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Hot Water Pressure

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  1. #1
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    Default Hot Water Pressure

    I have recently had renovations done at my house, and the hot water was converted from a Gravity feed with tank in the ceiling, to a Mains pressure Hot Water Service mounted under the house, in the same location as the old Hot Water Heater.
    the problem is the hot water pressure is no better than it ever was with teh gravity feed system, and in some rooms it is worse.

    Because it is so bad, it takes an age to heat up at the taps and continues at a very slow rate.

    I have a tempering valve installed at the cylinder, as well as shut off valve ( i dont know the proper name for it).
    i was wondering if these may be the problem, or could it be the pipes.
    Im not sure the diameter of the piping, but it was NOT replaced from teh gravity feed system, and i am dubious about the quality and diameter.
    in fact, the only NEW piping installed to a vanity in the new bathroom, has poor cold water pressure as well, and the hot at that sink is barely a trickle. all the plumber did was replace all the threaded joins with solder joins and replace the pipe from under the house up the walls to the fittings, so all the pipework behind new plaster is new for the hot and cold pipes. but under the house, he left the old copper pipes for the hot water, and galvanised pipes for cold water that he simply joined onto whereever the pipes went into the walls to fittings.

    THe builders have since stopped talking to us, and they have not paid any of their subcontractors, such as the plumber, so nobody will come back to look at it.


    i have already checked the taps mixer filters, and they are fine. the cold water pressure everywhere aside from teh vanity, is quite good, but the hot is really really slow.

    as a rough guide, Once the water is hot from the taps (which takes a good minute or so), it took about 29 seconds to fill a 1L container with pure hot water. so a flow rate oof only about 2L per minute roughly i would say. and that was at the kitchen where the flow is best.
    in the laundry, which is farther away from the HWC, it took closer to 38 secs for a 1L fillup. and the vanity takes nearly a full minute to filla Litre.

    Any advice would be welcomed, ideas on whether there is anything i can check myself, filters etc??

  2. #2
    A Member of the Holy Trinity silentC's Avatar
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    Not a plumber but I know that pressure reducing valves are now fitted to all new hot water systems.
    "I don't practice what I preach because I'm not the kind of person I'm preaching to."

  3. #3
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    I dont think mine has that. the only fittings on the outlet side is the tempering T-piece and a stop valve with a small black dial that will completely shut off the hot water supply to the house, out of the cylinder.

  4. #4
    A Member of the Holy Trinity silentC's Avatar
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    It would be on the inlet side - it's designed to stop the cylinder exploding from too high mains pressure. I have a vague recollection that there is also a pressure reduction device in the tempering valve on the outlet side too. Some little plastic thing that fits into the outlet.

    As far as I know, these things are required by law now in NSW.
    "I don't practice what I preach because I'm not the kind of person I'm preaching to."

  5. #5
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    you say you have sections of old gal pipes?, does any of this feed to the hot water system & basin? as gal rusts inside eventually to the point a drop will be lucky.
    Tempering valves do have strainers in the hot & cold inlets.
    The pipe sizing, should be ok , usually gravity fed systems are a 3/4 outlet that have 5/8 drops.
    have you checked the aerators on the sink spouts aswell, not that that will be the main prob, but if you have different pressure, you may have a few clogged aerators.

  6. #6
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    1. Have you measured the flow from a cold tap? If so, how many litres per minute?

    2. Have you checked that the inlet valve to the water heater is fully open?

    Also, does the flow drop noticeably with only a slight turn of the valve down from full? It normally shouldn't but might if the valve is a dud.

    3. I assume that the mains pressure HWS is a storage tank? Or is it instant type?

    4. If it's a storage tank, operate the relief valve (open and close it GENTLY or you'll break it). How good is the flow from the pipe coming from the valve? (Ideally measure it).

  7. #7
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    Cold Water from the kitchen tap is about 8seconds per litre, so thats about 7 - 7.5 L/minute.
    the hot is more like 2 L/minute if i am lucky.

    The inlet valve to the heater is turned open as far as the small black dial will turn, so i assume it is fully open.

    I will check the slight turn theory.

    It is a 240L storage tank. the relief valve, do you mean the lever style on the opposite side of the tank, which runs down to an overflow style pipe?

  8. #8
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    Default

    thats the one

  9. #9
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    ok, i will check that one tonight.
    it does flow a reasonable amount out of hte overflow pipe everyday, i noticed on the weekend. not a constant flow, but a fair amount of water over the day drips out onto the ground from the overflow pipe.

  10. #10
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    What I am trying to work out, by checking the relief valve maximum discharge rate when open, is whether the problem is on the inlet or outlet side of the hot water cylinder plumbing. That is, not enough can get in? Or it can get in but can't get out through the hot water pipes around the hose? Knowing that will narrow the range of possibilities as to what's wrong.

  11. #11
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    Mate if the relief valve dumps with as much or nearly as much pressure as the cold water then it may be in the HW pipework where you will find your problem.
    Plumbers were around long before Jesus was a carpenter

  12. #12
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    i havent had a chance to test this yet, but i did notice wheni moved a pile of rubbish from outside the house yesterday that the ground is VERY VERY wet and the relief valve pipe trickles almost constantly.
    should it be plumbed into a drain or something? at the moment it simply runs through the wall from under the house and drips into the dirt outside my house. for about 50cm all around, the ground is quite damp.

  13. #13
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    That would mean the reief valve needs replacing for a start.
    Plumbers were around long before Jesus was a carpenter

  14. #14
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    ok, i am getting a couple of plumbers out to give quotes to check it out and fix the hot water situation.
    we also discovered yesterday that the toilet pan is leaking, and trickling water out from underneath everytime we flush.

    This is just never ending.

    Anyy recommendations on a good plumber in Hobart, Tas?

  15. #15
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    My Hot water pressure problems are now fixed.
    Yesterday we discovered a leak around the toilet Pan, so called a plumber in to fix that.
    i mentioned to him that the hot water pressure was bad and he went under the house, saw that we had a NEFA brand Pressure Limiting Valve and said he would 99% guarantee that was the problem. He told me that about 1 in 5 of the NEFA brand valves fail and they dont use them anymore.

    so he replaced the valve, and hey presto we have pressure!!!!
    as for the vanity tap which had poor pressure on hot and cold, I removed a small O-ring from the filter on the tap and it now works perfectly!!

    Thanks to all who replied, i am releived it was something so simple and cheap to fix!!!

  16. #16
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    Not a plumber but I know that pressure reducing valves are now fitted to all new hot water systems.
    I dont think mine has that.
    "I don't practice what I preach because I'm not the kind of person I'm preaching to."

  17. #17
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    haha. thankyou for pointing out the obvious stupidity on my part!!!!

    not knowing what it looked like, i had the non return valve and pressure redcing valve all connected directly to each other, and i thought it was all one thing!!!

    As you can obviously tell, i am not a plumber either.

    Oh and by the way, the problem with the toilet pan leaking - the trap on the toilet sat about 20mm offset to the pipe through the floor, but the plumber decided he didnt need to use an offset Pan Collar, but instead stretched a rubber boot across the offset!!!! and needless to say, 3 months down the track, the boot had split, and moved and water was running everywhere.
    1 x offset pan collar later, and it is all fixed.

    I tell you what though, next time i will only go with recommended tradesmen. all of these contractors were subcontracted by the builder we hired, so we had no idea who they all were, and everyone of them has done shoddy work.

    Lesson learnt. the hard way.

  18. #18
    A Member of the Holy Trinity silentC's Avatar
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    I only knew about it because my old man is a plumber and he did the plumbing at our place (dual occupancy). He put one of those pressure limiting valves on both systems because he was told that he had to and I remember him going crook about the price of the things. The pressure in his place was lousy, so he took it off and it made all the difference. That's why I had a feeling it might be what your problem was going to be. I'll check ours because if it's one of those NEFA brand ones I'll get him to replace it.
    "I don't practice what I preach because I'm not the kind of person I'm preaching to."

  19. #19
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    When I was a boy, IIRC, they were called AJAX valves.

  20. #20
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    Quote Originally Posted by silentC View Post
    I only knew about it because my old man is a plumber and he did the plumbing at our place (dual occupancy). He put one of those pressure limiting valves on both systems because he was told that he had to and I remember him going crook about the price of the things. The pressure in his place was lousy, so he took it off and it made all the difference. That's why I had a feeling it might be what your problem was going to be. I'll check ours because if it's one of those NEFA brand ones I'll get him to replace it.
    You have to in a lot of areas these days, the trusty AS3500 states that; the maximum static pressure should not exceed 500kPa (50m head) at any outlet.........
    a lot of people have dramas with dishwashers, hot water heaters, washing machines, fridges with ice makers etc. because the manufacturer will state the maximum inlet pressure for the appliance which is usually 500kPa but fridges and icemakers are sometimes as low as 150kPa.
    People ring the manufacture saying the machines had the richard looking for a repair under warranty. They send out a technician and the first thing they do is check the inlet pressure and say "sorry mate, warranty's void" if its over their maximum stated pressure.
    Example, Sylvania Waters here in Sydney is a 'man made' series of canals and what they call islands, built on a stinking black mud mangrove swamp. Its only a small suburb but it is dead flat the whole way through, therefore their water is pumped and they are on a vacuumm sewer system. Ive taken readings of nearly 1100kPa in the dead of the day and between 600 and 800 kPa in peak periods.
    A fella I know was asked to run some water under the house and up for a new fridge with icemaker and all the gear, which cost the owner $5,500 (the fridge that is!). The instructions stated the max inlet pressure must be 350kPa or under, please use our PLV provided by us to acheive this task, (they are a little plastic unit that also acts as a check valve).
    All was well, three weeks later gets a call from the owner to get here now and meet with the technicion from the manufacture. The pressure had blown the guts out of their little valve, blew something in the back of the fridge, flooded the place and ruined the owners new hardwood floor.
    The owner put it on the manufacturer who put it on the plumber because the inlet pressure exceeded their recommended 350kPa.
    "but I used your limiting valve as per instructions" said the plumber, to which the technician replied "but the max inlet pressure to the valve has to be 500kPa or under".
    "show me where it says that" the plumber replied, and they couldnt find anywhere on the instructions or the valve that said the max inlet pressure to the valve had to be 500kPa blah blah blah.
    Long story short, the plumber seeked out advice from the master plumbers assoc., who put together a team of officials from SAI global and waterboard inspectors and went to court with the manufacturer, who was found negligent for not specifying the max pressure in their instructions etc. and had to cough up a neww hardwood floor, new kitchen as the cabinets had swelled, and new carpet for the dining room and hall.
    Plumbers were around long before Jesus was a carpenter

  21. #21
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    Quote Originally Posted by silentC View Post
    I'll check ours because if it's one of those NEFA brand ones I'll get him to replace it.
    Is NEFA not a good brand?

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