It's (water) Hammer Time!

[sometimewoodworker]

Just one point. Use the largest convenient size of pipe as much as possible and only reduce the size to ½” at the outlets. You will reduce friction loss to a minimum that way.
 

FWIW our plumbing is all 32mm until the outlets, this means that when there is a power cut we can still shower as even though the pressure is reduced from 4 bar to 0.8 bar we still have enough flow.

[brianthainess]

I have a good biggish pump, and even from new as the toilet fills yes it goes on and off, its perfectly normal IMO as there is enough pressure to start filling then the pressure drops so the pump kicks in and out to keep a regular pressure. On all other taps it runs constantly.

[NoDisplayName]

3 hours ago, sometimewoodworker said:

You have lost me. What pressure relief?

 

The PVC air chamber being spliced into the feed line running from the tank to the pump.  I assume that should be spliced in as close as possible to the pump. 

 

Not sure what the exact terminology should be.

Shock absorber?  Stress dampener?  Hammerhead?  Hammerlock? NoBoomBox?

 

 

[NoDisplayName]

3 hours ago, sometimewoodworker said:

Just one point. Use the largest convenient size of pipe as much as possible and only reduce the size to ½” at the outlets. You will reduce friction loss to a minimum that way.
 

FWIW our plumbing is all 32mm until the outlets, this means that when there is a power cut we can still shower as even though the pressure is reduced from 4 bar to 0.8 bar we still have enough flow.

 

That makes sense.  When we switch pumps, we might replace the 1/2" PVC running under the house.  We could replace it all with 1" pipe from the pump to the branches.  1/2" pipe runs inside the brick walls to outlets, and will remain in place.  Outlets in the walls are 1/2" PVC fittings, not brass or steel.

 

I did check the pump bypass yesterday.  Switching the valves to have mains water directly into the house, plenty of water at the taps, and enough to have a cold shower.  Not enough pressure to reliably run the on-demand water heater.

[sometimewoodworker]

2 hours ago, NoDisplayName said:

That makes sense.  When we switch pumps, we might replace the 1/2" PVC running under the house.  We could replace it all with 1" pipe from the pump to the branches.  1/2" pipe runs inside the brick walls to outlets, and will remain in place.  Outlets in the walls are 1/2" PVC fittings, not brass or steel.

It makes sense to go up to 1½” wherever possible as that is the point at which friction losses become negligible, the difference between 1½” and ½ is about 80X less, this is also why you should go back up even if you have to use a smaller section or valve.
 

Naturally you will not want to change the pipe in the walls but everything else will help.

 

FWIW SWMBO waters the garden and we had a 1” 50 meter pipe that got old and needed replacing, she was insisting on getting another 1” pipe but after almost fighting allowed me to get a 1½” pipe the change cut the amount of time needed by about 50%, sometimes she now believes that I do actually know what I talk about. 

[NoDisplayName]

Howdy, y'all!

 

I ordered a replacement air pressure tank for the water pump on Lazada.  Set to correct pressure at the factory, with fresh diaphram, seems to help quite a bit.  Pump is running better with fewer start/stops, and the water hammer effect is much lighter.  Pump is directly beneath a window, can barely hear the water hammer thud.  Have to concentrate to hear it.  With AC on, don't hear it at all.

 

That's surprising, as I thought the problem was at the pump intake side.  But I have no experience with water pumps, and this amount of water hammer might be normal with a 2000-baht pump.

 

In the meantime, I collected the necessaries to build a water hammer arrester if needed.  1" feed pipe, with 2" air chamber above.

 

 

Screws off at the base, so could simply put the old air pressure tank there, as well.

 

[sometimewoodworker]

14 hours ago, NoDisplayName said:

In the meantime, I collected the necessaries to build a water hammer arrester if needed.  1" feed pipe, with 2" air chamber above.

That looks like it will help.
 

I would build a second set of pipe and connections that you can swap in but make them 1.7 times the hight. The reason for that measurement is so that at least one of the 2 is likely to have a volume that will not have a harmonic so will be much more effective. It is also easy and cheap to do.

[NoDisplayName]

The problem has unexpectedly resolved itself.

 

Previously, the village water had a higher flow/pressure than the city water.  Assumed that was because we were at the end of the city line.  That is not the case.

 

When digging up the lines outside the wall, we found a metal shut-off valve on the city line, just before it spliced into the village water.  That valve was heavily corroded and stuck at about 3/4 closed.

 

 

Now with a direct line from the city, bypassing the pump, we have enough pressure to operate the on-demand water heaters.

 

I was about to switch over to village water to see if we're getting higher pressure/flow from that system now, but both the city and village have just shut off water for this area, unannounced.

 

We still have the water pump connected, so can pull water from the storage tank when needed.  We'll probably re-plumb so the pump can be set to send water out to the garden faucets.  We can use that for tree-watering and keep the water in the tank fresh.

[NoDisplayName]

In the meantime, we did install the water hammer arrester v1.0 using the pressure tank from the water pump.

 

While doing so we found that the pump was NOT bolted down as we thought.  There were bolts, but only to the metal base plate.  New bolts added.

 

I also cut and capped a PVC line allowing the pump to pull directly from the mains.

 

This appears to reduce the water hammer by half.  There is still some hammer noise, but it can't be heard from inside the house.  I don't know if this is normal for el cheapo pumps.  Since we're now not using the pump, I won't bother trying to adjust air pressure or experimenting with the arrester v1.2