Shower pump - appears to have air ingress

[Michael L]

I fitted a Showermate Standard Twin to replace an old pump that had failed. The new pump had been purchased some five years earlier and not used. The pump sits at the end of the bath on the floor and I used some Hep20 pl astic pipe and 90 degree fittings to connect up. Cold supply is from a tank in the loft and hot from the CH fed hot water cylinder which sits on the s ame floor as the pump. Hot and cold are pumped. The pump ran perfectly for around six months but over the last couple, the pump has become noisy and fails to pump water until several seconds after I turn on the shower mixer. Usually after a couple of 'hiccups' it runs steadily delivering a good show er and with normal noise levels. I have taken photos of the installation but I cannot see how to post them. I could put them on a hosting site if useful.

[Graham.]

Can't help you with the plumbing but the normal way to use images is to upload them to flickr, tinypic etc etc and post the link here.

[David]

If air can get in then water can get out, presumably?

Are there any signs of water leakage anywhere along the pipe run?

It does sound as though air may be slowly leaking into the pipe(s) between the supply and the pump, so it takes a short while to 'prime' itself.

In which case, if air is leaking in, where is the water going to make space for it?

Alternatively there may be a poor seal against incoming air when the pump kicks off, which slowly seals under suction.

Either way, check all your joints!

Cheers

Dave R

[Andy Burns]

Is the hot taken from the normal outlet at the top of the tank, or from a special flange[*] on the side or top of the tank? These are designed to stop intake of air ...

[*] could be essex/warrix/tech/surrey type of flange.

[Capitol]

Another cause may be a sticking flow switch. I have known these to fail due to the magnet rusting and splitting the plastic sleeve around the Magnet.

[michael_lakeman]

I will check

[michael_lakeman]

I can't see any leakage and the pump ran ok for 6 months so doubt it could be a design issue. I wondered if seals in the pump could have deteriorated from sitting unused from years shortening their life. Can't see any sign of water leakage. Once the pump has settled the flow is steady. It does appea r though that air is being expelled in the water flow after start up.

[johnjessop46]

Check your cold feed from loft header tank to bottom of the cylinder is not obstructed and the shut off in the connecting pipe is fully open. Does your hot tap to the bath flow satisfactorily at fully open? Suspect a restriction to the flow may cause air to be drawn down the vent pipe if the feed to the booster pump is incorrectly connected to the hot water pipework to the taps.

[michael_lakeman]

d. The new pump had been purchased some five years earlier and not used.

plastic pipe and 90 degree fittings to connect up. Cold supply is from a ta nk in the loft and hot from the CH fed hot water cylinder which sits on the same floor as the pump. Hot and cold are pumped.

e pump has become noisy and fails

ower and with normal noise levels.

. I could put them on a hosting site if useful.

I checked the hot flow to the bath and it is fine. There is no special flan ge for the shower. The hot feed is a 22/22/22 tee off the pipe from the cyl inder. The gate valves are fully open and the shut off valves I added when I fitted the new pump are fully open. I have another problem which I am no w thinking could be connected. I get particles in my water supply. I notice d them some time after the pump problem however. They are orange or black g enerally. They do not appear to be affected by a magnet. We are filtering o ur drinking water until we can sort it out. The neighbour does not have thi s. We have a lead service pipe as far as I know - rising main is definitely lead. I think I should start another thread about this.

[David]

The reason for a flange on the side of your hot water cylinder near the top is that the take off at the top usually also acts as an expansion pipe which leads to a loop over the cold water tank in the loft and to open air.

So when you turn the pump on it tries to pull water out of the top of the tank via the pipe but some of the pull is bringing air down the overflow.

This can result in air being sucked into the hot feed.

Someone with more plumbing chops will be along shortly, but I suspect that when you start the pump the air starts to flow down the pipe more easily than the water starts to flow up out of the tank, but in a marginal situation once the hot water is flowing then the air is no longer drawn in (at least in any great quantity).

I wouldn't think that this has anything to do with particles in your drinking water. I do hope your drinking water comes directly from the mains and is not fed from the tank in the loft, which is a major hygiene risk.

Cheers

Dave R

[Tim+]

Just to be clear, is there a delay I. The pump motor starting when you open the tap or is it a delay in effective pumping?

If the motor is not actually starting straight away then that could be a faulty flow switch or poor flow through the pump.

Does the pump have small strainer filters on the inlets? Partial blockage might cause these problems.

If it's starting straight away but not effectively pumping this again may be due to partial blockage causing air entrainment via the expansion pipe or cavitation in the pump.

Tim

[michael_lakeman]

d. The new pump had been purchased some five years earlier and not used.

plastic pipe and 90 degree fittings to connect up. Cold supply is from a ta nk in the loft and hot from the CH fed hot water cylinder which sits on the same floor as the pump. Hot and cold are pumped.

e pump has become noisy and fails

ower and with normal noise levels.

. I could put them on a hosting site if useful.

Checked the pump docs - Expansion pipe: When the method of connection is to be made via the expansion pipe, the BASE of the cold water storage tank MUST be at least

1 metre above the connection/take off of the hot water storage cylinder fee ding the pump. There is >1metre.

[michael_lakeman]

The drinking water comes from the rising main. Looking at the Stuart Turner instructions again - looks like there are no filters. The instructions say they should be provided separately. I've just plumbed straight in/out of the pump with Hep2o. I have reported the particles to Severn Trent.

[Capitol]

Crud in the system will bugger up the flow valve movement. The clearances are quite small.

[michael_lakeman]

d. The new pump had been purchased some five years earlier and not used.

plastic pipe and 90 degree fittings to connect up. Cold supply is from a ta nk in the loft and hot from the CH fed hot water cylinder which sits on the same floor as the pump. Hot and cold are pumped.

e pump has become noisy and fails

ower and with normal noise levels.

. I could put them on a hosting site if useful.

In answer to Tim+ - the pump runs immediately the shower valve is operated but I just get the same flow as when the pump isn't powered up. After an in creasingly long delay it starts actively pumping.

[Tim+]

Sounds like it's air locked or cavitating. Impellers have been known to come loose on motor shafts too.

Tim

[michael_lakeman]

d. The new pump had been purchased some five years earlier and not used.

plastic pipe and 90 degree fittings to connect up. Cold supply is from a ta nk in the loft and hot from the CH fed hot water cylinder which sits on the same floor as the pump. Hot and cold are pumped.

e pump has become noisy and fails

ower and with normal noise levels.

. I could put them on a hosting site if useful.

I am probably going to change the pump after fitting either a strainer on e ach feed or else one on the hot water tank cold water feed. I am also going to try to ease the flow by buying some pre-formed hep2o bends.

[michael_lakeman]

d. The new pump had been purchased some five years earlier and not used.

plastic pipe and 90 degree fittings to connect up. Cold supply is from a ta nk in the loft and hot from the CH fed hot water cylinder which sits on the same floor as the pump. Hot and cold are pumped.

e pump has become noisy and fails

ower and with normal noise levels.

. I could put them on a hosting site if useful.

Correction - will form some bends in the Hep2o pipe.

[michael_lakeman]

d. The new pump had been purchased some five years earlier and not used.

plastic pipe and 90 degree fittings to connect up. Cold supply is from a ta nk in the loft and hot from the CH fed hot water cylinder which sits on the same floor as the pump. Hot and cold are pumped.

e pump has become noisy and fails

ower and with normal noise levels.

. I could put them on a hosting site if useful.

Just checked the flow rate with the pump turned off. Checked cold then hot and each roughly the same filling a 500ml jug after 17 seconds. Water alway s flows immediately when mixer is turned on so I would have thought an air block was ruled out as a cause of water pumping delay.

[Tim+]

Much as I (and possibly others) would like to help you, you do yourself no favours by just re-quoting your original message. This gives no context as to who you're responding to. The correct method is to quote enough of the message you're responding to to build a "conversation" as it were (but without re-quoting masses of irrelevant stuff).

Tim