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General Plumbing and Gasfitting Talk => Ask Plumbers (Public) => Plumbing => Q & A - Water Pressure => Topic started by: THOMAS90 on September 23, 2011, 07:56:27 AM

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Title: Low hot water pressure - wetback system
Post by: THOMAS90 on September 23, 2011, 07:56:27 AM
Hi Plumbers,
I have a low pressure hot water cylinder with wetback but my hot water pressure is lousy.
Can anyone provide me with good advice on how best to fix this.
I want to retain the wetback - it's only a couple of years young!
What are options - a booster pump?
The open vent pipe is already reaching the sky & the water shoots out the exhaust when the fires cranking.
The ajax is already wound up as high as it will go before spilling.
A plumber installed parallel ajax valves but this hasn't improved anything.
Any suggestions?
I need a good plumber - I'm in Napier Hawkes Bay.
Look forward to hearing from you.

Craig
Title: Re: Low hot water pressure - wetback system
Post by: integrated on September 23, 2011, 07:41:49 PM
Hi Plumbers,
I have a low pressure hot water cylinder with wetback but my hot water pressure is lousy.
Can anyone provide me with good advice on how best to fix this.
I want to retain the wetback - it's only a couple of years young!
What are options - a booster pump?
The open vent pipe is already reaching the sky & the water shoots out the exhaust when the fires cranking.
The ajax is already wound up as high as it will go before spilling.
A plumber installed parallel ajax valves but this hasn't improved anything.
Any suggestions?
I need a good plumber - I'm in Napier Hawkes Bay.
Look forward to hearing from you.

Craig


Hi craig, parallel ajax valves wont do anything for pressure - it allows increased flow in times of simultaneous/multiple hot water draw-off from fixtures

you have three options - you mentioned two

1/ increase exhaust height, go to a 7.6m prv = cheapest option
2/ install hot water booster pump - this should be installed AFTER tempering valve = mid point cost wise
3/ change to mains pressure HWC with wet back coil = most expensive option

cheers
Title: Re: Low hot water pressure - wetback system
Post by: THOMAS90 on September 26, 2011, 06:13:07 PM
Hi,
Thanks for the feedback.
The wetback & cylinder exhaust are pretty tall already but certainly not 7.6m - is this measured from the top of the cylinder or from the ajax valve? I'm guessing the ajax since this is the point of pressure reduction.
If I increase the size of the pipe from from the tempering valve through to the shower from 15mm-20mm, I'm guessing I'll get more flow, but no increase in pressure - so probably no benefit? What's the pros call on this?
Thanks,

Craig
Title: Re: Low hot water pressure - wetback system
Post by: spud on September 26, 2011, 06:56:57 PM
Get rid of your tempering valve.
Title: Re: Low hot water pressure - wetback system
Post by: roberto on September 26, 2011, 09:26:17 PM
be wary of removing your tempering valve, if anyone gets burnt by the hot water temp you could be responsible for their injuries,

Here in chch, if we are the last plumber/tradesman to work on a hot water cylinder with a wetback, (even if its just to replace a pressure reducing valve washer) and we notice there is no tempering valve, and do nothing about it, and someone gets burnt/injured - we are 100% responsible for not installing one - as it is a safety device and could face prosecution.
Title: Re: Low hot water pressure - wetback system
Post by: robbo on September 26, 2011, 10:08:27 PM
hi guys/roberto, i don`t believe that is true where is that written? can you produce the reg or paper that states what you are saying,cheers
Title: Re: Low hot water pressure - wetback system
Post by: spud on September 26, 2011, 10:31:29 PM
That is total crap
Title: Re: Low hot water pressure - wetback system
Post by: spud on September 26, 2011, 10:35:32 PM
Hi I'm here to put a washer on your orb but I've noticed you don't have a tempering valve. I'm going to have to put one in and it's going to cost you $400.

But I don't have $400

I'm sorry but I legally have to install one. Go get your cheque book.

Get out of my house

I'm sorry but I'm installing a tempering valve.

I don't want one get out.

I'm putting one in get out of my way

I'm calling the police
Title: Re: Low hot water pressure - wetback system
Post by: spud on September 26, 2011, 10:37:21 PM
That's meant to be prv not orb. You get the picture
Title: Re: Low hot water pressure - wetback system
Post by: Plumber on September 26, 2011, 11:17:03 PM
Have you actually ever put a gauge on the shower to see what pressure you physically have?
Title: Re: Low hot water pressure - wetback system
Post by: robbo on September 27, 2011, 07:57:34 AM
hi guys, this is the only info that i have on Temp valves don`t know if regs have changed but perhaps others could post updated if available,cheers

When are tempering valves needed:
* When a new solid fuel heater with a wet back is fitted.
* A new (not replacement) wet back fitted to an existing solid fuel heater.
* When an additional personal hygiene fixture is installed (i.e. shower unit). In this instance it is only
the new fixture that needs to be tempered but it is easier to temper all the fixtures.
* An owner wants to change the use of an existing building from private dwelling to early childcare
or retirement home.
* Any new hot water cylinders that supply personal hygiene fixtures or appliances (not direct
replacements).
* Bathroom alterations where personal hygiene fixtures are being shifted to new positions.
Please check with your local City Council / Building Authority for final confirmation.
Title: Re: Low hot water pressure - wetback system
Post by: TNS on September 27, 2011, 08:46:55 AM
It is a bit silly to suggest removing a safety device and performing an illegal practice, so don't remove the TLV.

HWC's usually have a pressure rating, so the height of the exhaust should be from the base of the HWC.

You cant increase the hot water pressure more than the HWC pressure rating.

A TLV installed at the lowest point as possible increases the performance of the valve i.e. the lower it is installed, the more pressure there is to force water though it.

There are a few different shower roses/hoses that perform better under low pressure than others, shop around.

If any of this helps, good luck,,,, it its crap, let me know.
Title: Re: Low hot water pressure - wetback system
Post by: spud on September 27, 2011, 12:18:49 PM
Are you guys actually taking this seriously? Dam! It's actually impossible to give good advice in a forum like this. There could be any one of a hundred factors leading to bad water pressure in this instance. It's illegal for home owner to tamper with any of this sanitary plumbing installation so why not just call a registered plumber to check it out? I think that any advice given on here is encouraging illegal plumbing.
Title: Re: Low hot water pressure - wetback system
Post by: integrated on September 27, 2011, 01:19:30 PM
you're right about certain advice been illegal there A1

under health & safety act if you dont take all practicable steps to ensure safety of yourself and others you are held responsible

would it stand in court?  dont know - havent taken the risk to find out

as for where and when tlv's are req to be installed that is up to each individual T.A

imho it is good trade practice to install safety valving, E.Q straps etc on any installation if you are doing any sort of work at any particular property, im sure all would agree - 99% of the time when asked for quote etc for any work this is checked - the client/property owner is informed of dangers/hazards present and is quoted based on this

99% of clients are glad to be informed of this and much work is gained through this advice alone

as has been stated, if property has been plumbed correctly in the first place for low pressure hot water system with all valving set up properly there wont be an issue - the layman would not be able to tell it wasnt a "mains" pressure system...
Title: Re: Low hot water pressure - wetback system
Post by: spud on September 27, 2011, 01:51:32 PM
It's only illegal if you actually do it mate. My comment about t l v was tongue in cheek because the forum is absurd. We shouldn't be encouraging people to do their own plumbing or giving any kind of advice on how to. Their was a good forum on here ..... The plumbers blacklist one. Where's that gone?
Title: Re: Low hot water pressure - wetback system
Post by: integrated on September 27, 2011, 06:03:54 PM
It's only illegal if you actually do it mate. My comment about t l v was tongue in cheek because the forum is absurd. We shouldn't be encouraging people to do their own plumbing or giving any kind of advice on how to.


dont get me wrong A1 - I wasnt having a go at you, i agree with you

i realised you were taking the mickey - sometimes some things get lost in translation especially through text

and you're right - there could be any multitude of problems causing the OP's outlined situation that should be checked prior to any costly work being done
Title: Re: Low hot water pressure - wetback system
Post by: THOMAS90 on September 28, 2011, 08:30:38 AM
Spectacular - I didn't realsie that there were so many precious / anxious plumbers out there.
I'm after information so that I am informed when I engage a certified plumber to make the remedial work.
The certified plumber I engaged to install my new fire, wetback & new hot water cylinder followed the standards but didn't get the system working anywhere near to my satisfaction.
They made a crap job of installing the flue surround plate at the ceiling - cutting into the ornate cornice........I was totally pissed off.
Anyway enough said, here's my stats;

6.3m head from ajax to open vent - looks like I can get this increased a further 1.5m
flow rate measured from the bath tap - 76mL/s, I ran a 2L bottle, it filled in 26.41 secs.

What would a real plumber recommend in this situation?

1. Increase the open vent pipe to 7.6m.
2. Increase the pipe between HW cylinder & bathroom?
3. Booster pump?

Craig
Title: Re: Low hot water pressure - wetback system
Post by: integrated on September 28, 2011, 12:33:45 PM
Hi I'm here to put a washer on your orb but I've noticed you don't have a tempering valve. I'm going to have to put one in and it's going to cost you $400.

But I don't have $400

I'm sorry but I legally have to install one. Go get your cheque book.

Get out of my house

I'm sorry but I'm installing a tempering valve.

I don't want one get out.

I'm putting one in get out of my way

I'm calling the police


stil LMAO - GOLD!!


Spectacular - I didn't realsie that there were so many precious / anxious plumbers out there.
I'm after information so that I am informed when I engage a certified plumber to make the remedial work.
The certified plumber I engaged to install my new fire, wetback & new hot water cylinder followed the standards but didn't get the system working anywhere near to my satisfaction.
They made a crap job of installing the flue surround plate at the ceiling - cutting into the ornate cornice........I was totally pissed off.
Anyway enough said, here's my stats;

6.3m head from ajax to open vent - looks like I can get this increased a further 1.5m
flow rate measured from the bath tap - 76mL/s, I ran a 2L bottle, it filled in 26.41 secs.

What would a real plumber recommend in this situation?

1. Increase the open vent pipe to 7.6m.
2. Increase the pipe between HW cylinder & bathroom?
3. Booster pump?

Craig


Craig if those figures are correct then I would suggest you have issues with either the pipe - ie galv - or the pipework - ie too many bends/tees etc

could be a partial blockage somewhere?

may be easy to run dedicated line to shower/bath?

access to pipes?

lots of variables

on a low pressure system a bath should have 3/4"-20mm dia pipe as a rule of thumb, having said that 1/2" would be fine if only a short distance pipe run

for every 90deg bend (unless swept bend) or tee it is roughly equivelent in 5m worth of pipe friction, ie if water had to travel through 4 90deg fittings - bends/tees - thats the same as adding 20m of pipe length and associated pressure/flow losses due to pipe friction

I dont believe you NEED to increase vent height if prv is set right you should be fine in that regard to available pressure


I think you need to get somebody there to check it all out - let them make a judgement call - may just be easier and more cost effective to put in hot water booster pump



Title: Re: Low hot water pressure - wetback system
Post by: robbo on September 28, 2011, 02:21:04 PM
hi Thomas90,  "I didn't realise that there were so many precious / anxious plumbers out there"
 you would be precious / anxious if you had our P.G.D.Board to deal with, if you have issues talk to them,cheers
Title: Re: Low hot water pressure - wetback system
Post by: spud on September 28, 2011, 06:14:45 PM
Ha ha too right! Gotta love those informed customers who tell you how to do your job before you even start