It's (water) Hammer Time!

[NoDisplayName]

Howdy!

 

I've recently repaired my el cheapo house water pump by re-inflating the air pocket in the bladder of the  2-liter pressure reservoir tank.  Pump is now working fine, but I've now got a water hammer problem.

 

This is most noticeable when the toilet tank is refilling, causing the pump to on/off cycle continuously.  As toilet tank slowly pulls water, pressure drops in the reservoir, pump switches on and runs for a couple of seconds to bring the pressure back up, then switches off.  At that point, I get a shock wave that runs thru the pipe back to the 700-liter water supply tank and "boom!"  This repeats until the toilet tank is filled.  That can't be good for the pipes or the pump innards.

 

I've checked the YouTube videos, but most are concerned with water hammer inside the house causing pipes to rattle, not applicable to my situation.  I'm still researching, looking for a solution.

 

Any advice? 

 

What if I spliced a 3-way coupling into the pipe between the water tank and the pump, then put a short (20cm?) PVC pipe vertically, capped to hold an air pocket to absorb the reverse pressure?  Or would that simply get blown off?

 

 

 

 

[retarius]

I would use the proper sized pump for the job. I had a similar problem on our second story, a more powerful and not so cheapo pump sorted it.

[Will B Good]

Sounds like a faulty pressure switch....it shouldn't be switching off if there is still a demand for water as the downstream side will be at a lower pressure and should keep the valve open and the pump running.

 

We get this happen if the small outside shower, which is very slow, is being used because the pressure valve thinks we don't want water....ie the back pressure from the small shower is enough to trigger the pressure valve to close.

 

Does that make sebse?

[Crossy]

When you pumped up the pressure tank did you take it off the pump to ensure there was no water inside?

 

Short-cycling as you describe is often a flooded pressure tank.

[degrub]

Is there any sort of recirculation line after the discharge of the pump back to the supply tank ?

[NanLaew]

32 minutes ago, degrub said:

Is there any sort of recirculation line after the discharge of the pump back to the supply tank ?

 

recirculation line? does this bit of previously unheard of plumbing even exist here?

[NoDisplayName]

 

2 hours ago, retarius said:

I would use the proper sized pump for the job. I had a similar problem on our second story, a more powerful and not so cheapo pump sorted it.

 

This is a 250W household pump (POLO brand) put in less than three years ago by previous owner.  Costs around 2500 baht at homepro.  One story house, 700L supply tank, two occupants.

 

1 hour ago, Will B Good said:

.it shouldn't be switching off if there is still a demand for water as the downstream side will be at a lower pressure and should keep the valve open and the pump running.

 

It's switching off when the water demand stops.  This happens when the toilet tank fills, drawing down pressure from the 2-liter tank attached to the pump.  The pump fills the reservoir can faster than the toilet refills.  Draw down, refill, boom, draw down, refill, boom.  No problem during showers with constant demand.

 

1 hour ago, Crossy said:

When you pumped up the pressure tank did you take it off the pump to ensure there was no water inside?

 

Yes.  Removed, emptied completely, cleaned, pumped up to recommended 1 bar.

 

1 hour ago, degrub said:

Is there any sort of recirculation line after the discharge of the pump back to the supply tank ?

 

No.  One pipe in from supply tank to pump, one pipe out to house.  There is an additional branch from mains directly to house so low-pressure water from village or city can bypass the pump.

 

I'm hoping to get this to work for another year or so as there are so many more upgrades to the house required.

 

Just yesterday I re-piped the connections coming from the village water and from the city water.  Seems the last engineer that lived here connected the city water system and the village water system outside the wall, into one pipe coming over the wall to a single shutoff valve.  No check valves.  If both city and village meter valves were on, higher pressure city water would flow into the village line, running the water meter backwards. 

 

Planning to replace the POLO pump with a Mitsubishi or Hitachi in the fall. 

[Crossy]

1 minute ago, NoDisplayName said:

house so low-pressure water from village or city can bypass the pump

 

If this has a one-way valve then they can go leaky, not your current problem, but worth checking if you get occasional pump runs when there's no water usage.

 

We had a similar pump and the bladder in the tank went leaky, you could pump it up but after a few days it was short-cycling again. Solution was a new tank.

[Will B Good]

18 minutes ago, Crossy said:

 

If this has a one-way valve then they can go leaky, not your current problem, but worth checking if you get occasional pump runs when there's no water usage.

 

We had a similar pump and the bladder in the tank went leaky, you could pump it up but after a few days it was short-cycling again. Solution was a new tank.

Where does the water leak to.....or does it just leak passed the bladder? 

[Crossy]

1 minute ago, Will B Good said:

Where does the water leak to.....or does it just leak passed the bladder? 

 

It just goes past the bladder, the air it replaces goes up the water pipe totally invisible to the user as it's a tiny quantity.

[sometimewoodworker]

29 minutes ago, NoDisplayName said:

Seems the last engineer that lived here connected the city water system and the village water system outside the wall, into one pipe coming over the wall to a single shutoff valve.  No check valves.  If both city and village meter valves were on, higher pressure city water would flow into the village line, running the water meter backwards. 

That is a situation that neither the city water or village water supply services are going to be happy with, it is quite likely that they both have regulations that prohibit back feeding and probably could cut off service. 
I would urgently put in 2 NVRs to avoid problems. It maybe that you don’t have access to the pipework if so you should contact both suppliers to get it fixed.

 

Your explanation of the way the pipe runs will not allow your meter to run backwards. If your meter can run backwards then you have not given a correct explanation of the system.

[Crossy]

This ^^^ is where even a simple sketch is worth at least a few dozen words.

 

[Woof999]

A new equivalent pump is only 2500 baht and you're dwelling on a fix even after you know the associated pipework might be under strain?

 

I know we need to watch our pennies at times, but wouldn't a like for like replacement be the simplest (and perhaps cheapest even over the short term) solution?

[NoDisplayName]

3 hours ago, Crossy said:

 

If this has a one-way valve then they can go leaky, not your current problem, but worth checking if you get occasional pump runs when there's no water usage.

 

We had a similar pump and the bladder in the tank went leaky, you could pump it up but after a few days it was short-cycling again. Solution was a new tank.

 

Mains water goes via 1/2" pipe into the top of the tank.  Down at the ground at the base of the tank, there is a T which branches and joins the input pipe going into the house (after the water pump).  This has a PVC ball valve, closed.  Should have no effect on the system currently.

 

I haven't checked the bladder since adding pressure.  The pump seems to be working correctly, refilling the 2-liter pressure reservoir as needed.  Previously, the pump was constantly switching on/off (ticking sound) when water was drawn.......which I originally thought was the pumping noise from a cheap pump, but was the pump switching on/off a couple times a second.  Now it runs to fill the little tank, then switches off, followed by the "boom."

 

 

[NoDisplayName]

2 hours ago, sometimewoodworker said:

That is a situation that neither the city water or village water supply services are going to be happy with, it is quite likely that they both have regulations that prohibit back feeding and probably could cut off service. 
I would urgently put in 2 NVRs to avoid problems. It maybe that you don’t have access to the pipework if so you should contact both suppliers to get it fixed.

 

Your explanation of the way the pipe runs will not allow your meter to run backwards. If your meter can run backwards then you have not given a correct explanation of the system.

 

We know that now.  As i surveyed the current system, and started digging, I found that in the soi, water pipe from city and water pipe from village were joined at a T-junction, from there a single pipe came onto our property with (of course) one ball valve to rule them all.

 

Honeybunny called city and village to inquire whether the meters had integrated check valves.  No, they do not, and they informed us that the piping we had was not approved.

 

Yesterday, i dug up the pipes, added check valves at the meters, cut out the T-junction, ran two separate pipes onto our property to a mixing station with two ball-valve shut-offs leading to a T-junction.  Now we can leave both meter valves on outside in the soi, and select which water source from inside the property.

 

Interestingly, there was an old valve in the city line, underground just ahead of the T-junction, that was heavily corroded and stuck in the 1/4 open (or mostly closed!) position.  That is now gone, and flow from the city line is much higher than before.

 

2 hours ago, sometimewoodworker said:

Your explanation of the way the pipe runs will not allow your meter to run backwards. If your meter can run backwards then you have not given a correct explanation of the system.

 

The two systems WERE connected, with a branch running to our property.  Turn either meter valve on, and one wee tiny white spinny disc spins clockwise really fast.  (There are three discs that turn super slow with various increments inscribed next to them, and one disc with no increments that spins fast, I assume simply to indicate water flow.)

 

If both meter valves are on (with our single property main cutoff turned off), then that one disc with no increments (on the village meter) begins to spin slowly counterclockwise.  And here I assume that would indicate backflow into the village system.

 

 

[Dan O]

16 minutes ago, NoDisplayName said:

 

Mains water goes via 1/2" pipe into the top of the tank.  Down at the ground, there is a T which branches and joins the input pipe going into the house (after the water pump).  This has a PVC ball valve, closed.  Should have no effect on the system currently.

 

I haven't checked the bladder since adding pressure.  The pump seems to be working correctly, refilling the 2-liter pressure reservoir as needed.  Previously, the pump was constantly switching on/off when water was drawn.......which I originally thought was the pumping noise from a cheap pump.  Now it runs to fill the little tank, then switches off, followed by the "boom."

To answer your question on the water hammer, yes that would work. Cut in a T connector close to the end run to the water tank. On the vertical pipe make it a size larger than the water line your tapping into (example: main line to tank is 3/4" then cut in a 3/4" x 1' x 3/4" and 1" vertical pipe about 12" to 16") and put a cap on the end and its done.  You may have another issue with your pressure switchr something else  as it should still pump without cycling until the toilet tank is filled

[NoDisplayName]

7 minutes ago, Dan O said:

To answer your question on the water hammer, yes that would work. Cut in a T connector close to the end run to the water tank. On the vertical pipe make it a size larger than the water line your tapping into (example: main line to tank is 3/4" then cut in a 3/4" x 1' x 3/4" and 1" vertical pipe about 12" to 16") and put a cap on the end and its done.  You may have another issue with your pressure switchr something else  as it should still pump without cycling until the toilet tank is filled

 

That's what I wanted to hear!

 

The idea would be to cut the 1" pipe from 700-liter tank to water pump below the tank cut-off ball valve, splice in a 3-way connector, with the 3rd opening pointing upward.

 

There is a 90-degree bend there, so perhaps I should put the connector there, more in direct line with the pump.

 

Glue on a 1"-2" or 1"-3" reducer, the a 15-20cm section of either 2" or 3" pipe with an endcap.  The air chamber should compress to absorb the pressure when the pump shuts off.

 

That's the theory, anyway.

 

About the pressure switch.  The pump is constant when showering as there is enough demand to keep up with the pump.  But the toilet refills rather slowly. 

 

I'm guessing the pump fills the 2-liter reservoir tank to capacity and shuts off.  The toilet tank takes a few seconds to lower the pressure enough to cause the pump to switch on.  The pump again fills the reservoir in a few seconds, faster than the toilet can drain it, so it shuts off again for a short time.  Continues until toilet tank fills.  The water pipes are 1/2", but the refill tube in the toilet tank is the size of a drinking straw.

[NoDisplayName]

2 hours ago, Woof999 said:

A new equivalent pump is only 2500 baht and you're dwelling on a fix even after you know the associated pipework might be under strain?

 

I know we need to watch our pennies at times, but wouldn't a like for like replacement be the simplest (and perhaps cheapest even over the short term) solution?

 

Planning to eventually replace el cheapo with a better quality Hitachi or Mitsubishi, but I'd like to know where the problem actually lies.

 

At that time I want to simplify the piping and remove unnecessary bends.....replacing all the exposed piping:  mains to tank, tank to pump, pump to house.  Now it's old PVC, never painted, probably put together from leftover scrap.

 

Seems reasonable to try to figure out what's wrong with the current system first, otherwise I may simply be plugging a new pump into a defective piping system that will be replaced soon anyway.

 

 

[Wobblybob]

My Hitachi 155 xs does exactly the same on off....on off...on off, I drained some water from the bladder and replaced it and it worked fine for a few days then it started the same fault again. What I've noticed though when the tap is on and it's chugging away and I turn another tap on it runs ok. I don't want to buy a bladder if it really needs a new pump.

@NoDisplayName have you tried opening another tap/faucet when it's hammering, looking forward to hearing the outcome.👍

[NoDisplayName]

Photos of the thing.

 

Water lines in the soi.  Village water meter on the left.  Runs above ground to our perimeter wall and goes up to our shutoff valve.  At ground level at the base of the utility pole is the city water spliced in.  This is Thailand, and pointing in at least one photo is required, so.....that's the corroded valve stuck in the partially open position.  The city water meter is about 50 meters to the right. 

 

I've added a checkvalve here, cut out the splice, and run two separate lines over the wall to separate shutoff valves.

 

 

Village water meter with no check valve.  The indicated disk spins fast clockwise to indicate water flow.  With our shutoff closed, and both city and village water meter valves on, this disk spins slowly counterclockwise, probably indicating backflow.

 

With the checkvalve in place, no more backflow.

 

 

This is the water supply to the house.  When the better quality pump goes in, this will all be replaced, simplified.

 

 

 

k

[NoDisplayName]

34 minutes ago, Wobblybob said:

My Hitachi 155 xs does exactly the same on off....on off...on off, I drained some water from the bladder and replaced it and it worked fine for a few days then it started the same fault again. What I've noticed though when the tap is on and it's chugging away and I turn another tap on it runs ok. I don't want to buy a bladder if it really needs a new pump.

@NoDisplayName have you tried opening another tap/faucet when it's hammering, looking forward to hearing the outcome.👍

 

Good idea.

 

When we flush the toilet, it starts to refill.  The refill tube in the toilet tank is the width of a drinking straw, which cannot keep up with the outside pump.  Toilet takes a couple minutes to refill.  During this time the pump cycles on and off.  It refills the 2-liter reservoir and cuts off.  the toilet drains it slowly.  When the pressure drops enough, the pump comes on to refill the reservoir and cuts off.  Lather, rinse, repeat.

 

With the toilet tank filling and the cycle occurring, I open the sink faucet.  The demand from the toilet and tap together is enough to keep up with the water pump, so it runs constantly.  Then when I turn off the tap, while the toilet is still refilling, once the pressure drops, it returns to the on-off cycle.

 

That tells me the pump pressure switch is working properly.  It turns on when the low setting is reached, turns off when the high setting is achieved.  The bladder is holding pressure.  It's just that low flow conditions, like a toilet refill, cause the pump to cycle multiple times, whereas high flow conditions allow the pump to run continuously.

 

Regardless, each time the pump switches off, I get the hammer noise outside, at the tank and the piping connected to the pump.

[Woof999]

57 minutes ago, NoDisplayName said:

 

Planning to eventually replace el cheapo with a better quality Hitachi or Mitsubishi, but I'd like to know where the problem actually lies.

 

At that time I want to simplify the piping and remove unnecessary bends.....replacing all the exposed piping:  mains to tank, tank to pump, pump to house.  Now it's old PVC, never painted, probably put together from leftover scrap.

 

Seems reasonable to try to figure out what's wrong with the current system first, otherwise I may simply be plugging a new pump into a defective piping system that will be replaced soon anyway.

 

 

 

Gotya, that makes sense.

[NoDisplayName]

5 hours ago, Dan O said:

To answer your question on the water hammer, yes that would work. Cut in a T connector close to the end run to the water tank. On the vertical pipe make it a size larger than the water line your tapping into (example: main line to tank is 3/4" then cut in a 3/4" x 1' x 3/4" and 1" vertical pipe about 12" to 16") and put a cap on the end and its done.  You may have another issue with your pressure switchr something else  as it should still pump without cycling until the toilet tank is filled

 

My vegatative-watching-cartoons brain had a crazy thought.  Why make a vertical PVC column with a glued endcap that may not necessarily withstand the pressure?

 

The water pump has a screw on 2-liter pressurized water reservoir.  Why not put a 1/2" threaded brass outlet on the top of the 3-way connector, and screw on an additional reservoir there?   That would simplify the plumbing, only requiring a 3-way connector and a female threaded adapter, and be more robust.  If it doesn't work out and I want to return to the old configuration, I just need a 1/2" threaded brass plug.

 

I can buy a new pressure tank (accumulator) on Lazada for 200 baht.  Install the new one on the water pump, and use the old one as a pressure relief chamber.  I'd also have the option of varying the air pressure (if any) applied to the bladder.

 

 

https://www.lazada.co.th//products/i4963400338-s20887836648.html

 

Ordered:  198 baht.  Should arrive Monday or Tuesday.  I'll get the PVC parts this weekend.  Install should take an hour.  I'll update with photos and results.

 

 

[degrub]

Is the pump mounting plate bolted into the concrete pad or is it all just resting there held in place by the piping ?

 

Where is the bladder pressure tank ? I see the suction reservoir for priming the pump, assuming that is what the red blob is behind the pump case.

 

is this a centrifugal pump or positive displacement type ?

 

 

[NoDisplayName]

37 minutes ago, degrub said:

Is the pump mounting plate bolted into the concrete pad or is it all just resting there held in place by the piping ?

 

Where is the bladder pressure tank ? I see the suction reservoir for priming the pump, assuming that is what the red blob is behind the pump case.

 

is this a centrifugal pump or positive displacement type ?

 

 

 

It's a POLO brand PS-130 auto.  Same model sold under various brand names.

https://www.alibaba.com/product-detail/PS130-PS126-Series-Self-peripheral-Automatic_60722293097.html

 

The priming inlet is under the black knob at the top front.

The red blob is the 2-liter accumulator/pressure tank.

 

The pump has four bolts running through a metal baseplate, thru a thin concrete cinderblock into the concrete pad.  It feels solid.

 

 

[sometimewoodworker]

11 hours ago, NoDisplayName said:

The two systems WERE connected, with a branch running to our property. 

That (like the pipe work shown) was completely wrong

 

10 hours ago, NoDisplayName said:

At that time I want to simplify the piping and remove unnecessary bends.....replacing all the exposed piping: 

Excellent plan

 

11 hours ago, NoDisplayName said:

Glue on a 1"-2" or 1"-3" reducer, the a 15-20cm section of either 2" or 3" pipe with an endcap.  The air chamber should compress to absorb the pressure when the pump shuts off.

The larger the section of blocked vertical pipe the more effective it is likely to be. However attach it with a screw fitting not glue and the same for the end cap. The reason being that if you use screw fitting you can easily substitute a taller/shorter section of pipe, this will allow you to disrupt any harmonic that you may, inadvertently, introduce into the system. If you don’t do that you may just amplify the hammer not eliminate it.

 

10 hours ago, NoDisplayName said:

Village water meter with no check valve. 

No water meters sold in Thailand have a check valve.

 

10 hours ago, NoDisplayName said:

With our shutoff closed, and both city and village water meter valves on, this disk spins slowly counterclockwise, probably indicating backflow.

Definitely showing back flow and definitely wrongly plumbed.

 

10 hours ago, NoDisplayName said:

With the checkvalve in place, no more backflow.

That is better, and possibly good enough, the correct plumbing will allow both supplies to independently fill the tank but neither supply to directly connect to the other. The problem with that is you need 2 separate feeds (with float valves) into the top of your tank and you may not have the required inlet ports built into the tank.

[Dan O]

9 hours ago, NoDisplayName said:

 

My vegatative-watching-cartoons brain had a crazy thought.  Why make a vertical PVC column with a glued endcap that may not necessarily withstand the pressure?

 

The water pump has a screw on 2-liter pressurized water reservoir.  Why not put a 1/2" threaded brass outlet on the top of the 3-way connector, and screw on an additional reservoir there?   That would simplify the plumbing, only requiring a 3-way connector and a female threaded adapter, and be more robust.  If it doesn't work out and I want to return to the old configuration, I just need a 1/2" threaded brass plug.

 

I can buy a new pressure tank (accumulator) on Lazada for 200 baht.  Install the new one on the water pump, and use the old one as a pressure relief chamber.  I'd also have the option of varying the air pressure (if any) applied to the bladder.

 

 

https://www.lazada.co.th//products/i4963400338-s20887836648.html

 

Ordered:  198 baht.  Should arrive Monday or Tuesday.  I'll get the PVC parts this weekend.  Install should take an hour.  I'll update with photos and results.

 

 

That's a bit of overkill as the pressure isn't high enough to blow off a glued cap or you'd have broken pipes constantly now. You can do it any way you like that makes you comfortable. 

[NoDisplayName]

4 hours ago, sometimewoodworker said:

That is better, and possibly good enough, the correct plumbing will allow both supplies to independently fill the tank but neither supply to directly connect to the other. The problem with that is you need 2 separate feeds (with float valves) into the top of your tank and you may not have the required inlet ports built into the tank.

 

I brought two pipes onto the property, one for each water system.  Mounted a resin board on the wall.  Each pipe has it's own ball valve shut-off.  After the ball valves they come to a T-junction, feeding into the one pipe that supplies the supply tank.

 

Only one ball valve will be opened at any given time.  When switching water suppliers, off one first, and then on the other. 

 

Regardless, we now have check-valves at both water meters.  In theory, we could leave both open all the time, but we'll stick with only one open.

 

5 hours ago, sometimewoodworker said:

The larger the section of blocked vertical pipe the more effective it is likely to be. However attach it with a screw fitting not glue and the same for the end cap

 

Wondering if the internal diameter of the screwed fitting is important.  Feed pipe from tank to pump I believe is 1-1/2".  Upper section would be either 3" PVC column or screw on accumulator same as the red one on the water pump.  In the latter case, it's a 1/2" metal threaded fitting. 

 

Do I need a larger diameter opening for the water to surge through?  It's that as opposed to pushing 1-2 meters (with 90-degree bend and ball valve) back to the water tank.

 

And where is the most appropriate location for the pressure relief?  I would suspect as close as possible to the water pump.

 

Note this will be a temporary fix.  When we buy the new pump, I'll drain and clean the water tank, and position both tank and pump to shorten the pipes and to eliminate 90-degree bends.  Will probably also hire someone to go under the house and replace the PVC pipes there, as well.

 

 

[NoDisplayName]

3 hours ago, Dan O said:

That's a bit of overkill as the pressure isn't high enough to blow off a glued cap or you'd have broken pipes constantly now. You can do it any way you like that makes you comfortable. 

 

It does seem simpler to have a single threaded unit, rather than cutting and pasting PVC parts.  And the car-tire inflation valve on the tip allows for changing the pressure in the chamber.  That might be useful.

[sometimewoodworker]

28 minutes ago, NoDisplayName said:

I brought two pipes onto the property, one for each water system.  Mounted a resin board on the wall.  Each pipe has it's own ball valve shut-off.  After the ball valves they come to a T-junction, feeding into the one pipe that supplies the supply tank.

 

Only one ball valve will be opened at any given time.  When switching water suppliers, off one first, and then on the other. 

As I said, that certainly is not ideal as there should be no connection between the 2 supplies, but TIT and the check valves, if correct positioned, are going to reduce or stop the flow between them so if you can’t plumb them to individually feed into the storage tank it’s a bodge, but a reasonably competent bodge

34 minutes ago, NoDisplayName said:

Wondering if the internal diameter of the screwed fitting is important. 

Not very, but a very small one like ½” would not be very good 

37 minutes ago, NoDisplayName said:

Do I need a larger diameter opening for the water to surge through?  It's that as opposed to pushing 1-2 meters (with 90-degree bend and ball valve) back to the water tank.

Again the exact size isn’t critical, but I wouldn’t go smaller than 1”

39 minutes ago, NoDisplayName said:

And where is the most appropriate location for the pressure relief?  I would suspect as close as possible to the water pump.

You have lost me. What pressure relief?