Figure of Speech, Metaphor
The metaphor of pouring or flow of liquid, rainfall or spring is used to show the abundant quantity of something. Nothing of such process and metaphor contradicts the nature of God's Spirit. A spirit, holy or demonic, good or bad is by definition a person or personal entity. BDAG3 lexicon on έκχέω:
① cause to be emitted in quantity, pour out
ⓐ of liquids: water D 7:3. αἷμα ἐ. shed blood =commit a murder (αἷμα 2a) Ac 22:20; Ro 3:15 (Is 59:7; Ps 13:3); Rv 16:6; GJs 23:3 (1 Km 25:31); cp. AcPl Ha 11, 8. αἷμα ἐκχυννόμενον (Jos., Ant. 19, 94 αἷμα πολὺ ἐκκεχυμένον) Mt 23:35; cp. Lk 11:50; in the cultic sense pour out (cp. Lev 4:7), esp. of Jesus’ death (Orig., C. Cels. 8, 42, 33) 1 Cl 7:4. αἷμα ἐ. περὶ πολλῶν εἰς ἄφεσιν ἁμαρτιῶν blood shed for (the benefit of) many, for the forgiveness of sins Mt 26:28 (w. purpose indicated by εἰς as Lucian, Tim. 5 εἰς εὐεργεσίαν); αἷ. ἐ. ὑπὲρ πολλῶν Mk 14:24; cp. Lk 22:20. Wine ἐκχεῖται is spilled (out) (cp. Gen 38:9) Mt 9:17; cp. Mk 2:22 v.l.; cp. Lk 5:37; ἐ. φιάλην, as we say, pour out a bowl (i.e. its contents) Rv 16:1ff, 8, 10, 12, 17.
ⓑ of solid objects (Lev 4:12) ἐξεχύθη πάντα τὰ σπλάγχνα all his bowels gushed out Ac 1:18 (cp. Quint. Smyrn. 8, 302 ἔγκατα πάντʼ ἐχύθησαν; 9, 190; 2 Km 20:10; Jos., Bell. 7, 453; AcThom 33 [Aa II/2, 150, 19]). Of coins scatter on the ground J 2:15.
② cause to fully experience, pour out fig. ext. of 1 (cp. Lycophron 110 πόθον; Ps.-Demetr., Eloc. 134 τοῦ λόγου τὴν χάριν; Aelian, NA 7, 23 θυμόν; τὴν ὀργήν PsSol 2:24; ψυχὴν εἰς θάνατον 16:2; Philo, Spec. Leg. 1, 37 of light; Jos., Ant. 6, 271 φόνον) of the Holy Spirit which, acc. to Joel’s prophecy, is to pour down on people like rain (Jo 2:23; cp. 1QS 4:21): pour out (Iren. 5, 12, 2 [Harv II 351, 2]) Ac 2:33. ἐπί τινα (after Jo 3:1) 2:17f; 10:45; Tit 3:6; B 1:3; 1 Cl 46:6. The ref. to the Holy Spirit has perh. brought the idea of outpouring into Ro 5:5 ἡ ἀγάπη τ. θεοῦ ἐκκέχυται ἐν ταῖς καρδίαις ἡμῶν διὰ πνεύματος ἁγίου τοῦ δοθέντος ἡμῖν. But gener., whatever comes from above is connected w. this verb (Ps 44:3 χάρις; Sir 18:11 ἔλεος; Hos 5:10 ἐπʼ αὐτοὺς ἐκχεῶ ὡς ὕδωρ τὸ ὅρμημά μου; Philo, Aet. M. 147 ἄνωθεν ἐ.; TestLevi 18:5; ἐκχεῖσθαι … ὁ λόγος ἐπὶ πᾶσαν τὴν οἰκουμένην Orig., C. Cels. 6, 78, 26).
③ to give oneself totally in commitment, give oneself up to, dedicate oneself, pass. (Polyb. 31, 25, 4 εἰς ἑταίρας; Plut., Anton. 21, 1; Philo, Op. M. 80; TestReub 1:6; εἰς πράγματα ἀφροδισίακα Hippol., Ref. 4, 19, 2) w. dat. (Alciphron 3, 34, 1 τῷ γέλωτι) τῇ πλάνῃ τ. Βαλαάμ Jd 11. λίαν ἐ. ἀγαπῶν ὑμᾶς I am totally consumed w. affection for you = my affection for you streams out of me. IPhld 5:1.—M-M. TW.