Loss of pressure from gravity tank?

[yfs1]

Hello All,

First of all pardon my terminology but I am having an issue with my upstairs cold water. Basically when you turn the tap on it is as normal and within 1 second the pressure goes down to next to nothing. If you turn it off for 3 or 4 seconds, and turn it back on the same thing happens (It obviously builds up a little bit of pressure).

If you move the tap towards hot it works fine (but there is no mix)

Some observations/assumptions:

1.) It is happening with the sinks, toilets and bath upstairs. The power shower is fine but Im pretty sure that runs off the same supply as downstairs.

2.) We have had a water softening system for a few years so haven't had any issues with hard water

3.) I went up to the gravity tank, opened it and took a look inside. No sediment. There are three lines coming from it (Main Bathroom, Ensuite and Immersion??) and I stuck my finger in the line but no obvious blockage

4.) I checked all valves and everything is open (Except the pressure valve for the heating but that only gets turned on for a few seconds once in a while to increase the pressure to the radiators)

5.) I bled the radiators (A reach but I had nothing else to try).

It is a holiday weekend and this isn't critical but I would love some advice before ringing a plumber (and paying) on Tuesday

Thanks!

 

[crockett]

You could try to 'backfill' the offending section of pipework from the mains, as it seems you have a blockage in your pipework. Be careful in doing this though, and don't backfill for too long, either. maybe 10 seconds or so. Has worked for me in the past.

 

[yfs1]

Im assuming this would involve getting a garden hose up to the gravity tank, opening up the cold water taps, and holding it to the outlet within the tank andd turning it on?

If there is a blockage, is there a plunger type tool to use that would do the same job?

 

[crockett]

No. Hosepipe on tap spout, open up basin/bath tap (make sure its secure!) then open tap from mains supply. Force mains water back up pipe. Then switch off mains tap, and see if water flows more freely from basin/bath tap.

 

[yfs1]

That makes sense!

Ill try that today

 

[crockett]

Probably best to get someone with you, so they can turn the mains on while you're upstairs

 

[JohnD]

I went up to the gravity tank, opened it and took a look inside. No sediment. There are three lines coming from it (Main Bathroom, Ensuite and Immersion??)

Are you sure? And do all three of them have poor flow? If they have service valves, turn them off one at a time to see what they do, and hang labels on then when you know.

It seems very improbable that you would get an airlock or blockage in all three at the same time. See which has the problem.

Any signs of dead wildlife in the tank? Does it have a close-fitting lid?

 

[yfs1]

I went up to the gravity tank, opened it and took a look inside. No sediment. There are three lines coming from it (Main Bathroom, Ensuite and Immersion??)

Are you sure? And do all three of them have poor flow? If they have service valves, turn them off one at a time to see what they do, and hang labels on then when you know.

It seems very improbable that you would get an airlock or blockage in all three at the same time. See which has the problem.

Any signs of dead wildlife in the tank? Does it have a close-fitting lid?

The lid fits perfectly (The builders left it open so I had to request one). I did a wildlife check 2 years ago when I fit the top. I opened it back up when this issue started and clean as can be. Used a flashlight to make absolutely sure.

Unfortunately despite asking for them, service valves were not added to any of the sinks.

I tried holding the mains to the bathtub, heard a few "blubs" up in the attic but it didn't clear it. Could only hold it without leakage for 20-30 seconds. I will try it for longer once places open and I can get my hands on a rubber adapter.

Cheers

 

[yfs1]

I tried it again before putting the hose away. I held it as long as I possibly could. I heard about 7 "blubs" and then it stopped (even though the water was still making its way up).

It now works perfectly.

It seems it was air in the line after all. Not sure how that happened (I don't have a ton of confidence in the original plumber) but glad its sorted.

Thanks to Crockett as you probably saved me at least €60!

 

[crockett]

Glad it helped you YFS1. sometimes it's air, but mostly its bits of debris that build up.