# Forum Home Renovation Plumbing  dripping temperature/pressure relief valve

## dspence

Hello All,
I have a constantly dripping (verging on constant leaking) TP valve on my hot water heater.  
I have replaced the TP valve, and have verified that the thermostat is working and the water temperature is not crazy. I have also replaced the pressure limiter on the cold water inlet. Is still leaks, and is getting worse. 
I measured the pressure on my water supply recently - it's at 800kPa. Pretty high I think. Still, the pressure limiter on my hot water tank input is rated up to  2000KPa, and limits to 500kPa. The Pressure relief valve should open at 1000kPa.  
Should I put a pressure limiter on my entire house? The pressure is pretty crazy at all my taps. Is the heater dripping because the pressure limiter is a one-way valve? How can I stop it dripping? 
any advice welcome,
dave 
Addition...
OK after more checks I'm pretty sure I need an expansion tank after the pressure limiter, although I'm not quite sure why the tank was put in without one (it's only 5-10 years old and I suspect it breaks Oz regulations?). Should I put a limiter on my entire house and a expansion tank, or just on the hot water tank? I have no non-return valve on my house water supply. 
But...
One more piece of info. If I depressurise the tank, say by letting a large amount of water out of the TP valve, then after the tank has refilled from the inlet, the TP valve immediately starts to drip. This seems to suggest that it is dripping when the tank pressure is equal to inlet pressure...

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## SilentButDeadly

Talk to Sydney Water about your supply pressure and whether it conforms with their supply obligations under their operating licence.  Check also to see whether you are in one of the areas proposed for supply preesure management works and when that will occur.  If it's a while away then a whole of house pressure limiter would be a good idea. 
As for your HWS........something odd there for sure.  Are you sure that the TP operating specs are appropriate for your model of HWS? Apart from the above and suggesting you aquirie the services of a professional I have little advice to offer.

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## wonderplumb

What make, model and size is your HWS and is it gas or electric?

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## dspence

> What make, model and size is your HWS and is it gas or electric?

  It's a Rheem 101 series, 315 litres. Electric, only heats at nighttime on cheap rate.  
I took the tp valve off last night  - it's stuffed... i can blow through it so I'm pretty sure it's not closing properly. Do they stick open if they drip too much for too long? Still, even when it was brand new, it dripped as soon as the tank was pressurised.

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## wonderplumb

TPR valve should be rated at 1000kPa.
PL Valve could be buggered and depending on where you tested your incoming water pressure it may in fact be higher than the 800kPa you said, especially late at night when there is a very low demand on the water main pressure can rise considerably.
The way you operate the lever on your TPR valve is crucial as 99.99% of people yank it open then let it snap shut which will bugger it.

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## dspence

> TPR valve should be rated at 1000kPa.
> PL Valve could be buggered and depending on where you tested your incoming water pressure it may in fact be higher than the 800kPa you said, especially late at night when there is a very low demand on the water main pressure can rise considerably.
> The way you operate the lever on your TPR valve is crucial as 99.99% of people yank it open then let it snap shut which will bugger it.

  TPR valve is indeed 1000kPa. When I started to try to solve this about 9 months ago, I first replaced the TPR valve, and it dripped every few seconds immediately. A couple of months later I replaced the PL valve, and that made no difference. Now the TPR valve is clearly damaged... Do I replace it again??

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## wonderplumb

How much is it actually dripping? It is actually supposed to drip a little during the heating cycle, this means it is doing what its supposed to .
Stick a bucket under it and if it fills this bucket (standard household 10L bucket) in less than 24hrs there may be something more sinister afoot.
Please be sure you have infact got the right TPR valve for it, though it might be set at 1000kPa there is a few different types that are. I cant remember the exact model number for the valve. How did you identify which replacement valve to buy?

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## wonderplumb

Here we go, it should be a HT55 (1000kPa 99deg) and it must be a RMC (Reliance Manufacturing Company) valve to conform with Rheems warranty and so on and so forth. http://www.rheem.com.au/service.asp?view=d_elec#DETPRVR
And this states as I posted above..........

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## Smurf

> The way you operate the lever on your TPR valve is crucial as 99.99% of people yank it open then let it snap shut which will bugger it.

  What is the correct way? 
The one I have now doesn't have a lever, just a knob that you turn until it goes "click" and the valve snaps shut. The other one I look after, at my parents house, has the lever.

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## dspence

> Here we go, it should be a HT55 (1000kPa 99deg) and it must be a RMC (Reliance Manufacturing Company) valve to conform with Rheems warranty and so on and so forth. http://www.rheem.com.au/service.asp?view=d_elec#DETPRVR
> And this states as I posted above..........

  Yes, this is exactly what it is. When the TP valve was brand new, it was dripping at a maybe a drip per second. I thought they weren't supposed to drip at all with correct operation?

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## Smurf

> Yes, this is exactly what it is. When the TP valve was brand new, it was dripping at a maybe a drip per second. I thought they weren't supposed to drip at all with correct operation?

  Water expands when heated so the valve should drip when the water is being heated (when the element is on) and not drip when it isn't being heated.  
Without the valve or some other way to get out, the pressure build up from the water being heated would cause an explosion, hence the importance of not blocking up valves etc. 
How fast it drips when heating will depend on how fast the water is being heated. A 1.2kW element gives a slow drip, 2.4 or 3.6kW is a steady drip, drip, drip. 6kW is a fast drip. Your 315 litre tank on off-peak probably has a 3.6 or 4.8kW element.

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## dspence

> Water expands when heated so the valve should drip when the water is being heated (when the element is on) and not drip when it isn't being heated.  
> Without the valve or some other way to get out, the pressure build up from the water being heated would cause an explosion, hence the importance of not blocking up valves etc. 
> How fast it drips when heating will depend on how fast the water is being heated. A 1.2kW element gives a slow drip, 2.4 or 3.6kW is a steady drip, drip, drip. 6kW is a fast drip. Your 315 litre tank on off-peak probably has a 3.6 or 4.8kW element.

  Yes, absolutely. But it drips when the water is not being heated. It drips all the time, right from the moment I installed it.

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## bricks

Then you have too much pressure in your tank..
It is very uncommon to have 2 faulty valves in a row. (ie when you replace a faulty valve with another)

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## looseless

You definitely need to put a pressure limiting valve on your meter.  800kpa is too high for domestic water supply.  Any new residence in Vic. is required to have domestic supply at a maximum of 500 kpa.  By the time the HWS heats at night mains pressure may have increased due to reduced domestic demand and the thermal expansion of the water can mean 3-5% of the capacity of the HWS can be "bled" by the PTR valve during the heating cycle. 
As it leaks all the time the one you have got now is stuffed, so you should get a Pressure limiting valve of 350 kpa or 500 kpa installed at your water meter, before you install a new PTR valve. :2thumbsup:  :Biggrin:  :Doh:

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## dspence

> You definitely need to put a pressure limiting valve on your meter.  800kpa is too high for domestic water supply.  Any new residence in Vic. is required to have domestic supply at a maximum of 500 kpa.  By the time the HWS heats at night mains pressure may have increased due to reduced domestic demand and the thermal expansion of the water can mean 3-5% of the capacity of the HWS can be "bled" by the PTR valve during the heating cycle. 
> As it leaks all the time the one you have got now is stuffed, so you should get a Pressure limiting valve of 350 kpa or 500 kpa installed at your water meter, before you install a new PTR valve.

  Thanks. I have installed a 500kpa limiter on my house, and this will solve other house glitches like crazy taps, water hammer, and garden watering pipes breaking.  
I'll replace the TPR valve again, but there was already a 500kpa limiter on the hot water system. Unless the old limiter was broken and my new tpr valve was damaged before I replaced the limiter, I'm still not sure why i have recurring issues!

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## dspence

Thanks for the advice. The problem was high house water pressure and unfortunate order of replacing parts I think. To recap, my boiler TP valve was leaking constantly, despite having the correct valve and a 500kPa pressure limiter. House pressure was 800kPa. 
1. Replacing valve made no difference
2. Replacing tank pressure limiter a month later made no difference
3. Replacing valve again fixed problem! 
So, either the first replacement valve was broken, or the original pressure limiter was broken, and the constant overpressure on the tank broke the first replacement valve before I replaced the limiter.... 
Thanks for the advice
dave

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