Best way to increase shower water pressure

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jrcollins

38 posts

Geek

#299155 15-Aug-2022 23:24

Looking for ideas on the best way to increase shower water pressure without upgrading to a mains pressure hot water system. The house was built in 1970 and has open-vented, low pressure hot water with pressure reducing valve. The shower is fed by an equal low pressure water supply.

Some of the suggestions I've encountered so far include:

better shower head and/or mixer
change cold water supply to mains pressure and install appropriate mixer
increase size of pipes from 15mm to 20mm
adjust pressure reducing valve and increase height of, or fit pressure relief valve to, vent pipe (not sure if this is an option given the age of the hot water cylinder)
all or some combination of the above

Scott3

3898 posts

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Lifetime subscriber

#2955091 15-Aug-2022 23:47

Your first option is going to be the cheapest and easyist

At a family members house they have extended the vent pipe & adjusted the PRV to suit to get a little more pressure. They have a wetback, so the tank needs to either be open vented, or to have a coil and open vented intermediary fluid which results in lower heat transfer. I think that house had methvan venturi taps from new.

https://www.methven.com/nz/fastflow

Another option you can use is to have a booster pump installed at after your tempering valve at the cylinder.

https://pumpsonline.co.nz/products/hot-water-booster-pump-stainless-steel

https://cdn.shopify.com/s/files/1/0483/7343/2471/files/trevoli-upa-15-10-hotwater-booster.pdf

That pump should add a few meter's head (pump curve above) to the discharge pressure of the cylinder. I wouldn't expect it to pull a vacuum on the tank, merely cover some of the head loss in pipework and through the shower head.

Bung

6325 posts

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Subscriber

#2955140 15-Aug-2022 23:58

Our last house had 2 separate low pressure tanks and 2 showers. One was equal pressure with shower head designed for low pressure not a slide hand piece. OK but only about 8lpm. Other was Methven mixer designed for mains pressure cold. That did give better pressure but limited by how much hot was available. I think increasing pipe size would just make you wait longer for hot to arrive. Trying to increase pressure on 50 year old tank is a gamble.

timmmay

20370 posts

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#2955142 16-Aug-2022 06:45

Installing a high pressure cylinder might be a decent option. If you don't need to change your taps it's just one thing to change, and it'll solve the problem in a straightforward way. We did it ten years ago, don't regret it at all. Can't say what it cost because we completely replaced the bathroom and moved the cylinder to the ceiling space.

itxtme

2102 posts

Uber Geek

#2955203 16-Aug-2022 09:56

timmmay:

Installing a high pressure cylinder might be a decent option. If you don't need to change your taps it's just one thing to change, and it'll solve the problem in a straightforward way. We did it ten years ago, don't regret it at all. Can't say what it cost because we completely replaced the bathroom and moved the cylinder to the ceiling space.

It will cost between 3.5-6k on average, agreed its worth it.

Eva888

2321 posts

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Lifetime subscriber

#2955313 16-Aug-2022 12:24

We went high pressure and the quotes were as much as $1000 difference so beware, that’s a four years ago we paid $3k.

YJ

145 posts

Master Geek

#2955335 16-Aug-2022 13:43

Maybe one of the simplest solution is to add a pump booster, but it's a little bit noisy when you are using it, you can add a wifi switch to remote control it as well.

something like this,

https://www.trademe.co.nz/a/marketplace/building-renovation/plumbing-gas/hot-water-cylinders/listing/3726773402

davecla

61 posts

Master Geek

#2959035 24-Aug-2022 21:39

+1 for a booster pump.

I put in a little one I got secondhand off TM with a pressure switch. Grundfos brand I think it was.

My shower mixer is a 70's style felton mix type. I did need to change the head/rose out to get decent flow.

Pressure is great now, not awesome, but much, much better. Pump is very quiet. You barely notice it.

elbrownos

109 posts

Master Geek

#2959043 24-Aug-2022 22:09

Low pressure systems are not that bad when they're running at the rated pressure of the cylinder (76 kPa), but a lot of them are running lower than that.

It's relatively inexpensive to change your roof vent for a relief valve so that you system is running at 76 kPa, and you get rid of the ugly pipe on your roof.

esawers

545 posts

Ultimate Geek

#2959106 24-Aug-2022 23:02

We bought an old house with a low pressure cylinder, noticed a huge pressure increase when we replaced the mains pipe from the Toby to the house (we dug the trench, plumber did the pipes). When we renovated awhile later we replaced the hot water cylinder with gas and had another big pressure increase, so much that our shower mixer now shoots up and sprays the ceiling so we had to make the holder much tighter.

jrcollins

38 posts

Geek

#2960227 27-Aug-2022 16:09

davecla:

+1 for a booster pump.

I put in a little one I got secondhand off TM with a pressure switch. Grundfos brand I think it was.

My shower mixer is a 70's style felton mix type. I did need to change the head/rose out to get decent flow.

Pressure is great now, not awesome, but much, much better. Pump is very quiet. You barely notice it.

Not sure if that's even possible or at least feasible with the current setup. The hot water pipe exists the top of cylinder then makes a 90 degree turn into the wall. The vent connects to the hot water pipe behind the wall and the pump has to be installed downstream of the vent. It could still be done of course but maybe not a very cost effective solution.

Speedy885

182 posts

Master Geek

#2960319 27-Aug-2022 22:03

Our house also built in the 70s with low pressure shower. The pressure was bullshit and getting worse over time so we ended up cleaning out the pipes with a snake and the amount of crap built up inside was insane! So much better now and didn't cost a cent.

aucklander

477 posts

Ultimate Geek

#2964626 8-Sep-2022 12:04

Not sure if that's even possible or at least feasible with the current setup. The hot water pipe exists the top of cylinder then makes a 90 degree turn into the wall. The vent connects to the hot water pipe behind the wall and the pump has to be installed downstream of the vent. It could still be done of course but maybe not a very cost effective solution.

same for me but once inside the wall the pipe actually gets under the house and from there gets back up to shower and kitchen, if that is the case then you could install the booster pump under the house. I added the pump very soon after moved into this 1980 house over 10 years ago and it is doing good job. Sensor (flow switch) is on the shower hot water feed, no need increased pressure to the kitchen.

the HWC has wetback and under no circumstance I wanted to loose that feature (free hot water all winter!) so upgrading to high pressure gets complicated and expensive, I abandoned the idea.

I was also planning to get mains hot water without replacing the HWC and it is perfectly doable I even purchased the heat exchanger but I did not managed to gather the courage to start installing it... basically when you turn hot water tap on, the flow sensor senses the flow and turns the pump on. Turn the tap off, the sensor turns the pump off. Pretty basic, right?

But now imagine this: the water from HWC gets through the pump then to a heat exchanger and back to the HWC. The other side of the HEX gets cold water (mains pressure), is heating it up using the low pressure hot water circuit then it gets to the taps as mains pressure hot water. The flow sensor is installed on the mains feed to the HEX (cold water). I have a sketch but I cannot find it right now... There is no reason why this does not work provided you get enough hot water flow through the HEX, which might be the only challenge (think that if you want to increase cold water temp from 10C to 50C through the HEX (40 deg temp change) and the hot water comes in say at 60C and leaves at 40C (20 deg temp change) then the hot water flow from the HWC needs to be twice the hot water flow you get to the taps... 40/20 = 2, and might need 25mm pipes for low pressure side not 15 or 20 and ideally to be connected directly to the HWC not to the pipes in/out of it... which is why I did not end up actually installing it... yet...