Low Pressure Hot water Cylinder

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SRP

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#305919 13-Jun-2023 15:57

Hi Does anyone have any experience of improving the pressure or flow on a Low Pressure HW cylinder. Apparently a pump can be added to the hw pipe but do they work? Same applies to shower heads that boost flow rate. Any comments. 5k to install Mains Pressure to increase will increase my blood pressure.

Dynamic

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#3089558 13-Jun-2023 16:09

Questions:

is the pressure at the hop tap in the kitchen the same or very similar to the pressure in the shower? (A difference may indicate the shower has a flow restrictor fitted for 'hot water saving' reasons.)
How big an improvement would make a difference?
What is the 'working head' of your current cylinder? This should be on the sticker.
What is the height of the header pipe that is likely sticking out of the top of the cylinder and out the roof PLUS the height of the cylinder itself?

In my case the answers are

it is the same
any improvement would be helpful. It takes 1 minute and 15 seconds for my shower water to get to temperature
7.2m (from memory)
approx 6.5m

I wanted to fit a pressure valve to the top of the header pipe to allow me to adjust the ajax vale to give a higher head level and therefore more pressure. Plumber said I was close to my limit and this was not recommended for a 15 year old cylinder. I now live in hope that it's going to start leaking some time soon so I can justify a replacement with mains pressure.

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RunningMan

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#3089560 13-Jun-2023 16:16

Equal or unequal pressure?

tweake

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#3089561 13-Jun-2023 16:19

i have a booster pump and its ok. my shower i suspect is an all pressure unit so the pump made quite a difference. with a low pressure shower you may need to change the head to a high pressure head (smaller holes but harder spray due to higher pressure).

however the big problem was it was sucking in air via the header pipe. they fitted an over pressure valve on top, tho i'm told thats actually illegal. part of of the problem is the way the pipes are done and that the pressure regulator has trouble keeping up with the flow. part of that is due to our high water mains pressure. i fitted a primary regulator to reduce pressure for the house as its way to much which helped the hot water a bit as well.

one day i'll replace it with a mains pressure one and probably fit PV hot water system as well.

SRP

13 posts

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#3089573 13-Jun-2023 17:51

I am not sure how to reply to these individual messages if that is possible. Hope this works.

Dynamic Same or similar pressure/flow. yes mine has 7.2 head also. mI might enquire about an additional valve above cylinder but I think I am near my limit also but I am not sure - the limit of what? A 30% flow improvement would be worthwhile.

Tweake - Unequal Pressure. there nothing wrong with the cold water pressure otherwise I would have mentioned it.

Ultimate Geek. I dont think its the shower head but I could get a shower mixer that is especially designed to improve low hot water pressure flow. Greens have one called Floboost. There is another possibly Methven. It takes too long for the hot to come through to the vanity and kitchen hw taps. Tapware is a factor and very low rated water conserving taps are better as they don't restrict the flow so much.

tweake

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#3089580 13-Jun-2023 18:29

SRP: Dynamic Same or similar pressure/flow. yes mine has 7.2 head also. mI might enquire about an additional valve above cylinder but I think I am near my limit also but I am not sure - the limit of what? A 30% flow improvement would be worthwhile.

Tweake - Unequal Pressure. there nothing wrong with the cold water pressure otherwise I would have mentioned it.

Ultimate Geek. I dont think its the shower head but I could get a shower mixer that is especially designed to improve low hot water pressure flow. Greens have one called Floboost. There is another possibly Methven. It takes too long for the hot to come through to the vanity and kitchen hw taps. Tapware is a factor and very low rated water conserving taps are better as they don't restrict the flow so much.

you can get unequal flow mixers, methven makes one. but thats only good if you can change the mixer without destroying the shower.

low pressure shower heads usually flow more to get a decent shower. high pressure shower heads flow less, trade flow for pressure.

cold pressure might be issue, and i say might, and its a case of it being to good. its complicated there is many factors at play.

your basically trying to make the hot water system flow more than it was originally designed for and you may run into a few quirks. ymmv.

Hammerer

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#3089582 13-Jun-2023 18:36

We removed a cold water header tank which fed the hot water cylinder and replaced it with a pressure-reducing valve which was adjusted to the top of the low pressure range. It increased pressure 2-3 times and works great without the risks of excessive use of water and electricity and any mains pressure shock to old pipes. It has run fine since 2006.

MadEngineer

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#3089583 13-Jun-2023 18:46

Replace the cylinder.

You're not on Atlantis anymore, Duncan Idaho.

SRP

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#3089591 13-Jun-2023 19:15

@uber geek.
Change it to what?

Bung

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#3089607 13-Jun-2023 19:45

If you mean MadEngineer he means a high blood pressure tank that you are trying to avoid.

CokemonZ

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#3089938 14-Jun-2023 10:28

About a 1.5 years ago went through this.

New shower head, fatter pipes, had 2 plumbers take a look and tweak things. Nothing made a material difference.

Gave up and replaced the cylinder in the end. Life changing - recommended.

Don't spend the money on interim solutions like I did - probably $700 wasted before I made the big call.

timmmay

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#3089942 14-Jun-2023 10:45

We replaced our low pressure cylinder with high pressure. At the same time we relocated the cylinder and replaced most of the bathroom including the piping. It was night and day, going from a 70s low pressure system to a modern system, so much better. Go high pressure.

rscole86

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#3089943 14-Jun-2023 10:45

My low pressure cylinder died on its 26th birthday.

I never investigated the options for improving the pressure on our unequal system.

Had a new stainless steel cylinder installed, 180L for a family of 2.5. We've put it outside, as the existing plumbing was unsuitable for the emergency relief valves, it was only 15mm and needed to be 20mm.

I'm waiting for the invoice, but was verbally quoted 3.5-4k.

If your existing cylinder is over ten years old, then I'd go mains, as at a guesstimate 10-20% of your cost could be spent on a short term solution. Which might only been good for a day/week/year/decade, it's not a gamble I would want to take.
Your costs could be more if you need a plumber to do the work instead of DIY options (if there are any).

Added bonus is that the new cylinder will likely be more energy efficient.

Bung

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#3089945 14-Jun-2023 10:55

Fatter pipes just means more water to move before hot gets to shower. It can be catch 22 if you have an old cylinder (ours is 1967 ) pushing pressure up with a relief valve on the vent (so long as you don't have a wetback) could just bring on leaks.

My sister has just replaced the original LP tank installed in 94 with a high pressure tank. The LP was running at 76kPa so was OK.
I think the HP shower is over the top unless you are into being water blasted awake. There's no way the new tank will do 30 years.