# Forum Home Renovation Plumbing  Domestic Mains Water Pressure High? - 850 Kpa

## Gooner

I have suspected for a little while whether my mains water pressure is a little high. The cold water gushes out of our tap and our water hammer problem has not been rectified through the installation of several water hammer arrestors and ensuring that the pipes are properly cliped to joists. 
We live at the bottom of a gentle hill and so I started thinking that this could be causing higher than avergae water pressure. I decided to grab a pressure gauge today to test it. Turns out our water pressure is 850 Kpa (8.5 bar). 
I assume this is a little high. I have read that the code states that pressure should be limited to 500Kpa. 
Should I get a pressure limiting valve installed near the mains? Is 850 Kpa excessive?

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## wonderplumb

Yes you should have a PLV installed at the water meter and you are correct in reading that the maximum pressure at any out let should be limited to 500kPa. Not only that 
but your 850kPa will almost certainly void any warranty on your appliances such as dishwashers, HWS, washing machines, ice making fridges etc.

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## Gooner

Thanks Wonderplumb for your response. 
Is it usual for a domestic water supply to be this high? Seems quite excesive. Was thinking of getting a second gauge for a "second opinion". Either way, I have suspected it is a little high for a while. 
The hot water line is running at around 4-5 bar, which seems about right.

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## wonderplumb

It isnt rare for water pressure to be this high, it also depends on where you live (in relation to sea level is a good rule of thumb) and how the reticulated service in your area is configurated, eg in Syvania waters here in sydney because its built on reclaimed land and is so flat, the water is pumped and the sewer works off a vaccuumm (spelling?) system. I once took a reading of just under 100kPa there once but usually it hovers between 700 < 850 kPa. What type of guage did you buy? The ones on a bit of hose that screw onto a hose tap are good and relatively cheap. 
You would be better off IMHO to buy a drop-tight pressure limiting valve instead of the standard ones as the normal ones work on a ratio where the good ones will give a constant 500kPa regardless of incoming pressure, unless of course the inlet pressure drops below 500. The standard ones might give you your 500kPa in an off peak period but may drop to as low as 200-250 kPa in peak demand periods which is when everyone in town is having a shower in the morning before work for example.
Bare in mind that when this valve goes in on the meter the outlet pipe work may have to be altered to cater for the extra length.

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## emptybucketman

Guys,  I think I'm experiencing a similar problem.  Where can I get one of these gauges to test the pressure?

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## wonderplumb

Reece sells them as do tradelink and the co-op, they simply screw onto your hose tap and from memory theyre about $20 or $25.

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## Gooner

Thanks again Wonderplumb for your information. 
I used a fairly good (robust) pressure gauge used where I work to test coolant pressure. Not a cheapy gauge. Don't have it on hand, but I assume it is fairly accurate. 
I bought a PLV today. It has 3 pre-set pressure settings, 350, 500 and 700kpa. I have very good under-house access and therefore was thinking of getting it installed on the 3/4" pipe entering the house. This way I am pressure limiting everything beyond the meter except the front tap. Thought I would leave this as it may be handy to have one tap with high pressure if required. 
I will have this installed and then check the water hammer situation again. (Damn flick mixers. I regret buying them. Probably more hassle then what they are worth in the long run.) If it has not fixed it, I am thinking of experimenting with an air chamfer type setup that will absorb some of the pressure shock. I have a section of 3/4" pipe that tuns out of the house where a water heater use to be. I will simply thread a pipe of 3/4" pipe pointing straight up (closed at the end and full of air) at that spot and see what effect it has on water hammer. (Water hammer suppressors are getting a little on the procey side. Especially for 3/4" piping). 
Thanks again.

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## yozza

pffffff 850kpa!!!! 
Our little town has water pressure ranging from about 1000kpa to 1200kpa.  garden hose fittings always blow off, poly pipe has a tendacy to burst in winter, but as of yet my dishwasher and washing machine have operated faultlessly for nearly 4 years.  As a member of the local CFA having such high pressure makes it very difficult when switching between water sources ie tanker tank and mains pressure.  not uncommon for us to blow hoses at fires.

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## Gooner

Yozza.. I wouldn't have noticed or cared about the water pressure being high if it wasn't for the savage water hammer caused by the flick mixers and fast-acting washing machine solenoid. 
I trottled the pressure back to 550 Kpa and the water hammer dissappeared.  
550 Kpa is plenty for domestic water supply. It's lot like we can hose down our driveways anymore.

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## Smurf

At my parents house it's over 1000 kpa. They had to put a pressure limiting valve on the inlet to the water heater otherwise the relief valve (1000 kpa) just stayed open and let all the hot water out. 
It's caused a few minor problems. The dishwasher inlet solenoid has been replaced 3 times and had one washing machine hose blow apart. And you have to turn the taps off slowly otherwise there's water hammer.  
Oh, and water timers on the garden taps had a tendency to spectacularly blow apart without warning. The best one was the fancy electronic one. It cracked overnight and a leak shorted the electronics causing it to constantly cycle on / off every few seconds. The resultant water hammer woke up everyone in the surrounding houses, one of which had to replace their water heater not long after that...   
On the good side, no need to worry about pressure washers when you've got this sort of pressure on tap. And as a child I remember quite well messing about with the hose and it was easy to send the water out the nozzle straight over the house - watering the front lawn standing out the back. It wasn't until I left home and moved out of the area that I realised that water pressure wasn't normally this high.  
And it was handy for washing down the house, cleaning out the gutters etc. No meter and no restrictions (except on total fire ban days) and it's still that way today.

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## Gooner

> The best one was the fancy electronic one. It cracked overnight and a leak shorted the electronics causing it to constantly cycle on / off every few seconds. The resultant water hammer woke up everyone in the surrounding houses, one of which had to replace their water heater not long after that...

  That's a fantastic story. 
Makes me wonder... One morning not too long ago I was woken up by a very severe "thud thud thud" water hammer type of noise in our plumbing. However, everyone was in bed so I became concerned as to why it would have occurred. Went around looking for anything suspicious but found nothing. I wonder if it was something the neighbour did and travelled through to our house?

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## Smurf

> That's a fantastic story. 
> Makes me wonder... One morning not too long ago I was woken up by a very severe "thud thud thud" water hammer type of noise in our plumbing. However, everyone was in bed so I became concerned as to why it would have occurred. Went around looking for anything suspicious but found nothing. I wonder if it was something the neighbour did and travelled through to our house?

  Sometimes you could tell when the neighbours flushed their toilet etc simply by the thumps that could be heard from the water heater which seemed to amplify the general hammer sound inside our house. 
It would work up quite a tune at times - clunk, clunk, thump, THUMP!, clunk, clunk, clunk, thump, thump... It went away eventually when a few more houses were built nearby but was like that for at least 5 years that I remember (probably closer to 10 years).

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