Reduction in water pressure a couple weeks later?

[JT]

Hi folks. I'd appreciate some opinions.

We've recently had a loft conversion done, and at the start of the construction we had a main fed hot water system put in (Megaflo). Immediately after that was put in, I noticed a fantastic increase in the water pressure in the shower and all the taps around the house. The shower was barely useable at full blast.

Strangely, a couple weeks later the pressure dropped again. It was still pretty good but no where near as it was before, but it was useable so I didn't think twice about it.

Now that our loft conversion is finished, the water pressure up there is pretty poor, and downright unuseable if someone has a cold/hot tap on downstairs.

Unfortunately the plumber who put the original Megaflo system in has left now (went to Poland), so I can't ask him what he might have done to cause the reduction in pressure. We had another plumber come in and check it, and he says it's because of the 15mm copper piping we have from the mains (and wants us to spend a couple thousand upgrading that). That doesn't make sense to me because the pressure /used/ to be great for a couple of weeks.

I've checked the mains stop c*ck in the house and that's open fully, and I'm out of ideas now, other than consulting yet another plumber.

Could there have been something else during the construction that may have affected the water flow? Or what else can I try to find the bottleneck?

Thanks a lot, James

[Lobster]

Well, if it was formerly OK and suddenly dropped, then surely you're looking at a physical blockage somewhere, eg a bit of debris (left in the pipework by the plumber) having detached itself and migrated to somewhere critical. Is it just the loft shower that's got the problem? The shower valve is likely to have a filter on the incoming pipes; can you remove the valve and check that there's nothing in there?

David

[JT]

I noticed a drop in pressure in all taps around the house. A blockage somewhere would make sense, but if it's affecting all the taps, then it must be a blockage nearer the mains source. It seems a bit rubbish that our plumber that came to have a look didn't suggest that as a problem and just said 'nah, you've got to replace all the 15mm'.

The other thing is that it was good for a couple of weeks first. Is there a chance that some kind of debris could have broken off from somewhere inside the pipework?

Cheers, James

[Lobster]

Erm - that's what I suggested last time! But less plausible I suppose given that all the taps are affected; any blockage would be most likely to be at a bottlneck, ie a valve or tap.

David

[<me9]

If it's /all/ taps, cold as well, it could be that the water authority has introduced a programme to reduce leakage from its mains by pressure reduction. Have neighbouring properties been affected?

[Aidan]

JT wrote: There's a strainer/ filter on the inlet to the multi-function valve (strainer, reducing valve & check valve); I'm not certain that the Megaflo's got a PRV but you'll see at a glance. The strainer may have got blocked with crud left in the pipes. Check the pressure reducing valve (if there is one) is set at the correct pressure.

It should have been fitted by a registered installer, if not the warranty will be void. Read the installation manual ensure it's been installed correctly.

[Lobster]

But that wouldn't affect the cold mains pressure all over the house??

David

[Aidan]

If it's the usual multi-function valve with a balanced pressure draw-off for cold, then yes it would affect everything served by the hot & cold.

If not, or if it's not been piped correctly, then no. It's often a PITA to properly connect the cold to the PRV outlet, which will typically be above the ground floor. They often leave the cold connected to the ground floor mains supply.

[Harry Bloomfield]

JT expressed precisely :

Could the problem be outside your property?

Our pressure sometimes varies between two levels, we put it down to the water authority turning pumps on and off at the local water tower.

[JT]

Thanks for all the replies!

Aiden, I cleaned the strainer, and also recharged the air volume in the Megaflo, but that didn't seem to make much difference.

I suppose it /could/ be the water company changing something, and was just an unfortunate coincedence that it was just after we got our system newly setup!

[Aidan]

There is (should be) a pressure reducing valve on the Megaflo; it should be factory set to deliver 3 bar outlet pressure. It won't do this if the inlet pressure is less than 3 bar. Your problem is most likely caused by a reduction in inlet pressure (i.e., reduced mains pressure), or a defective or incorrectly set PRV. You'd need to get hold of a pressure gauge to diagnose the problem.

If it had been a restriction, as I'd suggested, then the pressure would creep up to the set PRV outlet pressure when there was no flow, compressing the gas charge in the top of the heater. You'd then get an initial 'burst' of flow at 'normal' high pressure, dropping off as the air expanded and the flow rate from the mains declined. Sorry to contradict myself.

You could check that neither of the 2 pressure relief valves are discharging water. The discharge tundish (usually black plastic) should be visible, so this should be immediately obvious.

If it's reduced mains pressure (< 3bar at the PRV inlet), you could also contact the water supplier to enquire about the recent reduction in pressure. They're not obliged to supply much pressure, so they may have turned it down. It might also be caused by a large underground leak and they'd want to know.

[JT]

Sorry, I didn't entirely understand all that. However, when I do turn on a tap or shower, there /is/ and initial burst of air/water coming out. After a few seconds it stabilises at a slower rate. What did you mean that this implies?

There isn't any sign of discharge.

I think this might have to be my next step. Unfortunately it's difficult for me to come up with specific dates that the pressure went down because I didn't take much notice back then. I suppose I could just get a reading from the water company and check that it's the same as what's coming through to my house?

Thanks a lot, James

[Aidan]

There will be, it is the nature of the system.

The question is whether the initital surge/burst is at the same sort of pressure as the surge/burst was when the system was first installed. If so, this would suggest a restriction, i.e., adequate static pressure but inadequate pressure & flow rate when you're drawing off water.

If not, it suggests low pressure (less than 3 bar) at the inlet to the heater/ outlet of the PRV. That would be low mains pressure or low outlet pressure from the PRV; gauges are needed to determine which.

Good.

I fear you'll probably get shunted from one useless minion to another, but it's worth trying. You could ask your neighbours if they've noticed a pressure drop. It won't much affect thoose with traditional tank-fed systems, so they may not have noticed.