DIY Doctor

Shower hot water pressure very low even after fitting new shower

Postby webster2020 » Wed Oct 21, 2020 10:32 am

Hi

A new member and very definitely a non-expert in DIY. We had a problem with our shower, whereby the pressure on the hot water was very low, to the point where it was unusable.

We've had a plumber round to fit a new shower (hansgrohe Ecostat 1001 CL Thermostatic Exposed Bath Shower Mixer) which solved the problem for about a week. Unfortunately, the issue has now returned.

- all other taps and showers in the house are fine
- the cold water pressure on the shower is fine
- we've got a condensing boiler on the ground floor
- tank is on the top floor

A week after the new shower was installed, the hot water pressure on the shower became a dribble. Occasionally, the water 'pulses'.

I'm confused as to what might be causing the problem and after some guidance.

Many thanks.
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Postby stoneyboy » Fri Oct 23, 2020 6:54 pm

Hi webster2020
Most likely cause is that you have an airlock in the hot water supply pipe to this particular shower. Try removing the shower hose, turn the shower onto its hottest setting and turn on, this may clear the airlock.
If this fails presumably you have isolating valves next to the shower valve, turn both off, remove the shower valve then turn the hot back on. This should clear any airlock.
Regards S
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Postby webster2020 » Sat Oct 24, 2020 6:24 am

Hi

Many thanks for your reply, it’s very much appreciated.

Unfortunately the entire shower/bath area is tiled, so whilst we might have isolating valves, they’re hidden behind a wall and tiles.

When the tap/shower was fitted the plumber switched off the stopcock. I’m assuming I’d need to repeat that exercise to clear the air lock, but I’m unsure how to isolate the hot tap.

Thinking back, I seem to recall that it first started happening when the bath was being run and when the bathroom toilet was flushed.

When the plumber fitted the shower, he switched off the stopcock and opened all the taps, but didn’t touch the toilets.

I’m not sure if the extra bits of info will help, but thought it worth mentioning.

Many thanks
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Postby stoneyboy » Sat Oct 24, 2020 8:59 pm

Hi webster2020
If you are on a gravity fed hot water system this Hansgrohe valve is not suitable unless you have a pumped supply to the valve.
Regards S
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Postby webster2020 » Sun Oct 25, 2020 9:06 am

Hi StoneyBoy.

There's a hot water tank on the top floor, but no cold water tank, so I'm assuming cold water is off of the mains.

The mixer bar worked for a week without any pressure problems, the one it replaced (also a hansgrohe) only had pressure problems at the end of it's life and the other hansgrohe shower (same model) in the shower room is next to the hot water tank. It doesn't have any problems.

I'm thinking it's either; as you said, an airlock problem, some sludge or a faulty thermostatic valve in the bar. Given it's a new unit, we'd have to be unlucky with a faulty thermostatic valve.

What I can't work out is why it worked for a week and then had problems.
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Postby stoneyboy » Sun Oct 25, 2020 9:39 pm

Hi webster2020
I assume that the hot water only trickles out of the spout when the valve is set to tap mode. If this is the case then first thing is to check the filter which is fitted to the valve.
Regards s
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Postby webster2020 » Tue Oct 27, 2020 1:19 pm

Hi.

You’re correct the water was only trickling out when in tap mode and when the temp was high. The lower the temp went, the higher the pressure went. This was also the same experience when using the shower attachment, ie low pressure when hot, but pressure increases as you turn it to cold.

All other taps and showers in the house are still fine. The shower/tap was fine when first installed. The issue started a week after installation.

However, yesterday, for some bizarre reason the shower/tap started working normally again, ie pressure is inline with the other taps/showers in the house.

I am very perplexed by this and will continue to monitor, but it ties in with what you said about an airlock. I’m unsure though, why it would suddenly start and then suddenly stop.
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Postby stoneyboy » Tue Oct 27, 2020 10:24 pm

Hi webster2020
Fingers and legs crossed then!
Regards S
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Postby jonathanrubles » Thu Nov 12, 2020 7:13 am

It really depends where your source your water from. If you're on city water there's often a pressure regulator that can be adjusted with the right tool, likely requiring a plumber or your water utility to adjust.

If you have a well you've got more control over your pressure. Typically you'll have a pressure tank and an adjustable relay that cycles your pump on and off at certain pressures. You can adjust the pressure on the relay unit.
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