
"Why not the best?"
Jimmy Carter

RE: Water pressure boost pump

I'm on it Greg and Shears! 2AM now I'll ask him tomorrow. I thought he sent me the data sheet a year ago but @#$(@^ it I can find it.

crshears; I'm not sure on the protection but 'well' find out. He explained it to me in great detail about 3 years ago but I'm on municipal water not using one, so I've forgotten those fine details.

Standby.

Keith Cress
kcress - http://www.flaminsystems.com

RE: Water pressure boost pump

Ah, I found it.
Grundfos SCALA-2

Grundfos apparently makes three different systems to 'boost pressure'.
They all have run-dry protection as one of the first 'features' (Shears).
They also seem to have 200+V 50Hz and 60Hz and 120V so I suspect they're all over the world.

1) Is the MQ3 series of booster pumps. I'm not sure they're adjustable. I believe they boost 45psi and if you want less you restrict the pressure into the pump.

Home Despot

2) The Scala-2 mentioned above. Fully settable.

3) They sell a strange pump that's long and skinny and plumbs inline with a controller mounted nearby. It appears to be pretty high-end with an insane price tag.
BMQE

Keith Cress
kcress - http://www.flaminsystems.com

RE: Water pressure boost pump

The SCALA-2 looks good with one big BUT;
From the information and the performance graphs it looks as if it runs continuously.
This may be poor documentation or I may have misread something.
Continuous running may not be the first choice for an off the grid installation.
If this unt may be set for on-demand running it may be a good choice.
Nice research Keith.

Bill
--------------------
"Why not the best?"
Jimmy Carter

RE: Water pressure boost pump

If you download the installation and operation guide, it has more complete specifications and indicates that the pump motor will stop and the standby power consumption is 2W.

I've been following this thread with interest as my cabin has only cold running water from a tank on the roof. Several family members have expressed the desire for hot water which would require a higher pressure source. We have very limited electricity from a single solar panel, two 6V batteries and a 300W inverter. This looks like it would fit the bill except I would need a bigger inverter. Grundfos has quite a few other models, I'm going to see if they have something with lower power consumption.

----------------------------------------

The Help for this program was created in Windows Help format, which depends on a feature that isn't included in this version of Windows.

RE: Water pressure boost pump

" Several family members have expressed the desire for hot water which would require a higher pressure source."

Why higher pressure?

RE: Water pressure boost pump

The current cold water system supplies 2 sinks with about 4-5 feet of head. That's adequate for hand washing or filling a kettle. The reason for hot water is to shower which would only have 1-2 feet of head and additional small pressure drop going through the water heater. So without a pump you would only get a trickle of hot water.

----------------------------------------

The Help for this program was created in Windows Help format, which depends on a feature that isn't included in this version of Windows.

RE: Water pressure boost pump

(OP)
dgallup - If you aren't worried about tedious things like safety regs you can get a smaller version of the instant hot water systems designed for 'camping'. These use D cells for the igniter, and have a lower input pressure requirement. They'll run just fine off a 12 V water pump, or a 120W shower booster pump. One of these would actually solve my problem, but they aren't certified for permanent domestic installation in Australia. http://www.ebay.com.au/itm/THERMOMATE-Gas-Hot-Wate...

I'd looked at Grundfos units, that works out way more expensive than a pump, pressure switch, bladder tank solution.

Cheers

Greg Locock


New here? Try reading these, they might help FAQ731-376: Eng-Tips.com Forum Policies http://eng-tips.com/market.cfm?

RE: Water pressure boost pump

I've seen those camping systems and may go that route but expect they won't last very long. However, our camp is only used 5 or 6 weeks a year and most of us bath in the lake so might be OK.

----------------------------------------

The Help for this program was created in Windows Help format, which depends on a feature that isn't included in this version of Windows.

RE: Water pressure boost pump

At one point you mentioned a pump near the tank and a pressure tank near the house.
I strongly recommend that the pump be mounted as close to the pressure tank as possible. Many commercially available packages mount the pump on the tank.
Mounting the pump a distance from the pressure tank may work out OK, but I have seen short cycling problems when there was too much friction pressure drop between the pump and the pressure tank.
Send pictures when the system is up and running.
Yours
Bill

Bill
--------------------
"Why not the best?"
Jimmy Carter

RE: Water pressure boost pump

(OP)
OK, I'll mount the bladder tank near the motor, that's easier anyway. But we still haven't resolved whether to mount the pump+bladder near the house or up the hill. I don't want to hear the pump, and I'm not bothered about detecting when it cycles generally. The reason is that the header tank holds 4 tons at most, so if we sprung a leak that's all I'd lose (we have about 40 tons . So my inclination is up the top.

Cheers

Greg Locock


New here? Try reading these, they might help FAQ731-376: Eng-Tips.com Forum Policies http://eng-tips.com/market.cfm?

RE: Water pressure boost pump

Greg: Stick with Grundfos, might cost a bit more but extremely well build and reliable - look at their website for all data you are likely to need.
This type of application is used extensively throughout SE Asia. There are cheap options available but my Grundfos has now been running 5 years without missing a beat.

I would go for Grundfos CH-PC (no tank type)comes as a complete unit, just fit it in the line near a power supply and between tank and shower water heater - enjoy long hot showers with trouble free operation.

It is a capital mistake to theorise before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts. (Sherlock Holmes - A Scandal in Bohemia.)

RE: Water pressure boost pump

Pump and tank separated by a distance will only work if the pressure switch is installed at the tank. Submersible well pumps are installed this way with the pressure sensing in the house at the tank. Being from a rural area, I've always been around well pumps and pressure tanks. Overall, the pump + pressure switch + tank setup generally works well without requiring much service. The VFD systems work well too but they are more money. My gut feeling is that the VFD system would use more energy to operate.

RE: Water pressure boost pump

Quote (LionelHutz)

Pump and tank separated by a distance will only work if the pressure switch is installed at the tank.
My background is similar to Lionels and I agree with his post.
As for a VFD, The main advantage that I see is reduced starting demands.
Other than that I have to wonder if the energy saving of a VFD will be enough to offset the losses.

I have always encountered or installed a pressure-pump, tank combination. I have not worked on a booster pump installation, with one sort of exception.
An existing system pumped water from a holding tank up hill to a disposal field on a mountain side.
There were two 15 HP pumps, one in service and the other as a backup.
A new field was built further up the mountain. A new pump was installed. The new pump was belt driven by a 30 HP motor.
The old pumps were so far up their curves at the new head that they would only deliver a trickle of grey water.
Regulations demanded a backup pumping system.
The two 15 HP pumps were connected in series and run together. This put both pumps into a healthy area of their curves and the system worked well.
Booster pumps work, but I don't have any experience with booster pumps and cannot comment on the relative merits of a booster versus a pump and tank.

Bill
--------------------
"Why not the best?"
Jimmy Carter

RE: Water pressure boost pump

Back from time off...

Thanks for the follow-up, Keith; if I ever need to replace our existing pump/tank/pressure switch system or part thereof I'll give very careful consideration to the Grundfos VFD design.

CR

"As iron sharpens iron, so one person sharpens another." [Proverbs 27:17, NIV]

RE: Water pressure boost pump

Pump and tank separated by a distance will only work if the pressure switch is installed at the tank. Submersible well pumps are installed this way with the pressure sensing in the house at the tank.

I learned this the hard way when I moved my bladder tank from the well head to inside the basement to minimize the amount and size of hardware I had to protect from freezing. Thinking I could leave the pressure switch at the well head...glasses, I had a graphic demonstration of just how well water in a long line can behave like an oscillator.

When I turned the power back on, the water movement turned into an oscillator that never stops... e.g. pump would start, and when the pressure switch shutdown the pump, the movement of the water down the 1" plastic line to the tank some 100' away kept going, dropping the pressure at the well head switch enough to turn it back on, reflected wave back down the line turned it off, on, off, on .. the oscillation never stopped.. I had installed a pressure gauge at the well head for diagnostic purposes, and it looked like the dial indicator was going to fly through the glass while the oscillation was going on.

Guess could have put a small surge bladder tank at the well head to try to fix it, but much easier to just move the pressure switch down to where the tank was located in the basement.

RE: Water pressure boost pump

Better to remove the bladder tank and pressure switch completely and use a pressure / flow sensing controller.

It is a capital mistake to theorise before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts. (Sherlock Holmes - A Scandal in Bohemia.)

RE: Water pressure boost pump

Just adding after thought, you could incorporate a bladder tank to cover the minimal draw-off of filling a glass of water etc. You need look carefully at the way it will be used and decide on the best set up.

It is a capital mistake to theorise before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts. (Sherlock Holmes - A Scandal in Bohemia.)

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