HELP - cold water pressure on some taps low

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xlinknz

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#320362 4-Aug-2025 20:21

Hi all

I have what seems to be an unusual issue

4 outlets (Faucets) of water downstairs in our 2 level home (shower, laundry, vanity basin and bath) have much lower cold water pressure.

notes

All these are dual hot cold water) the nearby outdoor tap is normal pressure but that tap being outdoor cannot produce hot water and is immediately adjacent to the gas instant hot water heater
We use continuous gas hot water heating
If I mix these dual faucets to include hot water pressure is normal!

Upstairs (road level) no issues with cold water pressure. I suspect the shower, laundry, vanity basin and bath downstairs are all on the same water circuit (except the outdoor tap)

What could the issue be?
Any ideas on how to resolve beyond calling a plumber?

Regards

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#3400041 4-Aug-2025 20:46

How old is the house? Our previous house was old enough to have had galvanised iron cold pipes that had almost blocked with rust. Are there flexible connectors from mixer to wall with either a stop tap or flow restrictor in line? Did you ever have a low pressure electric tank?

timmmay

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#3400044 4-Aug-2025 21:00

Have you tried turning them off and then on again? 😀😀😀

Sounds like some kind of a blockage. A plumber is probably going to be useful, particularly one with a camera. I've never had a camera in a water pipe, only a sewer... you'd probably not want the sewer camera in your water pipe...

Bung

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#3400045 4-Aug-2025 21:05

Even if there was a camera small enough to fit 15/20mm water pipe there'd be too many 90⁰ bends.

timmmay

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#3400048 4-Aug-2025 21:19

I guess that's why you need a plumber, they'd know things like that

gzt

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#3400068 5-Aug-2025 01:14

xlinknz: I have what seems to be an unusual issue

When did it start?

mdooher

Hmm, what to write...
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#3400091 5-Aug-2025 08:11

"cheap" mixers downstairs?

Matthew

wellygary

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#3400093 5-Aug-2025 08:45

gzt:
xlinknz: I have what seems to be an unusual issue

When did it start?

Yes, this,

Are you new to the house? Or has it just started happening?

The cold water feed to the Rinnai HW unit is likely straight from the house feed like (this will also likely feed the nearby outside tap),,

The interior mixer taps that are causing you concern will likely be fed separately,( hence why there is a difference in flow)

Sharesies

Trade NZ and US shares and funds with Sharesies (affiliate link).

richms

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#3400112 5-Aug-2025 10:18

The only reason I can think of for low pressure is that there was a low pressure hot water cylinder at some time, and the taps were fed from that to make the mixers work properly and whoever fitted the new hot water system never removed the old header tank or pressure regulator.

Partially clogged pipes or a blocked filter will not drop the pressure, it will just limit the flow of water, pressure will still be normal with no flow of water.

Richard rich.ms

concordnz

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#3400120 5-Aug-2025 11:04

clogged pipes & blocked filter will definitely drop the pressure.

I had this same problem till recently -

Taps inside and shower all had low pressure. but outside was good.

I thought it was due to low pressure HWC, but changing that did not fix problem, neither really did changing shower mixers.

Main water pipe in area suffers regular leaks.

and after one repair, my cold water pressure got even worse!

It was at thst point a plumber found the previous owner had installed a Filter (to protect the taps/valves from dirt/grit introduced from repeated pipe repairs

and this filter was badly blocked.

Since getting this cleaned out - my water pressure has been like Heaven!

Definitely get a plumber to check for existence of a filter and clean it out, if he finds one..

tweake

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#3400196 5-Aug-2025 18:00

first thing is it low pressure or low flow? most people get them mixed up.

when you use the down stairs tap, does using another one at the same time make it worse? if so most likely a restriction in the pipes eg crushed pipe etc. also you might notice that just as you open the tap the water flow is good, but goes bad straight away.

if its actually low pressure, it means there is a pressure regulator in the line somewhere and the cold feed is on the wrong side of it. most common place for that is hot water cylinder or where one used to be.

xlinknz

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#3400207 5-Aug-2025 19:23

Thank you all for your replies

Subsequent to the creation of this thread I remembered and rediscovered that the downstairs hot and cold water is controlled by a couple of solenoid valves (behind a closet panel)

The right hand one is the cold water and when one of the before mentioned water faucets is used on cold only I can hear (the cold one) clicking. I suspect the solenoid is stuck partially open

What I don't know yet is

Whether (brown) solenoid can be removed from its brass fitting to allow it to be checked in case it is stuck partially closed due to limescale or debris or whether the solenoid itself including brass fitting requires to be replaced in its entirety
Whether I can remove the unit partial or full without water escaping despite turning off the water supply

wellygary

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#3400222 5-Aug-2025 21:25

xlinknz:

Whether I can remove the unit partial or full without water escaping despite turning off the water supply

Turn off the water supply at the Toby, then also run the internal taps to empty most of the water -

Also First turn off the Rinnai, - the last thing you want is for it to start or try to run when there is no water feed.

gzt

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#3400223 5-Aug-2025 21:31

Is the wet site mechanically isolated from the solenoid on those things? After turning off the power source can the electrical part be removed without risk of flooding or damage.

k1w1k1d

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#3400240 5-Aug-2025 23:10

The brown square solenoids are just coils. They should have their manufacturer and voltage etc stamped on them.

Turn off the power and undo the nut on the end and slide the coil off the chrome shaft. It won't leak water.

With the water turned off and drained you should be able to remove the valve cartridge from the brass body.

Be careful not to lose, or nick, any of the rubber seals on the cartridge.

Might be an idea to call a plumber?

concordnz

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#3400310 6-Aug-2025 12:27

I think you are definitely closing in on the issue.

Why do you need the have the downstairs Water seperated/through a solinoid - that's most unusual.

especially if you have no way to trigger the solinoids manually.

I'd simply remove both solinoids from the circuit and get a plumber to join the pipes / put a short copper liner in their place = Less points of failure in the future.

If you mess around there yourself - That GIB board is going to get wet and risk turning into it's own disaster zone (get a Plumber)

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